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What Caffeine Does To Your BrainCaffeine and power output -
Defining training and performance caliber : A participant classification framework. International Journal of Sports Physiology and Performance. Overtraining Syndrome OTS and Relative Energy Deficiency in Sport RED-S : Shared pathways, symptoms and complexities Stellingwerff, Trent, Heikura, Ida A.
Overtraining Syndrome OTS and Relative Energy Deficiency in Sport RED-S : Shared pathways, symptoms and complexities. The effects of an acute "train-low" nutritional protocol on markers of recovery otpimization in endurance-trained male athletes Russo, Isabella, Della Gatta, Paul A.
and Costa, Ricardo J. The effects of an acute "train-low" nutritional protocol on markers of recovery otpimization in endurance-trained male athletes. Dietary manipulation for optimizing endurance training adaptations and performance : Carbohydrate vs. fat Whitfield, Jamie and Burke, Louise M.. In In Tiidus, Peter M.
and Josse, Andrea R. The Routledge handbook on biochemistry of exercise pp. Isolated and combined effects of highintensity interval training and timerestricted eating on glycaemic control in reproductive-aged women with overweight or obesity : Study protocol for a four-armed randomised controlled trial Moholdt, Trine, Silva, Catalina P.
Isolated and combined effects of highintensity interval training and timerestricted eating on glycaemic control in reproductive-aged women with overweight or obesity : Study protocol for a four-armed randomised controlled trial.
BMJ Open. Article e UEFA expert group statement on nutrition in elite football Collins, James, Maughan, Ronald John, Gleeson, Mike, Bilsborough, Johann, Jeukendrup, Asker, Morton, James P. McCall, Alan. UEFA expert group statement on nutrition in elite football.
British Journal of Sports Medicine. Mimicking exercise : What matters most and where to next? Hawley, John A. and Green, Daniel J.. The Journal of Physiology. Nutritional approaches to counter performance constraints in high level sports competition Burke, Louise M.. Nutritional approaches to counter performance constraints in high level sports competition.
Experimental Physiology. ACSM expert consensus statement on weight loss in weight-category sports Burke, Louise M. ACSM expert consensus statement on weight loss in weight-category sports. Current Sports Medicine Reports. International Society of Sports Nutrition position stand : Sodium bicarbonate and exercise performance Grgic, Jozo, Pedisic, Zeljko, Saunders, Bryan, Artioli, Guilherme G.
International Society of Sports Nutrition position stand : Sodium bicarbonate and exercise performance. Journal of the International Society of Sports Nutrition.
Article: Mice with whole-body disruption of AMPK-glycogen binding have increased adiposity, reduced fat oxidation and altered tissue glycogen dynamics Janzen, Natalie, Whitfield, Jamie, Murray-Segal, Lisa, Kemp, Bruce E. Mice with whole-body disruption of AMPK-glycogen binding have increased adiposity, reduced fat oxidation and altered tissue glycogen dynamics.
International Journal of Molecular Sciences. Neither beetroot juice supplementation nor increased carbohydrate oxidation enhance economy of prolonged exercise in elite race walkers Burke, Louise M. Neither beetroot juice supplementation nor increased carbohydrate oxidation enhance economy of prolonged exercise in elite race walkers.
The validity of ultrasound technology in providing an indirect estimate of muscle glycogen concentrations is equivocal Bone, Julia L. The validity of ultrasound technology in providing an indirect estimate of muscle glycogen concentrations is equivocal.
Skeletal muscle adaptive responses to different types of short-term exercise training and detraining in middle-age men Callahan, Marcus J. and Camera, Donny M.. Skeletal muscle adaptive responses to different types of short-term exercise training and detraining in middle-age men.
Ketogenic low-CHO, high-fat diet : The future of elite endurance sport? Burke, Louise. Athlete health and safety at large sport events : The development of consensus-driven guidelines Mountjoy, Margo, Moran, Jane, Ahmed, Hosny, Bermon, Stephane, Bigard, Xavier, Doerr, Dominik, Lacoste, Alain, Miller, Stuart, Weber, Alexis, Foster, Jeremy, Budgett, Richard, Engebretsen, Lars, Burke, Louise M.
Athlete health and safety at large sport events : The development of consensus-driven guidelines. Postexercise hot-water immersion does not further enhance heat adaptation or performance in endurance athletes training in a hot environment Stevens, Christopher J.
and Burke, Louise. Postexercise hot-water immersion does not further enhance heat adaptation or performance in endurance athletes training in a hot environment. Lower nocturnal blood glucose response to a potato-based mixed evening meal compared to rice in individuals with type 2 diabetes Devlin, Brooke L.
Lower nocturnal blood glucose response to a potato-based mixed evening meal compared to rice in individuals with type 2 diabetes. Clinical Nutrition.
Quinine ingestion during the latter stages of a 3,m time trial fails to improve cycling performance Etxebarria, Naroa, Clark, Brad, Ross, Megan L. Quinine ingestion during the latter stages of a 3,m time trial fails to improve cycling performance.
Acute ketogenic diet and ketone ester supplementation impairs race walk performance Whitfield, Jamie, Burke, Louise M. Acute ketogenic diet and ketone ester supplementation impairs race walk performance. Does the nutritional composition of dairy milk based recovery beverages influence post-exercise gastrointestinal and immune status, and subsequent markers of recovery optimisation in response to high intensity interval exercise?
Russo, Isabella, Della Gatta, Paul A. Frontiers in Nutrition. Can high-intensity interval training promote skeletal muscle anabolism? Callahan, Marcus J. Assessing overall exercise recovery processes using carbohydrate and carbohydrate-protein containing recovery beverages Russo, Isabella, Della Gatta, Paul A.
Assessing overall exercise recovery processes using carbohydrate and carbohydrate-protein containing recovery beverages.
Prevalence of impaired physiological function consistent with Relative Energy Deficiency in Sport RED-S : An Australian elite and pre-elite cohort Rogers, Margot Anne, Appaneal, Renee Newcomer, Hughes, David, Vlahovich, Nicole, Waddington, Gordon, Burke, Louise M.
and Drew, Michael. Prevalence of impaired physiological function consistent with Relative Energy Deficiency in Sport RED-S : An Australian elite and pre-elite cohort.
Sustained Exposure to High Carbohydrate Availability Does Not Influence Iron-Regulatory Responses in Elite Endurance Athletes McKay, A. and Burke, L.. Sustained Exposure to High Carbohydrate Availability Does Not Influence Iron-Regulatory Responses in Elite Endurance Athletes.
Chronic pantothenic acid supplementation does not affect muscle coenzyme A content or cycling performance Whitfield, Jamie, Harris, Roger C. Chronic pantothenic acid supplementation does not affect muscle coenzyme A content or cycling performance.
Applied Physiology, Nutrition and Metabolism. Adaptation to Low Carbohydrate High Fat diet is rapid but impairs endurance exercise metabolism and performance despite enhanced glycogen availability Burke, Louise M.
and Sharma, Avish P.. Adaptation to Low Carbohydrate High Fat diet is rapid but impairs endurance exercise metabolism and performance despite enhanced glycogen availability. Journal of Physiology. Nutrition for sport and physical activity Burke, Louise M. and Manore, Melinda M.. Nutrition for sport and physical activity.
In In Marriott, Bernadette P. and Yates, Allison A. Present knowledge in nutrition : Clinical and applied topics in nutrition ; volume 2 pp. Body composition of elite Olympic combat sport athletes Slater, Gary, Cox, Gregory R.
and Reale, Reid. Body composition of elite Olympic combat sport athletes. European Journal of Sport Science. Nutrition strategies for triathlon Burke, Louise M.
Nutrition strategies for triathlon. In In Migliorini, Sergio Ed. Triathlon medicine pp. The Australian Institute of Sport AIS and NationalEating Disorders Collaboration NEDC positionstatement on disordered eating in highperformance sport Wells, Kimberley, Jeacocke, Nikki, Appaneal, Renee, Smith, Hillary, Vlahovich, Nicole, Burke, Louise Mary and Hughes, David.
The Australian Institute of Sport AIS and NationalEating Disorders Collaboration NEDC positionstatement on disordered eating in highperformance sport. Chrono-nutrition for the prevention and treatment of obesity and type 2 diabetes : From mice to men Hawley, John A.
Chrono-nutrition for the prevention and treatment of obesity and type 2 diabetes : From mice to men. Maternal lifestyle interventions : Targeting preconception health Moholdt, Trine and Hawley, John A.. Maternal lifestyle interventions : Targeting preconception health.
Trends in Endocrinology and Metabolism. PRESENT : Text that develops the checklist for the adequate report of the evidence in clinical trials of sport and exercise nutrition English-Spanish translation Betts, James A.
PRESENT : Text that develops the checklist for the adequate report of the evidence in clinical trials of sport and exercise nutrition English-Spanish translation.
Revista Andaluza de Medicina del Deporte. Iron metabolism : Interactions with energy and carbohydrate availability McKay, Alannah K. and Peeling, Peter. Iron metabolism : Interactions with energy and carbohydrate availability. The influence of biological sex and fitness status on markers of recovery optimisation in response to prolonged high intensity interval exercise Russo, Isabella, Della Gatta, P.
The influence of biological sex and fitness status on markers of recovery optimisation in response to prolonged high intensity interval exercise. International Journal of Sports Science.
Time-restricted eating as a nutrition strategy for individuals with type 3 diabetes : A feasibility study Parr, Evelyn B. Time-restricted eating as a nutrition strategy for individuals with type 3 diabetes : A feasibility study. Circulating and adipose tissue miRNAs in women with polycystic ovary syndrome and responses to high-intensity interval training Lionett,Sofie, Kiel,Ida A.
and Moholdt,Trine. Circulating and adipose tissue miRNAs in women with polycystic ovary syndrome and responses to high-intensity interval training. Omega-3 polyunsaturated fatty acids mitigate palmitate-induced impairments in skeletal muscle cell viability and differentiation Tachtsis, Bill, Whitfield, Jamie, Hawley, John A.
Omega-3 polyunsaturated fatty acids mitigate palmitate-induced impairments in skeletal muscle cell viability and differentiation. The Challenge of Maintaining Metabolic Health During a Global Pandemic Andy J.
King, Louise M. Burke, Shona L. Halson and John A. The Challenge of Maintaining Metabolic Health During a Global Pandemic. Sports Dietitians Australia Position Statement: Nutrition for Exercise in Hot Environments Alan J McCubbin, Bethanie A Allanson, Joanne N Caldwell Odgers, Michelle M Cort, Ricardo J S Costa, Gregory R.
Cox, Siobhan Crawshay, Ben Desbrow, Eliza G Freney, Stephanie K Gaskell, David Hughes, Chris Irwin, Ollie Jay, Benita Lalor, Meg Ross, Gregory Shaw, Julien Periard and Louise Burke. Sports Dietitians Australia Position Statement: Nutrition for Exercise in Hot Environments. PRESENT Text Expanding on the Checklist for Proper Reporting of Evidence in Sport and Exercise Nutrition Trials James A.
Betts, Javier T. Gonzalez, Louise Burke, Graeme L. Close, Ina Garthe, Lewis J James, Asker E Jeukendrup, James P. Morton, David C Nieman, Peter Peeling, Stuart M Phillips, Trent Stellingwerff, Lucas Van Loon, Clyde Williams, Kathleen Woolf, Ronald J.
Maughan and Greg Atkinson. PRESENT Text Expanding on the Checklist for Proper Reporting of Evidence in Sport and Exercise Nutrition Trials. Microbiota and muscle highway - two way traffic John Hawley. Microbiota and muscle highway - two way traffic.
Key viral immune genes and pathways identify elite athletes with URS Colbey, Candice, Drew, Michael K. and West, Nicholas P. Key viral immune genes and pathways identify elite athletes with URS. Exercise Immunology Review.
Inflammation and oral contraceptive use in female athletes before the Rio Olympic Games Larsen, Brianna, Cox, Amanda, Colbey, Candice, Drew, Michael, McGuire, Helen, Fazekas de St Groth, Barbara, Hughes, David, Vlahovich, Nicole, Waddington, Gordon, Burke, Louise, Lundy, Bronwen, West, Nicholas and Minahan, Clare.
Inflammation and oral contraceptive use in female athletes before the Rio Olympic Games. Does high cardiorespiratory fitness confer some protection against pro-inflammatory responses after infection by SARS-CoV-2? Zbinden-Foncea, Hermann, Francaux, Marc, Deldicque, Louise and Hawley, John A..
A time to eat and a time to exercise Parr, Evelyn B. A time to eat and a time to exercise. Exercise and Sport Sciences Reviews. Genetic loss of AMPK-glycogen binding destabilizes AMPK and disrupts metabolism Hoffman, Nolan J.
Genetic loss of AMPK-glycogen binding destabilizes AMPK and disrupts metabolism. Molecular Metabolism. Time-restricted feeding alters lipid and amino acid metabolite rhythmicity without perturbing clock gene expression Leonidas S Lundell, Evelyn Parr, Brooke Devlin, Lars R Ingerslev, Ali Altintas, Shogo Sato, Paolo Sassone-Corsi, Romain Barres, Juleen R Zierath and John Hawley.
Time-restricted feeding alters lipid and amino acid metabolite rhythmicity without perturbing clock gene expression. Nature Communications. Divergent regulation of myotube formation and gene expression by E2 and EPA during in-vitro differentiation of C2C12 myoblasts Lacham-Kaplan, Orly, Camera, Donny and Hawley, John.
Divergent regulation of myotube formation and gene expression by E2 and EPA during in-vitro differentiation of C2C12 myoblasts.
Crisis of confidence averted : Impairment of exercise economy and performance in elite race walkers by ketogenic low carbohydrate, high fat LCHF diet is reproducible Burke, Louise M. Crisis of confidence averted : Impairment of exercise economy and performance in elite race walkers by ketogenic low carbohydrate, high fat LCHF diet is reproducible.
PLoS ONE. Core temperature responses to elite racewalking competition Stevens, Christopher John, Ross, Megan L. Core temperature responses to elite racewalking competition. Carbohydrate hydrogel products do not improve performance or gastrointestinal distress during moderate-intensity endurance exercise King, Andy J.
Carbohydrate hydrogel products do not improve performance or gastrointestinal distress during moderate-intensity endurance exercise. Influence of periodizing dietary carbohydrate on iron regulation and immune function in elite triathletes McKay, Alannah K. Influence of periodizing dietary carbohydrate on iron regulation and immune function in elite triathletes.
Principles of sports nutrition Broad, Elizabeth and Burke, Louise. Principles of sports nutrition. In In Broad, Elizabeth Ed. Sports nutrition for Paralympic athletes pp. Supplements for Optimal Sports Performance Burke, Louise.
Supplements for Optimal Sports Performance. Current Opinion in Physiology. Practical Hydration Solutions for Sport Luke N Belval, Yuri Hosokawa, Douglas J Casa, William M Adams, Lawrence E Armstrong, Lindsay B Baker, Louise Burke, Samuel Cheuvront, George Chiampas, Jose Gonzalez-Alonso, Robert A Huggins, Stavrous A Kavouras, Elaine C Lee, Brendon P McDermott, Kevin Miller, Zachary Schlader, Stacy Sims, Rebecca L Stearns, Chris Troyanos and Jonathan Wingo.
Practical Hydration Solutions for Sport. Nutrition and Altitude: Strategies to Enhance Adaptation, Improve Performance and Maintain Health: A Narrative Review Trent Stellingwerff, Peter Peeling, Laura Lewis, Rebecca Hall, Anu Koivisto, Ida A Heikura and Louise Burke.
Nutrition and Altitude: Strategies to Enhance Adaptation, Improve Performance and Maintain Health: A Narrative Review. Muscle glycogen utilization during an Australian Rules Football game Routledge, Harry E.
Muscle glycogen utilization during an Australian Rules Football game. Editorial: Cross Adaptation and Cross Tolerance in Human Health and Disease Ben James Lee, Oliver R Gibson, Charles Douglas Thake, Mike Tipton, John Hawley and James D Cotter.
Editorial: Cross Adaptation and Cross Tolerance in Human Health and Disease. Nutrition for travel : From jet lag to catering Halson, Shona L. and Pearce, Jeni. Nutrition for travel : From jet lag to catering.
International Association of Athletics Federations Consensus Statement Nutrition for Athletics Louise M. Burke, Linda M.
Castell, Douglas J. Casa, Graeme L. Close, Ricardo J. Costa, Ben Desbrow, Shona L. Halson, Dana M. Lis, Anna K. Melin, Peter Peeling, Philo U. Saunders, Gary J. Slater, Jennifer Sygo, Oliver C. Witard, Stéphane Bermon and Trent Stellingwerff.
International Association of Athletics Federations Consensus Statement Nutrition for Athletics. Contemporary nutrition strategies to optimize performance in distance runners and race walkers Burke, Louise M. and Mooses, Martin. Contemporary nutrition strategies to optimize performance in distance runners and race walkers.
Between-meal sucrose-sweetened beverage consumption impairs glycaemia and lipid metabolism during prolonged sitting : A randomized controlled trial Varsamis, Pia, Formosa, Melissa F. and Kingwell, Bronwyn A.. Between-meal sucrose-sweetened beverage consumption impairs glycaemia and lipid metabolism during prolonged sitting : A randomized controlled trial.
A framework for periodized nutrition for athletics Stellingwerff, Trent, Morton, James P. A framework for periodized nutrition for athletics.
Oral supplementation of specific collagen peptides combined with calf-strengthening exercises enhances function and reduces pain in achilles tendinopathy patients Praet, Stephan F.
Oral supplementation of specific collagen peptides combined with calf-strengthening exercises enhances function and reduces pain in achilles tendinopathy patients.
Hydration in sport and exercise Burke, Louise. Hydration in sport and exercise. In In J. Périard and S. Racinais Ed. Heat stress in sport and exercise pp.
The impact of chronic carbohydrate manipulation on mucosal immunity in elite endurance athletes McKay, Alannah K. The impact of chronic carbohydrate manipulation on mucosal immunity in elite endurance athletes. Journal of Sports Sciences.
A single bout of strenuous exercise overcomes lipid-induced anabolic resistance to protein ingestion in overweight, middle-aged men Smiles, William J.
A single bout of strenuous exercise overcomes lipid-induced anabolic resistance to protein ingestion in overweight, middle-aged men. The FASEB Journal. Nutrition and altitude: Strategies to enhance adaptation, improve performance and maintain health: A narrative review.
Winter peaks in heart failure: An inevitable or preventable consequence of seasonal vulnerability? Stewart, Simon, Moholdt, Trine T. Cardiac Failure Review. Ingesting a bitter solution: The sweet touch to increasing short-term cycling performance Etxebarria, Naroa, Ross, Megan L.
Ingesting a bitter solution: The sweet touch to increasing short-term cycling performance. The effects of dietary pattern during intensified training on stool microbiota of elite race walkers Murtaza, Nida, Burke, Louise M.
The effects of dietary pattern during intensified training on stool microbiota of elite race walkers. Prevalence and profile of "seasonal frequent flyers" with chronic heart disease: Analysis of patients and patient-years follow-up Loader, Jordan, Chan, Yih-Kai, Hawley, John A.
and Stewart, Simon. Prevalence and profile of "seasonal frequent flyers" with chronic heart disease: Analysis of patients and patient-years follow-up.
International Journal of Cardiology. Plasma amino acid concentrations after the ingestion of dairy and collagen proteins, in healthy active males Alcock, Rebekah D. Plasma amino acid concentrations after the ingestion of dairy and collagen proteins, in healthy active males.
Systematic Literature Review: The Effect of Dairy Milk on Markers of Recovery Optimisation in Response to Endurance Exercise Russo, Isabella, Camoes-Costa, Vera, Gaskell, Stephanie K.
Systematic Literature Review: The Effect of Dairy Milk on Markers of Recovery Optimisation in Response to Endurance Exercise.
The effect of beetroot juice supplementation on repeat-sprint performance in hypoxia Kent, Georgina L. The effect of beetroot juice supplementation on repeat-sprint performance in hypoxia. Acute carbohydrate ingestion does not influence the post-exercise iron-regulatory response in elite keto-adapted race walkers McKay, Alannah K.
Acute carbohydrate ingestion does not influence the post-exercise iron-regulatory response in elite keto-adapted race walkers. Racing weight and resistance training: Perceptions and practices in trained male cyclists Hoon, Matthew W.
Racing weight and resistance training: Perceptions and practices in trained male cyclists. The Physician and Sportsmedicine. Macronutrient periodisation Burke, Louise M.. Macronutrient periodisation. In In R. Belski, A.
Forsyth and E. Mantzioris Ed. Nutrition for sport, exercise and performance: A practical guide for students, sports enthusiasts and professionals pp. Urinary hydroxyproline is only suitable as a biomarker for acute intake, upt to 6 hours post ingestion of collagen proteins in "free-living", healthy, active males Alcock, Rebekah D.
Urinary hydroxyproline is only suitable as a biomarker for acute intake, upt to 6 hours post ingestion of collagen proteins in "free-living", healthy, active males.
Analysis of the effects of dietary pattern on the oral microbiome of elite endurance athletes Murtaza, Nida, Burke, Louise M. Analysis of the effects of dietary pattern on the oral microbiome of elite endurance athletes.
Alternate-day low energy availability during Spring Classics in professional cyclists Heikura, Ida A. Alternate-day low energy availability during Spring Classics in professional cyclists.
Chronic adherence to a ketogenic diet modifies iron metabolism in elite athletes McKay, Alannah K. Chronic adherence to a ketogenic diet modifies iron metabolism in elite athletes. Sports foods and dietary supplements for optimal function and performance enhancement in track and field athletes Peeling, Peter, Castell, Linda M.
Sports foods and dietary supplements for optimal function and performance enhancement in track and field athletes. Bone broth unlikely to provide reliable concentrations of collagen precursors compared with supplemental sources of collagen used in collagen research Alcock, Rebekah D.
Bone broth unlikely to provide reliable concentrations of collagen precursors compared with supplemental sources of collagen used in collagen research. Assessment of nutrient status in athletes and the need for supplementation Larson-Meyer, D.
Enette, Woolf, Kathleen and Burke, Louise. Assessment of nutrient status in athletes and the need for supplementation. Effects of providing high-fat versus high-carbohydrate meals on daily and postprandial physical activity and glucose patterns: a randomised controlled trial Parr, Evelyn, Devlin, Brooke, Callahan, Marcus J.
Effects of providing high-fat versus high-carbohydrate meals on daily and postprandial physical activity and glucose patterns: a randomised controlled trial.
Impact of first meal size during prolonged sitting on postprandial glycaemia in individuals with prediabetes: a randomised, crossover study Parr, Evelyn, Devlin, Brooke, Pinto, Samuel, Dunstan, David and Hawley, John.
Impact of first meal size during prolonged sitting on postprandial glycaemia in individuals with prediabetes: a randomised, crossover study.
An integrated, multifactorial approach to periodization for optimal performance in individual and team sports Mujika, Iñigo, Halson, Shona, Burke, Louise M. An integrated, multifactorial approach to periodization for optimal performance in individual and team sports.
Evidence-based supplements for the enhancement of athletic performance Peeling, Peter, Binnie, Martyn J. Evidence-based supplements for the enhancement of athletic performance.
IOC consensus statement on relative energy deficiency in sport RED-S : update Mountjoy, Margo, Sundgot-Borgen, J. IOC consensus statement on relative energy deficiency in sport RED-S : update.
Effects of creatine and carbohydrate loading on cycling time trial performance Tomcik, Kristyen A. Effects of creatine and carbohydrate loading on cycling time trial performance.
Sending the signal: Muscle glycogen availability as a regulator of training adaptation Hawley, John A.. Sending the signal: Muscle glycogen availability as a regulator of training adaptation.
In In B. Spiegelman Ed. Hormones, metabolism and the benefits of exercise pp. IOC consensus statement: dietary supplements and the high-performance athlete Maughan, Ronald J. Engebretsen, Lars. IOC consensus statement: dietary supplements and the high-performance athlete Organization of dietary control for nutrition-training intervention involving periodized carbohydrate availability and ketogenic low-carbohydrate high-fat diet Mirtschin, Joanne G.
Organization of dietary control for nutrition-training intervention involving periodized carbohydrate availability and ketogenic low-carbohydrate high-fat diet. Swifter, higher, stronger: what's on the menu?
Burke, Louise M. Effect of dietary nitrate supplementation on thermoregulatory and cardiovascular responses to submaximal cycling in the heat Kent, Georgina L. Effect of dietary nitrate supplementation on thermoregulatory and cardiovascular responses to submaximal cycling in the heat.
European Journal of Applied Physiology. No difference in young adult athletes' resting energy expenditure when measured under inpatient or outpatient conditions Bone, Julia L.
No difference in young adult athletes' resting energy expenditure when measured under inpatient or outpatient conditions. Chronic ketogenic low carbohydrate high fat diet has minimal effects on acid-base status in elite athletes Carr, Amelia J.
Chronic ketogenic low carbohydrate high fat diet has minimal effects on acid-base status in elite athletes. IOC Consensus Statement: Dietary Supplements and the High-Performance Athlete Maughan, Ronald J. IOC Consensus Statement: Dietary Supplements and the High-Performance Athlete.
Effect of resistance training and protein intake pattern on myofibrillar protein synthesis and proteome kinetics in older men in energy restriction Murphy, Caoileann, Shankaran, Mahalakshmi, Churchward-Venne, T.
Effect of resistance training and protein intake pattern on myofibrillar protein synthesis and proteome kinetics in older men in energy restriction. Weight management practices of Australian Olympic combat sport athletes Reale, Reid, Slater, Gary and Burke, Louise.
Weight management practices of Australian Olympic combat sport athletes. International Olympic Committee IOC consensus statement on relative energy deficiency in sport RED-S : update Mountjoy, Margo, Sundgot-Borgen, J.
International Olympic Committee IOC consensus statement on relative energy deficiency in sport RED-S : update. Protein availability and satellite cell dynamics in skeletal muscle Shamim, Baubak, Hawley, John and Camera, Donny. Protein availability and satellite cell dynamics in skeletal muscle.
Pitfalls of conducting and interpreting estimates of energy availability in free-living athletes Burke, Louise, Lundy, Bronwen, Fahrenholtz, Ida L. and Melin, Anna. Pitfalls of conducting and interpreting estimates of energy availability in free-living athletes.
The effect of water loading on acute weight loss following fluid restriction in combat sports athletes Reale, Reid, Slater, Gary, Cox, Gregory R. The effect of water loading on acute weight loss following fluid restriction in combat sports athletes. Low energy availability is difficult to assess but outcomes have large impact on bone injury rates in elite distance athletes Heikura, Ida A.
Low energy availability is difficult to assess but outcomes have large impact on bone injury rates in elite distance athletes. Human metabolomics reveal daily variations under nutritional challenges specific to serum and skeletal muscle Sato, Shogo, Evelyn, Parr B.
and Sassone-Corsi, Paolo. Human metabolomics reveal daily variations under nutritional challenges specific to serum and skeletal muscle. Toward a common understanding of diet-exercise strategies to manipulate fuel availability for training and competition preparation in endurance sport Burke, Louise, Hawley, John, Jeukendrup, A.
and Maughan, Ronald J.. Toward a common understanding of diet-exercise strategies to manipulate fuel availability for training and competition preparation in endurance sport. Methodologies for investigating performance changes with supplement use Burke, Louise and Peeling, Peter.
Methodologies for investigating performance changes with supplement use. Relative energy deficiency in sport in male athletes: a commentary on its presentation among selected groups of male athletes Burke, Louise, Close, Graeme L.
and Tenforde, Adam S.. Relative energy deficiency in sport in male athletes: a commentary on its presentation among selected groups of male athletes. Molecular basis of exercise-induced skeletal muscle mitochondrial biogenesis: Historical advances, current knowledge, and future challenges Perry, Christopher G.
and Hawley, John. Molecular basis of exercise-induced skeletal muscle mitochondrial biogenesis: Historical advances, current knowledge, and future challenges. Cold Spring Harbor Perspectives in Medicine. Adaptations to concurrent training in combination with high protein availability: A comparative trial in healthy, recreationally active men Shamim, Baubak, Devlin, Brooke L.
Adaptations to concurrent training in combination with high protein availability: A comparative trial in healthy, recreationally active men. High dietary fat intake increases fat oxidation and reduces skeletal muscle mitochondrial respiration in trained humans Leckey, Jill J.
High dietary fat intake increases fat oxidation and reduces skeletal muscle mitochondrial respiration in trained humans. FASEB Journal. Impact of energy availability, health, and sex on hemoglobin-mass responses following live-high-train-high altitude training in elite female and male distance athletes Heikura, Ida A.
and Stellingwerff, Trent. Impact of energy availability, health, and sex on hemoglobin-mass responses following live-high-train-high altitude training in elite female and male distance athletes.
Maximizing cellular adaptation to endurance exercise in skeletal muscle Hawley, John, Lundby, Carsten, Cotter, James D. Maximizing cellular adaptation to endurance exercise in skeletal muscle. Self-reported periodization of nutrition in elite female and male runners and race walkers Heikura, Ida, Stellingwerff, Trent and Burke, Louise.
Self-reported periodization of nutrition in elite female and male runners and race walkers. A multifactorial evaluation of illness risk factors in athletes preparing for the Summer Olympic Games Drew, Michael K.
and Waddington, Gordon. A multifactorial evaluation of illness risk factors in athletes preparing for the Summer Olympic Games. Reflections on the Position Stand: Nutrition and athletic performance Burke, Louise.
Reflections on the Position Stand: Nutrition and athletic performance. ACS M's Health and Fitness Journal. Post-exercise muscle glycogen resynthesis in humans Burke, Louise M. Post-exercise muscle glycogen resynthesis in humans. Ketone diester ingestion impairs time-trial performance in professional cyclists Leckey, Jill J.
Ketone diester ingestion impairs time-trial performance in professional cyclists. Fenugreek increases insulin-stimulated creatine content in l6C11 muscle myotubes Tomcik, Kristyen, Smiles, William, Camera, Donny, Hugel, Helmut M.
Fenugreek increases insulin-stimulated creatine content in l6C11 muscle myotubes. European Journal of Nutrition. Dietary nitrate supplementation does not improve cycling time-trial performance in the heat Kent, Georgina L.
Dietary nitrate supplementation does not improve cycling time-trial performance in the heat. Acute low-intensity cycling with blood-flow restriction has no effect on metabolic signaling in human skeletal muscle compared to traditional exercise Smiles, William J. Acute low-intensity cycling with blood-flow restriction has no effect on metabolic signaling in human skeletal muscle compared to traditional exercise.
Single and combined effects of beetroot crystals and sodium bicarbonate on 4-km cycling time trial performance Callahan, Marcus J. Single and combined effects of beetroot crystals and sodium bicarbonate on 4-km cycling time trial performance.
Factors influencing the post-exercise hepcidin response in elite athletes Peeling, P. Factors influencing the post-exercise hepcidin response in elite athletes. Postexercise muscle glycogen resynthesis in humans Burke, Louise, Van Loon, Luc and Hawley, John. Postexercise muscle glycogen resynthesis in humans.
Individualised dietary strategies for Olympic combat sports: Acute weight loss, recovery and competition nutrition Reale, Reid, Slater, Gary and Burke, Louise M.. Individualised dietary strategies for Olympic combat sports: Acute weight loss, recovery and competition nutrition.
Acute-weight-loss strategies for combat sports and applications to Olympic success Reale, Reid, Slater, Gary and Burke, Louise M.. Acute-weight-loss strategies for combat sports and applications to Olympic success. A mismatch between athlete practice and current sports nutrition guidelines among elite female and male middle- and long-distance athletes Heikura, Ida A.
A mismatch between athlete practice and current sports nutrition guidelines among elite female and male middle- and long-distance athletes.
Zierath, M. Joyner and J. Hawley Ed. The biology of exercise: A subject collection from Cold Spring Harbor Persepectives in Medicine pp. Prevalence of illness, poor mental health and sleep quality and low energy availability prior to the Summer Olympic Games Drew, Michael, Vlahovich, Nicole, Hughes, David, Appaneal, Renee, Burke, Louise, Lundy, Bronwen, Rogers, Margot, Toomey, Mary, Watts, David, Lovell, Gregory, Praet, Stephan F.
Prevalence of illness, poor mental health and sleep quality and low energy availability prior to the Summer Olympic Games. Manipulation of muscle creatine and glycogen changes DXA estimates of body composition Bone, Julia L.
Manipulation of muscle creatine and glycogen changes DXA estimates of body composition. Concurrent exercise training: Do opposites distract? Coffey, Vernon and Hawley, John. Dietary microperiodization in elite female and male runners and race walkers during a block of high intensity precompetition training Heikura, Ida A.
Dietary microperiodization in elite female and male runners and race walkers during a block of high intensity precompetition training. Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers Burke, Louise, Ross, Megan L.
Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers. Dynamic proteome profiling of individual proteins in human skeletal muscle after a high-fat diet and resistance exercise Camera, Donny M.
Dynamic proteome profiling of individual proteins in human skeletal muscle after a high-fat diet and resistance exercise. Transcriptomic and epigenetic responses to short-term nutrient-exercise stress in humans Laker, R.
Transcriptomic and epigenetic responses to short-term nutrient-exercise stress in humans. Scientific Reports. Commentaries on Viewpoint: A time for exercise: the exercise window Boule, Normand G. Commentaries on Viewpoint: A time for exercise: the exercise window.
Practical issues in evidence-based use of performance supplements: Supplement interactions, repeated use and individual responses Burke, Louise M.. Practical issues in evidence-based use of performance supplements: Supplement interactions, repeated use and individual responses.
S79 - S Communicating sports science in the age of the twittersphere Burke, Louise. Communicating sports science in the age of the twittersphere.
Sprinting toward fitness Gibala, M. Sprinting toward fitness. Expression of microRNAs and target proteins in skeletal muscle of rats selectively bred for high and low running capacity Pinto, Samuel K. Expression of microRNAs and target proteins in skeletal muscle of rats selectively bred for high and low running capacity.
American Journal of Physiology - Endocrinology and Metabolism. Weight regain: no link to success in a real-life multiday boxing tournament Reale, Reid, Cox, Gregory R. Weight regain: no link to success in a real-life multiday boxing tournament. Role of fluid intake in endurance sports Burke, Louise M..
Role of fluid intake in endurance sports. In In Meyer, Flavia, Szygula, Zbigniew and Wilk, Boguslaw Ed. Fluid balance, hydration, and athletic performance pp.
Postexercise high-fat feeding suppresses p70S6K1 activity in human skeletal muscle Hammond, Kelly M. Postexercise high-fat feeding suppresses p70S6K1 activity in human skeletal muscle. Adaptations to prolonged, intense endurance training in human skeletal muscle Hawley, J.
Adaptations to prolonged, intense endurance training in human skeletal muscle. In In I Mujika and Y Le Meur Ed. Endurance Training pp.
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To investigate the effect of caffeine ingestion Caffeien the 3-min Cwffeine test 3MT performance and plasma electrolytes in athletes. During Body comparison first visit, participants performed an incremental powdr test to determine their 3MT resistance. After a familiarization trial, participants performed a CAF or PL trial according to a randomized crossover design. One hour after ingesting capsules, the participants performed the 3MT to estimate the end-test power EP and work done above EP WEP. Significant differences in WEP CAF vs. PL, PL, ± 37 vs.
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A primary Caffejne of adenosine in the nervous system appears to be to inhibit the Caaffeine of various neurotransmitters, and possibly glutamate in Energy-efficient lighting, through Caffeibe receptors.
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Caffeine, by binding outout the ryanodine receptor, stimulates calcium fluxes annd can result in arrhythmias, which are linked to the Anx inotropic effect Czffeine caffeine. Another possibility anx inhibition of phosphodiesterases, which results in an increase in the intracellular concentration of cAMP and cGMP which under normal circumstances are degraded by phosphodiesterase The analysis of successive RR powwr the time elapsed between two lutput R-waves of the QRS signal on the electrocardiogramalso reported as heart rate variability Caffeinallows estimating the ouhput nervous ppower ANS activity through a non-invasive method Previous studies 15xnd investigated the impact poeer CAF on ANS Cafeine HRV, reporting HRV ojtput with Cafffine doses, while Caffwine strategies could increase the HRV.
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Although it is Metabolism boosting foods comparing and contrasting the Citrus oil for freshening indoor air, these inconsistent findings may be related to the dosage of caffeine ohtput.
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At the post-exercise assessment, in the Caffeibe condition, 7. In the PC condition, In outpht CC condition, Carfeine A post outpug analysis indicated that all studied HRV parameters changed significantly after the TT-test, without powwr between pre supplementation ane pre exercise outout Fig.
θ Post was significantly Caffekne from other Mexican coffee beans. Considering the caffeine supplementation comparisons, Bayesian analysis indicated moderate to anecdotal posterior probability favoring the null hypothesis, which was found for V0, V1 and V2.
The results from inferential and Opwer statistics are presented Hunger and urbanization Table 2. According Caffeie Bayes Factor analyzes for powef of TT-test execution, there is lutput posterior Cafgeine of These Bayes Factor indicated that the posterior probability favoring the alternative hypothesis were moderate and strong, respectively.
According to Bayes Factor analyzes for average power output, there is a posterior probability of These Bayes Factor indicated that the posterior probability favoring the alternative hypothesis were strong and very strong, respectively.
The results from inferential and Bayesian statistics are presented in Table 3. The parameter V0 was significantly greater in the condition PP when compared to other conditions.
The V0 exhibited a decline along the TT-test. The condition CC was significantly lower than PP condition at the midway of the exercise protocol.
It was observed a significantly increase along the TT-test Fig. The V2 was significantly greater in the condition CC when compared to other conditions.
Additionally, the V2 increased along the TT-test. At the condition PC, the V2 exhibited a significantly increase from midway to the final of exercise protocol.
At the final of exercise protocol, CC and PC exhibited greater V2 when compared to the condition PP Fig. According to Bayes Factor analyzes, there is a posterior probability of For V2, the Bayes Factor analyzes indicated a posterior probability The results from inferential and Bayesian statistics are presented in Table 4.
Since our study presented data from 1 procedures to ensure the control of experiments blood CAF quantification, HRV PRE suppl and POS exerc ; 2 performance in TT-test; 3 HRV along and after the TT-test, the discussion was structured to follow the exposed sequence. In our study, volunteers performed the TT-test under the same nutritional conditions, since the h dietary records did not show significant differences between the PP, PC, and CC conditions.
Additionally, the presence of foods, substances, supplements, or medicines containing CAF was also not detected in the records, since blood analysis by HPLC confirmed no serum CAF concentration in athletes at the baseline for PC and CC conditionsand after the supplementation, when submitted to placebo condition i.
As expected, at the conditions PC and CC, blood CAF concentration increased 1 h after supplementation Table 1. It is important to highlight that the use of analytical methods, as HPLC, to detect CAF in blood samples before and after supplementation is fundamental control method to ensure and validate the supplementation effects 27 and, in our study, was critical to ensure that volunteers performed the tests exclusively under the effect of experimental supplementation of CAF i.
Other adopted procedure to ensure the control of experiments was the recordings of successive RR intervals before and after supplementation, and our results indicated no differences among the CAF i. A recent study 28 investigated the influence of different caffeinated beverages energy drink, coffee, and cola on HRV parameters obtained through non-linear methods.
From a 5-min recording at sitting position, the authors identified that energy drink and coffee beverages could influence the HRV complexity parameters: Largest Lyapunov exponent and correlation dimensionsuggesting a greater variability of successive RR intervals, which have been associated to a better health status.
The use of non-linear methods to analyze the RR intervals variability has been reported as a more suitable tool to quantify complex phenomena such as control of cardiac function mediated by ANS 29 Results from pharmacological blockage 29 and during tilt test 29 found that the V0 pattern reflects sympathetic modulation, the V2 pattern parasympathetic modulation, and the V1 pattern reflects sympathovagal balance.
These results also confirm that the probability of harmful effects from acute CAF supplementation is anecdotal, which was confirmed by Bayesian analysis carried out in our study. It is important to note that the behavior of successive RR intervals is different at rest and along a high-intensity physical test, then, the significant differences in HRV parameters observed during the TT-test should be discussed apart from data obtained at supine position.
We found a significant acute performance improvement with CAF supplementation, independently of supplementation strategy i. PP to strong CC vs. PP posterior probability favoring the alternative hypothesis Table 3.
The ergogenic effect of CAF is widely demonstrated, especially in TT-tests 313233as we used. The present study also observed a better power output performance of athletes in the caffeine condition when compared to the placebo condition.
Curiously, the behavior of power output along the TT-test was clearly different between CAF supplementation PC or CC and placebo Fig. At CAF supplementation conditions the power output was higher since the beginning of TT-test, maintaining quasi-stable along all the exercise, while at placebo condition the power was increasing along the exercise.
The excitatory and alerting effects caused by CAF may explain the increased locomotor activity seen at the beginning of the test Mechanisms involving the effects of caffeine at the level of the central pattern generator of the lumbar spine network, enhancing the locomotor action, have been recently described 35facilitating limb activity through inhibition of A1 receptors and subsequent activation of dopamine receptors through an intracellular mechanism dependent on cAMP-dependent protein kinase.
This effect probably leads to a great ability to develop power output since the beginning of the exercise. Compared to tests with anaerobic predominance, as the Wingate test, the chosen TT-test spends a long time to be completed, making it infeasible to apply a maximal power output all time along the exercise.
It is expected that experienced cyclists learn to control the intensity to complete the TT-test, then it is interesting the divergent behavior between supplemented conditions and placebo, since at placebo conditions volunteers adjusted the power output along the exercise, while at CAF supplementation they maintained the power output along all TT-test, being higher than placebo at the beginning of TT-test.
In general, well-designed caffeine supplementation strategies can contribute to the improvement of countermovement jump CMJ height, average power, peak power, endurance muscle, and strength muscle Findings 37 support the hypothesis that the ergogenic effect of CAF would act in a dose-dependent manner.
Furthermore, they suggest that habitual consumption of products containing CAF would alter the CAF supplementation effect. Durkalec-Michalski et al. Thus, they suggested that athletes who habitually consume caffeine-containing products would need higher doses to promote specific performance improvement.
The ergogenic effects of caffeine depend on several mechanisms that can vary, such as time course, dose, and magnitude of dependence. Regular caffeine consumption positively induces the production of the Cytochrome P CYP1A2 enzyme group, increasing the rate of metabolism in regular users 5.
Therefore, different consumption strategies added to acute intake doses pre-test can produce distinct ergogenic effects. For example, Beaumont et al. This strategy impacts the ability to perform total work on the cycle ergometer, generating tolerance effects on endurance performance.
Furthermore, constant caffeine use also affected cycle ergometer sprint performance. Lara et al. They found that this strategy chronically caused a reduction in the magnitude of ergogenicity in the ventilatory response. However, it significantly increased peak power during a maximal incremental test during the first 15 days of ingestion.
They also found an improvement in VO 2 max in the first four days when compared to placebo treatment. Daily caffeine intake before exercise also produced a higher peak power for approximately 18 days after ingestion. After that period, the performance increases were not statistically different from placebo.
These results suggest the existence of progressive tolerance to the performance benefits of caffeine, as the ergogenic magnitude of caffeine was verified in the first days of ingestion for both endurance and muscle power exercises.
Thus, the time course of habituation is poorly understood and can be mainly affected by routine caffeine consumption. The impact of habituation probably can be modified by acute intake substantially greater than usual.
Concerns about caffeine consumption on cardiovascular activity during intense exercise are commonly related to dose, being reported that high-dose of caffeine intake can cause tachycardia, palpitations, and a rapid rise in blood pressure However, moderate caffeine intake does not adversely affect cardiovascular health 39despite moderate CAF consumption could affect contractility, myocardial conduction, vascular tone, and the sympathoadrenal system In this setting, the results of this study reinforce the possibility of increasing parasympathetic modulation after caffeine ingestion and add important information suggesting that the relationship between caffeine dosage and parasympathetic reactivity is not linear.
Sarshin et al. These data present robust evidence of an interesting clinical effect of CAF, diverging from the mainstream of harmful effect of CAF supplementation on cardiovascular health.
It is worthwhile to emphasize that 41 did not analyzed the RR interval variability along the exercise, leaving a lack of information about the safety of caffeine during intense exercise.
Our data obtained along the TT-test indicated a progressive increase of the parameter V2, achieving higher values at CAF supplementation PC and CCwhen compared to placebo. These find suggest a progressive increase of an indicator of parasympathetic activity The pattern variation of successive RR intervals, evaluated by symbolic analysis along the TT-test revealed that the sympathetic modulation V0 had similar behavior between the conditions PP, CP, and CC at the beginning and midway of the exercise, being more pronounced at the beginning of the test, as expected, owing to the high sympathetic drive at the beginning of exercises.
: Caffeine and power output| Caffeine increases motor output entropy and performance in 4 km cycling time trial | PLOS ONE | IOC Consensus Statement: Dietary Supplements and the High-Performance Caffeine and power output. Article Cafteine PubMed Central Fatigue and exercise performance Scholar. Outpuh, Caffeine and power output. Metabolic adaptations to training. Those with the CC genotype of ADORA2A rs consistently performed on a higher level on the sustained vigilant attention task than T-allele -carriers; however, this was tested in ADORA2A haplotypes that included combinations of 8 SNPs. Muscle Nerve. |
| How Caffeine Improves Exercise Performance | Athletes may also want to familiarise themselves with caffeine consumption during training and find the consumption protocol which provides the best possible effects for their own individual needs. Caffeine, Coffee, and Health. Under similar conditions of sleep deprivation, Tikuisis et al. Acute Specific Effects of Caffeine-containing Energy Drink on Different Physical Performances in Resistance-trained Men. Schwabe, U. |
| Caffeine ingestion improves power output decrement during 3-min all-out exercise | Furthermore, due to the high degree of inter-individual variability of effects [ 42 ], these results should be interpreted with caution when it comes to prescribing caffeine supplementation to individuals. These side effects may be enhanced in naive caffeine users [ 3 , 5 ], so extra precaution may be warranted in such individuals. Caffeine appears to provide significant ergogenic effects on muscle strength and power. The expression of strength in the form of 1RM is most specific to the sport of powerlifting but may translate to performance improvements in a variety of other strength-power sports. The effects of caffeine on muscle power may apply to athletes in a variety of sports in which jumping is a predominant activity that affects the sport-specific performance. 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Strossmayer University, Osijek, Croatia. You can also search for this author in PubMed Google Scholar. JG and ZP conceived the idea and conceptualized the review. JG and BL conducted the study selection, data extraction, and methodological quality assessment. JG conducted the meta-analysis. JG drafted the initial manuscript. JG, ET, BL, and ZP contributed to writing the manuscript. All authors read and approved the final manuscript. Correspondence to Zeljko Pedisic. Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Open Access This article is distributed under the terms of the Creative Commons Attribution 4. Reprints and permissions. Grgic, J. et al. Effects of caffeine intake on muscle strength and power: a systematic review and meta-analysis. J Int Soc Sports Nutr 15 , 11 Download citation. Received : 19 July Accepted : 27 February Published : 05 March Anyone you share the following link with will be able to read this content:. Sorry, a shareable link is not currently available for this article. Provided by the Springer Nature SharedIt content-sharing initiative. Skip to main content. Search all BMC articles Search. Download PDF. Download ePub. Review Open access Published: 05 March Effects of caffeine intake on muscle strength and power: a systematic review and meta-analysis Jozo Grgic 1 , Eric T. Abstract Background Caffeine is commonly used as an ergogenic aid. Methods A search through eight databases was performed to find studies on the effects of caffeine on: i maximal muscle strength measured using 1 repetition maximum tests; and ii muscle power assessed by tests of vertical jump. Results Ten studies on the strength outcome and ten studies on the power outcome met the inclusion criteria for the meta-analyses. Conclusion The meta-analyses showed significant ergogenic effects of caffeine ingestion on maximal muscle strength of upper body and muscle power. Methods Search strategy The systematic literature search was performed following the PRISMA guidelines [ 17 ]. Methodological quality The point PEDro scale was used for the assessment of the methodological quality of studies [ 18 ]. Statistical analysis The meta-analysis was performed using the Comprehensive Meta-analysis software, version 2 Biostat Inc. Results The literature search yielded a total of documents. Table 1 Studies included in the analysis: summary of study designs Full size table. Flow diagram of the search and study selection process. Full size image. Table 2 Results from the subgroup meta-analyses Full size table. Discussion The results of the meta-analysis show that caffeine may be an effective ergogenic aid for muscle strength and power. Strength outcomes Upper and lower body strength The subgroup analysis indicated a significant increase in upper body, but not lower body strength, with caffeine ingestion. Sex The subgroup analysis in males showed a significant improvement in strength with caffeine ingestion. Caffeine form The subgroup analysis indicated significant increases in strength after the ingestion of caffeine in the capsule form. Power outcomes The meta-analysis supports caffeine as an effective ergogenic aid for achieving acute increases in muscle power expressed as vertical jump height. Methodological quality The PEDro scale showed good to excellent quality among the included studies, suggesting that the results of the current meta-analysis were not confounded by the inclusion of studies with poor research methodology. Conclusion Caffeine appears to provide significant ergogenic effects on muscle strength and power. References Rivers WHR, Webber HN. Mechanisms involving the effects of caffeine at the level of the central pattern generator of the lumbar spine network, enhancing the locomotor action, have been recently described 35 , facilitating limb activity through inhibition of A1 receptors and subsequent activation of dopamine receptors through an intracellular mechanism dependent on cAMP-dependent protein kinase. This effect probably leads to a great ability to develop power output since the beginning of the exercise. Compared to tests with anaerobic predominance, as the Wingate test, the chosen TT-test spends a long time to be completed, making it infeasible to apply a maximal power output all time along the exercise. It is expected that experienced cyclists learn to control the intensity to complete the TT-test, then it is interesting the divergent behavior between supplemented conditions and placebo, since at placebo conditions volunteers adjusted the power output along the exercise, while at CAF supplementation they maintained the power output along all TT-test, being higher than placebo at the beginning of TT-test. In general, well-designed caffeine supplementation strategies can contribute to the improvement of countermovement jump CMJ height, average power, peak power, endurance muscle, and strength muscle Findings 37 support the hypothesis that the ergogenic effect of CAF would act in a dose-dependent manner. Furthermore, they suggest that habitual consumption of products containing CAF would alter the CAF supplementation effect. Durkalec-Michalski et al. Thus, they suggested that athletes who habitually consume caffeine-containing products would need higher doses to promote specific performance improvement. The ergogenic effects of caffeine depend on several mechanisms that can vary, such as time course, dose, and magnitude of dependence. Regular caffeine consumption positively induces the production of the Cytochrome P CYP1A2 enzyme group, increasing the rate of metabolism in regular users 5. Therefore, different consumption strategies added to acute intake doses pre-test can produce distinct ergogenic effects. For example, Beaumont et al. This strategy impacts the ability to perform total work on the cycle ergometer, generating tolerance effects on endurance performance. Furthermore, constant caffeine use also affected cycle ergometer sprint performance. Lara et al. They found that this strategy chronically caused a reduction in the magnitude of ergogenicity in the ventilatory response. However, it significantly increased peak power during a maximal incremental test during the first 15 days of ingestion. They also found an improvement in VO 2 max in the first four days when compared to placebo treatment. Daily caffeine intake before exercise also produced a higher peak power for approximately 18 days after ingestion. After that period, the performance increases were not statistically different from placebo. These results suggest the existence of progressive tolerance to the performance benefits of caffeine, as the ergogenic magnitude of caffeine was verified in the first days of ingestion for both endurance and muscle power exercises. Thus, the time course of habituation is poorly understood and can be mainly affected by routine caffeine consumption. The impact of habituation probably can be modified by acute intake substantially greater than usual. Concerns about caffeine consumption on cardiovascular activity during intense exercise are commonly related to dose, being reported that high-dose of caffeine intake can cause tachycardia, palpitations, and a rapid rise in blood pressure However, moderate caffeine intake does not adversely affect cardiovascular health 39 , despite moderate CAF consumption could affect contractility, myocardial conduction, vascular tone, and the sympathoadrenal system In this setting, the results of this study reinforce the possibility of increasing parasympathetic modulation after caffeine ingestion and add important information suggesting that the relationship between caffeine dosage and parasympathetic reactivity is not linear. Sarshin et al. These data present robust evidence of an interesting clinical effect of CAF, diverging from the mainstream of harmful effect of CAF supplementation on cardiovascular health. It is worthwhile to emphasize that 41 did not analyzed the RR interval variability along the exercise, leaving a lack of information about the safety of caffeine during intense exercise. Our data obtained along the TT-test indicated a progressive increase of the parameter V2, achieving higher values at CAF supplementation PC and CC , when compared to placebo. These find suggest a progressive increase of an indicator of parasympathetic activity The pattern variation of successive RR intervals, evaluated by symbolic analysis along the TT-test revealed that the sympathetic modulation V0 had similar behavior between the conditions PP, CP, and CC at the beginning and midway of the exercise, being more pronounced at the beginning of the test, as expected, owing to the high sympathetic drive at the beginning of exercises. The V0 exhibited a decline along with the exercise, which could be related to expected cardiovascular adjusts along the submaximal long exercise. At the final of TT-test, we found an interesting behavior with smaller V0, a marker of sympathetic modulation, at CAF conditions PC and CC when compared to placebo. The parameter V1 pattern reflecting sympathovagal balance exhibited an increase along the exercise, with similar behavior among the conditions. The parameter V2 pattern reflecting parasympathetic modulation increased along the TT-test similarly among supplementation conditions PP, PC, and CC at the beginning and midway of the exercise. However, at the final, a prominent parasympathetic modulation was observed in the CAF conditions PC and CC compared to the placebo. These results could reflect a protective effect of CAF during the used TT-test since the sympathetic drive was not the greater in CAF conditions at the beginning of the activity, despite a higher power output at this moment. Autonomic control during physical exercise under CAF conditions can be modified; the baroreflex is attenuated at the brainstem level due to activation of the metaboreflex. Increased metabolic accumulation i. As a consequence, stimulation of non-myelinated afferent fibers III and IV leads to sympathetic activity, inducing a more accentuated parasympathetic response due to the maintenance of output power for a longer time during exercise Similar responses were observed by Bunsawat et al. The authors 42 observed a parasympathetic response with the ingestion of mg of caffeine capsules compared to the placebo condition, resulting in greater exercise performance. Divergently from CAF conditions PC and CC , the placebo condition demanded more power output to complete the exercise at an expected time i. In line with this hypothesis, a parasympathetic withdrawal will be expected at the placebo condition, as we found. This suggests that the rapid onset of the sympathetic response in the final phase i. They suggested that effective cardioprotection strategies should increase cardiac parasympathetic activity, thus conferring plausible efficiency in reducing myocardial damage and decreasing myocardial morbidity and mortality Notwithstanding, it is important to note that the posterior probability of greater V2 and smaller V0 along TT-test with CAF supplementation were moderate to very-strong, as found with Bayesian inference Table 4. Clark et al. However, three methodological aspects need to be emphasized when comparing the results from this study 45 and ours. They used 1 a low dose of CAF an energy drink formula containing mg of caffeine ; 2 a graded exercise test to exhaustion; 3 a linear method to obtain estimations of heart autonomic modulation. A significant parasympathetic withdrawal is expected in exercise designed to increase the intensity in a predetermined manner until failure, and the lower CAF dose could be not sufficient to sustain the parasympathetic modulation along the exercise. Our study used an exercise mimetizing a competition, where the athlete could choose the intensity, but be aware of the aim of the exercise i. The last relevant difference between 45 and our study was the chosen method to analyze the variability of successive RR intervals, and nonlinear methods, as we used, is reported to be more suitable to quantify complex phenomena such as control of cardiac function mediated by ANS 46 , 47 , Despite the great effort to control the variables involved in the study, some limitations should be considered. One of the limitations of our findings is associated with the use of a cycle ergometer in the laboratory. Thus, the findings of the present study should be confirmed in additional research protocols, which use field tests i. Other limitations of the present study are related to the analysis of the plasma catecholamine concentrations and the sympathetic nerve activity; however, we used HRV, a simple non-invasive method and one of the most promising quantitative markers of autonomic heart rate balance The urine content of caffeine metabolites paraxanthine, theobromine, and theophylline was also not analyzed in the present study, which could indirectly reflect the pharmacokinetics of CAF. It has been shown that the increase in the concentration of paraxanthine one of the metabolites of CAF has a different relationship with plasma levels of CAF after the min period of CAF ingestion time used in the present study The increase in paraxanthine occurs at a slower rate than the CAF in plasma during this period 60 min , making its detection in urine even more difficult Finally, we do not control Cytochrome P CYP1A2 polymorphisms. These variations in genes encoding CYP1A2 proteins can impact caffeine metabolism and potentiate dopaminergic neurotransmission. However, as this condition is uncommon, conducting a study with this genetic outcome requires a robust number of participants As a novelty from our study we highlight the use of a 16 km TT-test, a long task that mimetize cycling competitions tasks, instead of predominantly anaerobic tests, which have been used in previous studies, investigating the cardiovascular effects of CAF supplementation. The use of symbolic analysis to estimate sympathovagal modulation, and the Bayesian inference as a statistical approach, also represent novelty, since previous studies in the field of our study did not include these promising mathematical approaches. It is noteworthy that the cardioprotective effect of caffeine was observed in healthy volunteers, and our findings should not be transmitted to patients at high cardiovascular risk or cardiovascular disease. Other studies must be carried out to assess the effects of different doses of CAF, and establish the most accurate dosage that enhances the results, favors cardioprotection, and minimizes risks. Assuming repeated measures, within factors three interventions. The inclusion criteria were: all had at least 4 years of experience, participated in at least 20 competitions in and , have no history of cardiorespiratory, gastrointestinal, and musculoskeletal disorders in the last 3 months. A simple questionnaire evaluated the training volume of all participants to warrant a homogenous sample for the study. In addition, a validated caffeine consumption questionnaire was administered to the participants, showing that all participants were moderate to high caffeine consumers The research protocol 2. A randomized, double-blind, crossover, placebo-controlled design was used in this study. On the first visit to the laboratory, participants underwent dietary assessment and cycling test to exhaustion. On the second visit, cyclists became familiar with the time trial test. So they received four visits from the researchers at home, one per day, for delivery and verification of capsule consumption according to randomization. The other day they consumed the capsule acutely 60 min before the 16 km time trial test. The study preconized a seven-day washout between the different intervention strategies 19 , 20 , 21 , We tested the following strategies: Placebo—Placebo PP , participants received Placebo 4-day supplementation , and Placebo acute ingestion, 60 min before simulated cycling TT-test completed. Placebo capsules were mg of magnesium silicate single daily dose. Placebo—Caffeine PC , participants received Placebo 4-day supplementation , and Caffeine acute ingestion, 60 min before simulated cycling TT-test completed. Caffeine—Caffeine CC , participants received Caffeine 4-day supplementation , and Caffeine acute ingestion, 60 min before simulated cycling TT-test completed. At the first visit to the laboratory, the researchers verified the routine energy and caffeine intake of food, VO 2 max, and workload capacity in the graded test until exhaustion in the cycle ergometer. The athletes were instructed to withdraw all their caffeine consumption i. On the test day, cyclists arrived fasting in the laboratory, and soon an intravenous cannula 20G Jelco; B. Braun Medical Inc. Cyclists did not exercise 24 h before the experimental trials in the laboratory. The athletes were instructed to continue the routine of daily training. The experimental trials were performed at the same time of day a. com Supplementary File -Disposition of study participants. To determine the VO 2 max, participants performed a graded exercise test to exhaustion on the cycle ergometer Cefise, São Paulo, Brazil. Heart rate was monitored continuously Polar Electro Oy, Kempele, Finland. The pulmonary gas exchange was determined breath by breath for carbon dioxide, oxygen concentrations, and minute ventilation using a VO gas analysis system MedGraphics, St. Paul, MN, USA. The equipment was automatically calibrated according to the manufacturer's specifications before each test. The present study determined and validated the VO 2 max following these criteria: increase in VO 2 less than 2. Because the participants are used to consuming average amounts of caffeine daily, around In the presence of a researcher, all athletes were instructed to take a single capsule daily at the same time a. during the 4-day supplementation. In acute ingestion, the capsule was administered with mL of water before simulated cycling TT-test completed. Supplements for each participant were prepared and separated by a non-affiliated researcher to ensure double-blinding. With this information, we would know the percentage of belief of caffeine consumption. A high frequency of this belief could influence the study results as described by other authors Cyclists were instructed to maintain their dietary and hydration patterns. A h dietary record was completed by each athlete on the first visit and, before the first test, it was photocopied and returned to the athletes so that the same diet could be repeated for subsequent trials. The energy intake, carbohydrates, total proteins, and total lipids was determined. The TACO database was used to quantify macronutrient intake and the Dietpro 5i software version 5. To assess the dietary frequency and the amount of caffeine, a validated questionnaire was applied by trained nutritionists. The questionnaire consists of a list of dietary sources of CAF coffee, tea, cocoa, chocolate, soft drinks, medicines, and dietary supplements and the time of consumption. Household measures were used to assess the amount of food consumed according to the following frequency of consumption Types of foods, dietary supplements, and medications that contained caffeine were identified. The CAF content was obtained from the U. Successive RR intervals were acquired for 5 min while supine REST and along the TT-test. Beat-to-beat intervals were recorded by a validated heart rate monitor Polar RS, Polar Electro Oy, Kempele, Finland for HRV analysis The sampling frequency was set at Hz, the smoothness prior method with alpha set at was used for detrended the R-R intervals series. They were studied 48 h far away from the last bout of physical exercise to avoid the short-term autonomic and cardiovascular confounding after-effects induced by recent training sessions. Recordings at supine position HRV-SP were performed three times, before the ingestion of the capsule PRE suppl , 60 min after supplementation PRE exerc , and 10 min after the TT-test POST. Recording of the HRV during the TT-test HRV-TT was done during the entire time of the exercise execution. The nonlinear dynamics of successive RR intervals were assessed by symbolic analysis 29 during the TT-test. The R-R dynamics were classified into three pattern families: I patterns with no variation V0; all three symbols were equal ; II patterns with one variation V1; two consequent symbols were equal, and the remaining symbol was different ; and III patterns with two unlike or like variations V2; all of the symbols were different from the previous ones. The percentage of the patterns V0 was calculated as sympathetic modulation predominance, V1 reflects sympathetic and parasympathetic modulation, and the V2 calculated as a parasympathetic modulation as suggested by Santos et al. The data i. For the recordings from supine position, the 5-min successive RR intervals were selected for analysis, while for TT-test, the visual inspection was carried out to find and select a segment of successive RR intervals where the stationarity of the time series was acceptable at three moments: beginning, midway and final of each TT-test session. All RR interval variability analyses were carried out by the same researcher which was blind for the applied treatment in each data set. The measurement of blood levels of caffeine was performed at baseline and 60 min after intake of capsules. Serum was obtained by centrifugation at 2. The caffeine blood levels were determined using a HPLC method previously described The HPLC analyses were carried out using a Shimadzu chromatograph Shimadzu Corp. Participants did not receive any performance feedback during the tests. The only information that the participants received was the distance reached: 2 km, 4 km, 6 km, 8 km, 10 km, 12 km, 14 km, and 16 km. The analyses of the power outputs were measured in 3 equals intervals Beginning, Midway and Final of the completed TT-test time curve. The dynamics of data acquisition in the laboratory can be seen in Fig. Dynamics of data acquisition. Placebo—Placebo PP , Placebo—Caffeine PC and Caffeine—Caffeine CC conditions were tested in 16 km time Trial 16 km TT performance and HRV analysis were done pre supplementation HRV-SP PRE suppl , post supplementation HRV-SP POST suppl during 16 km TT HRV-TT and post 16 km TT HRV-SP Post. When data showed normal distribution the variables were analyzed by mixed ANOVA with repeated measures. The Mauchly sphericity test was performed for all tested variables, and the Greenhouse—Geisser correction was used in cases where the sphericity assumption was violated. Tukey's post hoc test was used for means multiple comparisons. When data presented a non-normal distribution the Kruskal Wallis test was used version To check the qualitative outcomes and the probability to replicate the same results i. The posterior odds have been corrected for multiple testing by fixing to 0. The "U" in the Bayes factor denotes that it is uncorrected. We made all BF analysis through the JAMOVI. Mitchell, D. Beverage caffeine intakes in the U. Food Chem. Article CAS PubMed Google Scholar. Southward, K. The effect of acute caffeine ingestion on endurance performance: A systematic review and meta-analysis. Sports Med. Article PubMed Google Scholar. Ferreira, R. et al. Effects of caffeine supplementation on physical performance of soccer players: Systematic review and meta-analysis. Sports Health 13 , — Lara, B. Time course of tolerance to the performance benefits of caffeine. PLoS ONE 14 , e Article CAS PubMed PubMed Central Google Scholar. Pickering, C. What should we do about habitual caffeine use in athletes?. Zuchinali, P. Short-term effects of high-dose caffeine on cardiac arrhythmias in patients with heart failure: A randomized clinical trial. JAMA Intern. Kitano, T. Suicidal attempt with caffeine overdose treated with dexmedetomidine: A case report. Case Rep. Article PubMed PubMed Central Google Scholar. Elhaj, H. Perceived consumption of a high-dose caffeine drink delays neuromuscular fatigue. Strength Cond. Publish Ahead of Print Schwabe, U. Xanthine derivatives as antagonists at A1 and A2 adenosine receptors. Petzer, A. The interactions of caffeine with monoamine oxidase. Life Sci. Lévy, S. European Cardiac Arrhythmia Society Statement on the cardiovascular events associated with the use or abuse of energy drinks. Basrai, M. Energy drinks induce acute cardiovascular and metabolic changes pointing to potential risks for young adults: A randomized controlled trial. Okudaira, N. A knock-in mouse model of N-terminal RW mutation of cardiac ryanodine receptor exhibits arrhythmogenesis with abnormal calcium dynamics in cardiomyocytes. Malik, M. Heart rate variability: Standards of measurement, physiological interpretation, and clinical use. Heart J. Article Google Scholar. Dömötör, Z. Subjective and objective effects of coffee consumption—Caffeine or expectations?. Acta Physiol. Sondermeijer, H. Acute effects of caffeine on heart rate variability. dos Santos, J. The D allele of angiotensin-converting enzyme gene is associated with a worse autonomic heart control in community-based older adults. Kim, J. Nutritional strategies to optimize performance and recovery in rowing athletes. Nutrients 12 , Article CAS PubMed Central Google Scholar. Wilk, M. The acute effects of caffeine intake on time under tension and power generated during the bench press movement. Sports Nutr. Ribeiro, B. Caffeine attenuates decreases in leg power without increased muscle damage. Irwin, C. Caffeine withdrawal and high-intensity endurance cycling performance. Sports Sci. Beaumont, R. Chronic ingestion of a low dose of caffeine induces tolerance to the performance benefits of caffeine. Martins, G. Caffeine and exercise performance: Possible directions for definitive findings. Front Sports Act Living 2 , Dodd, S. The effects of caffeine on graded exercise performance in caffeine naive versus habituated subjects. Gonzaga, L. Caffeine affects autonomic control of heart rate and blood pressure recovery after aerobic exercise in young adults: A crossover study. Article ADS PubMed PubMed Central Google Scholar. Lahiri, M. Recovery of heart rate variability and ventricular repolarization indices following exercise. Noninvasive Electrocardiol. Reserch, C. Comparison of plasma caffeine concentration after oral consumption of caffeinated beverages with varied Bioactive compounds in healthy volunteers. Case Med. Caliskan, S. Non-linear analysis of heart rate variability for evaluating the acute effects of caffeinated beverages in young adults—ERRATUM. Young 30 , Guzzetti, S. Symbolic dynamics of heart rate variability: A probe to investigate cardiac autonomic modulation. Circulation , — Porta, A. Assessment of cardiac autonomic modulation during graded head-up tilt by symbolic analysis of heart rate variability. Heart Circ. Glaister, M. Effects of caffeine on time trial performance and associated physiological responses: A meta-analysis. Caffeine Adenosine Res. Article CAS Google Scholar. Shen, J. Establishing a relationship between the effect of caffeine and duration of endurance athletic time trial events: A systematic review and meta-analysis. Sport 22 , — Ivy, J. Improved cycling time-trial performance after ingestion of a caffeine energy drink. Sport Nutr. Article MathSciNet CAS PubMed Google Scholar. Khcharem, A. Acute caffeine ingestion improves 3-km run performance, cognitive function, and psychological state of young recreational runners. Acevedo, J. Caffeine stimulates locomotor activity in the mammalian spinal cord via adenosine A1 receptor-dopamine D1 receptor interaction and PKA-dependent mechanisms. Neuropharmacology , — Lago-RodrÍguez, Á. Caffeine improves performance but not duration of the countermovement jump phases. Fitness 61 , — Durkalec-Michalski, K. Dose-dependent effect of caffeine supplementation on judo-specific performance and training activity: A randomized placebo-controlled crossover trial. De Sanctis, V. Caffeinated energy drink consumption among adolescents and potential health consequences associated with their use: A significant public health hazard. Acta Biomed. PubMed PubMed Central Google Scholar. Smith, B. Caffeine and activation theory: effects on health and behavior CRC Press, Boca Raton, Book Google Scholar. Riksen, N. The cardiovascular effects of methylxanthines. |
Caffeine and power output -
Notwithstanding, lack of pattern of supplementation approach, including dose and selected strategy, also contribute to divergence in the issue of this study. Different CAF dietary strategies are used to enhance performance On the other hand, despite the findings of studies 22 , 23 , 24 that indicate tolerance to ergogenic effects with the regular use of CAF, other authors 4 , 5 recommend the use of doses that represent an average amount of caffeine above the usual i.
Although it is difficult comparing and contrasting the results, these inconsistent findings may be related to the dosage of caffeine used. However, the use of these strategies can cause a high risk of adverse effects 4 , 5 , such as changes in autonomic modulation, which can promote an enabling environment for the development of rhythm disturbances and abnormal responses of heart rate The present study was designed to investigate, in cyclists, the effects of different CAF dietary strategies to compare the impact on athletic performance and cardiac autonomic response.
At the post-exercise assessment, in the PP condition, 7. In the PC condition, In the CC condition, A post hoc analysis indicated that all studied HRV parameters changed significantly after the TT-test, without differences between pre supplementation and pre exercise measures Fig.
θ Post was significantly different from other moments. Considering the caffeine supplementation comparisons, Bayesian analysis indicated moderate to anecdotal posterior probability favoring the null hypothesis, which was found for V0, V1 and V2.
The results from inferential and Bayesian statistics are presented in Table 2. According to Bayes Factor analyzes for time of TT-test execution, there is a posterior probability of These Bayes Factor indicated that the posterior probability favoring the alternative hypothesis were moderate and strong, respectively.
According to Bayes Factor analyzes for average power output, there is a posterior probability of These Bayes Factor indicated that the posterior probability favoring the alternative hypothesis were strong and very strong, respectively.
The results from inferential and Bayesian statistics are presented in Table 3. The parameter V0 was significantly greater in the condition PP when compared to other conditions. The V0 exhibited a decline along the TT-test.
The condition CC was significantly lower than PP condition at the midway of the exercise protocol. It was observed a significantly increase along the TT-test Fig.
The V2 was significantly greater in the condition CC when compared to other conditions. Additionally, the V2 increased along the TT-test. At the condition PC, the V2 exhibited a significantly increase from midway to the final of exercise protocol.
At the final of exercise protocol, CC and PC exhibited greater V2 when compared to the condition PP Fig. According to Bayes Factor analyzes, there is a posterior probability of For V2, the Bayes Factor analyzes indicated a posterior probability The results from inferential and Bayesian statistics are presented in Table 4.
Since our study presented data from 1 procedures to ensure the control of experiments blood CAF quantification, HRV PRE suppl and POS exerc ; 2 performance in TT-test; 3 HRV along and after the TT-test, the discussion was structured to follow the exposed sequence.
In our study, volunteers performed the TT-test under the same nutritional conditions, since the h dietary records did not show significant differences between the PP, PC, and CC conditions. Additionally, the presence of foods, substances, supplements, or medicines containing CAF was also not detected in the records, since blood analysis by HPLC confirmed no serum CAF concentration in athletes at the baseline for PC and CC conditions , and after the supplementation, when submitted to placebo condition i.
As expected, at the conditions PC and CC, blood CAF concentration increased 1 h after supplementation Table 1. It is important to highlight that the use of analytical methods, as HPLC, to detect CAF in blood samples before and after supplementation is fundamental control method to ensure and validate the supplementation effects 27 and, in our study, was critical to ensure that volunteers performed the tests exclusively under the effect of experimental supplementation of CAF i.
Other adopted procedure to ensure the control of experiments was the recordings of successive RR intervals before and after supplementation, and our results indicated no differences among the CAF i. A recent study 28 investigated the influence of different caffeinated beverages energy drink, coffee, and cola on HRV parameters obtained through non-linear methods.
From a 5-min recording at sitting position, the authors identified that energy drink and coffee beverages could influence the HRV complexity parameters: Largest Lyapunov exponent and correlation dimension , suggesting a greater variability of successive RR intervals, which have been associated to a better health status.
The use of non-linear methods to analyze the RR intervals variability has been reported as a more suitable tool to quantify complex phenomena such as control of cardiac function mediated by ANS 29 , Results from pharmacological blockage 29 and during tilt test 29 found that the V0 pattern reflects sympathetic modulation, the V2 pattern parasympathetic modulation, and the V1 pattern reflects sympathovagal balance.
These results also confirm that the probability of harmful effects from acute CAF supplementation is anecdotal, which was confirmed by Bayesian analysis carried out in our study.
It is important to note that the behavior of successive RR intervals is different at rest and along a high-intensity physical test, then, the significant differences in HRV parameters observed during the TT-test should be discussed apart from data obtained at supine position.
We found a significant acute performance improvement with CAF supplementation, independently of supplementation strategy i. PP to strong CC vs.
PP posterior probability favoring the alternative hypothesis Table 3. The ergogenic effect of CAF is widely demonstrated, especially in TT-tests 31 , 32 , 33 , as we used. The present study also observed a better power output performance of athletes in the caffeine condition when compared to the placebo condition.
Curiously, the behavior of power output along the TT-test was clearly different between CAF supplementation PC or CC and placebo Fig. At CAF supplementation conditions the power output was higher since the beginning of TT-test, maintaining quasi-stable along all the exercise, while at placebo condition the power was increasing along the exercise.
The excitatory and alerting effects caused by CAF may explain the increased locomotor activity seen at the beginning of the test Mechanisms involving the effects of caffeine at the level of the central pattern generator of the lumbar spine network, enhancing the locomotor action, have been recently described 35 , facilitating limb activity through inhibition of A1 receptors and subsequent activation of dopamine receptors through an intracellular mechanism dependent on cAMP-dependent protein kinase.
This effect probably leads to a great ability to develop power output since the beginning of the exercise. Compared to tests with anaerobic predominance, as the Wingate test, the chosen TT-test spends a long time to be completed, making it infeasible to apply a maximal power output all time along the exercise.
It is expected that experienced cyclists learn to control the intensity to complete the TT-test, then it is interesting the divergent behavior between supplemented conditions and placebo, since at placebo conditions volunteers adjusted the power output along the exercise, while at CAF supplementation they maintained the power output along all TT-test, being higher than placebo at the beginning of TT-test.
In general, well-designed caffeine supplementation strategies can contribute to the improvement of countermovement jump CMJ height, average power, peak power, endurance muscle, and strength muscle Findings 37 support the hypothesis that the ergogenic effect of CAF would act in a dose-dependent manner.
Furthermore, they suggest that habitual consumption of products containing CAF would alter the CAF supplementation effect. Durkalec-Michalski et al. Thus, they suggested that athletes who habitually consume caffeine-containing products would need higher doses to promote specific performance improvement.
The ergogenic effects of caffeine depend on several mechanisms that can vary, such as time course, dose, and magnitude of dependence. Regular caffeine consumption positively induces the production of the Cytochrome P CYP1A2 enzyme group, increasing the rate of metabolism in regular users 5.
Therefore, different consumption strategies added to acute intake doses pre-test can produce distinct ergogenic effects.
For example, Beaumont et al. This strategy impacts the ability to perform total work on the cycle ergometer, generating tolerance effects on endurance performance.
Furthermore, constant caffeine use also affected cycle ergometer sprint performance. Lara et al. They found that this strategy chronically caused a reduction in the magnitude of ergogenicity in the ventilatory response.
However, it significantly increased peak power during a maximal incremental test during the first 15 days of ingestion. They also found an improvement in VO 2 max in the first four days when compared to placebo treatment.
Daily caffeine intake before exercise also produced a higher peak power for approximately 18 days after ingestion. After that period, the performance increases were not statistically different from placebo.
These results suggest the existence of progressive tolerance to the performance benefits of caffeine, as the ergogenic magnitude of caffeine was verified in the first days of ingestion for both endurance and muscle power exercises.
Thus, the time course of habituation is poorly understood and can be mainly affected by routine caffeine consumption. The impact of habituation probably can be modified by acute intake substantially greater than usual. Concerns about caffeine consumption on cardiovascular activity during intense exercise are commonly related to dose, being reported that high-dose of caffeine intake can cause tachycardia, palpitations, and a rapid rise in blood pressure However, moderate caffeine intake does not adversely affect cardiovascular health 39 , despite moderate CAF consumption could affect contractility, myocardial conduction, vascular tone, and the sympathoadrenal system In this setting, the results of this study reinforce the possibility of increasing parasympathetic modulation after caffeine ingestion and add important information suggesting that the relationship between caffeine dosage and parasympathetic reactivity is not linear.
Sarshin et al. These data present robust evidence of an interesting clinical effect of CAF, diverging from the mainstream of harmful effect of CAF supplementation on cardiovascular health.
It is worthwhile to emphasize that 41 did not analyzed the RR interval variability along the exercise, leaving a lack of information about the safety of caffeine during intense exercise. Our data obtained along the TT-test indicated a progressive increase of the parameter V2, achieving higher values at CAF supplementation PC and CC , when compared to placebo.
These find suggest a progressive increase of an indicator of parasympathetic activity The pattern variation of successive RR intervals, evaluated by symbolic analysis along the TT-test revealed that the sympathetic modulation V0 had similar behavior between the conditions PP, CP, and CC at the beginning and midway of the exercise, being more pronounced at the beginning of the test, as expected, owing to the high sympathetic drive at the beginning of exercises.
The V0 exhibited a decline along with the exercise, which could be related to expected cardiovascular adjusts along the submaximal long exercise. At the final of TT-test, we found an interesting behavior with smaller V0, a marker of sympathetic modulation, at CAF conditions PC and CC when compared to placebo.
The parameter V1 pattern reflecting sympathovagal balance exhibited an increase along the exercise, with similar behavior among the conditions. The parameter V2 pattern reflecting parasympathetic modulation increased along the TT-test similarly among supplementation conditions PP, PC, and CC at the beginning and midway of the exercise.
However, at the final, a prominent parasympathetic modulation was observed in the CAF conditions PC and CC compared to the placebo.
These results could reflect a protective effect of CAF during the used TT-test since the sympathetic drive was not the greater in CAF conditions at the beginning of the activity, despite a higher power output at this moment.
Autonomic control during physical exercise under CAF conditions can be modified; the baroreflex is attenuated at the brainstem level due to activation of the metaboreflex. Increased metabolic accumulation i. As a consequence, stimulation of non-myelinated afferent fibers III and IV leads to sympathetic activity, inducing a more accentuated parasympathetic response due to the maintenance of output power for a longer time during exercise Similar responses were observed by Bunsawat et al.
The authors 42 observed a parasympathetic response with the ingestion of mg of caffeine capsules compared to the placebo condition, resulting in greater exercise performance.
Divergently from CAF conditions PC and CC , the placebo condition demanded more power output to complete the exercise at an expected time i. In line with this hypothesis, a parasympathetic withdrawal will be expected at the placebo condition, as we found.
This suggests that the rapid onset of the sympathetic response in the final phase i. They suggested that effective cardioprotection strategies should increase cardiac parasympathetic activity, thus conferring plausible efficiency in reducing myocardial damage and decreasing myocardial morbidity and mortality Notwithstanding, it is important to note that the posterior probability of greater V2 and smaller V0 along TT-test with CAF supplementation were moderate to very-strong, as found with Bayesian inference Table 4.
Clark et al. However, three methodological aspects need to be emphasized when comparing the results from this study 45 and ours.
They used 1 a low dose of CAF an energy drink formula containing mg of caffeine ; 2 a graded exercise test to exhaustion; 3 a linear method to obtain estimations of heart autonomic modulation.
A significant parasympathetic withdrawal is expected in exercise designed to increase the intensity in a predetermined manner until failure, and the lower CAF dose could be not sufficient to sustain the parasympathetic modulation along the exercise. Our study used an exercise mimetizing a competition, where the athlete could choose the intensity, but be aware of the aim of the exercise i.
The last relevant difference between 45 and our study was the chosen method to analyze the variability of successive RR intervals, and nonlinear methods, as we used, is reported to be more suitable to quantify complex phenomena such as control of cardiac function mediated by ANS 46 , 47 , Despite the great effort to control the variables involved in the study, some limitations should be considered.
One of the limitations of our findings is associated with the use of a cycle ergometer in the laboratory. Thus, the findings of the present study should be confirmed in additional research protocols, which use field tests i.
Other limitations of the present study are related to the analysis of the plasma catecholamine concentrations and the sympathetic nerve activity; however, we used HRV, a simple non-invasive method and one of the most promising quantitative markers of autonomic heart rate balance The urine content of caffeine metabolites paraxanthine, theobromine, and theophylline was also not analyzed in the present study, which could indirectly reflect the pharmacokinetics of CAF.
It has been shown that the increase in the concentration of paraxanthine one of the metabolites of CAF has a different relationship with plasma levels of CAF after the min period of CAF ingestion time used in the present study The increase in paraxanthine occurs at a slower rate than the CAF in plasma during this period 60 min , making its detection in urine even more difficult Finally, we do not control Cytochrome P CYP1A2 polymorphisms.
These variations in genes encoding CYP1A2 proteins can impact caffeine metabolism and potentiate dopaminergic neurotransmission. However, as this condition is uncommon, conducting a study with this genetic outcome requires a robust number of participants As a novelty from our study we highlight the use of a 16 km TT-test, a long task that mimetize cycling competitions tasks, instead of predominantly anaerobic tests, which have been used in previous studies, investigating the cardiovascular effects of CAF supplementation.
The use of symbolic analysis to estimate sympathovagal modulation, and the Bayesian inference as a statistical approach, also represent novelty, since previous studies in the field of our study did not include these promising mathematical approaches.
It is noteworthy that the cardioprotective effect of caffeine was observed in healthy volunteers, and our findings should not be transmitted to patients at high cardiovascular risk or cardiovascular disease.
Other studies must be carried out to assess the effects of different doses of CAF, and establish the most accurate dosage that enhances the results, favors cardioprotection, and minimizes risks.
Assuming repeated measures, within factors three interventions. The inclusion criteria were: all had at least 4 years of experience, participated in at least 20 competitions in and , have no history of cardiorespiratory, gastrointestinal, and musculoskeletal disorders in the last 3 months.
A simple questionnaire evaluated the training volume of all participants to warrant a homogenous sample for the study. In addition, a validated caffeine consumption questionnaire was administered to the participants, showing that all participants were moderate to high caffeine consumers The research protocol 2.
A randomized, double-blind, crossover, placebo-controlled design was used in this study. On the first visit to the laboratory, participants underwent dietary assessment and cycling test to exhaustion.
On the second visit, cyclists became familiar with the time trial test. So they received four visits from the researchers at home, one per day, for delivery and verification of capsule consumption according to randomization.
The other day they consumed the capsule acutely 60 min before the 16 km time trial test. The study preconized a seven-day washout between the different intervention strategies 19 , 20 , 21 , We tested the following strategies: Placebo—Placebo PP , participants received Placebo 4-day supplementation , and Placebo acute ingestion, 60 min before simulated cycling TT-test completed.
Placebo capsules were mg of magnesium silicate single daily dose. Placebo—Caffeine PC , participants received Placebo 4-day supplementation , and Caffeine acute ingestion, 60 min before simulated cycling TT-test completed.
Caffeine—Caffeine CC , participants received Caffeine 4-day supplementation , and Caffeine acute ingestion, 60 min before simulated cycling TT-test completed. At the first visit to the laboratory, the researchers verified the routine energy and caffeine intake of food, VO 2 max, and workload capacity in the graded test until exhaustion in the cycle ergometer.
The athletes were instructed to withdraw all their caffeine consumption i. On the test day, cyclists arrived fasting in the laboratory, and soon an intravenous cannula 20G Jelco; B.
Braun Medical Inc. Cyclists did not exercise 24 h before the experimental trials in the laboratory. The athletes were instructed to continue the routine of daily training. The experimental trials were performed at the same time of day a.
com Supplementary File -Disposition of study participants. To determine the VO 2 max, participants performed a graded exercise test to exhaustion on the cycle ergometer Cefise, São Paulo, Brazil. Heart rate was monitored continuously Polar Electro Oy, Kempele, Finland. The pulmonary gas exchange was determined breath by breath for carbon dioxide, oxygen concentrations, and minute ventilation using a VO gas analysis system MedGraphics, St.
Paul, MN, USA. The equipment was automatically calibrated according to the manufacturer's specifications before each test.
The present study determined and validated the VO 2 max following these criteria: increase in VO 2 less than 2.
Because the participants are used to consuming average amounts of caffeine daily, around In the presence of a researcher, all athletes were instructed to take a single capsule daily at the same time a. during the 4-day supplementation.
In acute ingestion, the capsule was administered with mL of water before simulated cycling TT-test completed. Supplements for each participant were prepared and separated by a non-affiliated researcher to ensure double-blinding. With this information, we would know the percentage of belief of caffeine consumption.
A high frequency of this belief could influence the study results as described by other authors Cyclists were instructed to maintain their dietary and hydration patterns. A h dietary record was completed by each athlete on the first visit and, before the first test, it was photocopied and returned to the athletes so that the same diet could be repeated for subsequent trials.
The energy intake, carbohydrates, total proteins, and total lipids was determined. The TACO database was used to quantify macronutrient intake and the Dietpro 5i software version 5. To assess the dietary frequency and the amount of caffeine, a validated questionnaire was applied by trained nutritionists.
The questionnaire consists of a list of dietary sources of CAF coffee, tea, cocoa, chocolate, soft drinks, medicines, and dietary supplements and the time of consumption.
Household measures were used to assess the amount of food consumed according to the following frequency of consumption Types of foods, dietary supplements, and medications that contained caffeine were identified.
The CAF content was obtained from the U. Successive RR intervals were acquired for 5 min while supine REST and along the TT-test. Beat-to-beat intervals were recorded by a validated heart rate monitor Polar RS, Polar Electro Oy, Kempele, Finland for HRV analysis The sampling frequency was set at Hz, the smoothness prior method with alpha set at was used for detrended the R-R intervals series.
They were studied 48 h far away from the last bout of physical exercise to avoid the short-term autonomic and cardiovascular confounding after-effects induced by recent training sessions.
Recordings at supine position HRV-SP were performed three times, before the ingestion of the capsule PRE suppl , 60 min after supplementation PRE exerc , and 10 min after the TT-test POST.
Recording of the HRV during the TT-test HRV-TT was done during the entire time of the exercise execution. The nonlinear dynamics of successive RR intervals were assessed by symbolic analysis 29 during the TT-test.
The R-R dynamics were classified into three pattern families: I patterns with no variation V0; all three symbols were equal ; II patterns with one variation V1; two consequent symbols were equal, and the remaining symbol was different ; and III patterns with two unlike or like variations V2; all of the symbols were different from the previous ones.
The percentage of the patterns V0 was calculated as sympathetic modulation predominance, V1 reflects sympathetic and parasympathetic modulation, and the V2 calculated as a parasympathetic modulation as suggested by Santos et al. The data i. For the recordings from supine position, the 5-min successive RR intervals were selected for analysis, while for TT-test, the visual inspection was carried out to find and select a segment of successive RR intervals where the stationarity of the time series was acceptable at three moments: beginning, midway and final of each TT-test session.
All RR interval variability analyses were carried out by the same researcher which was blind for the applied treatment in each data set. The measurement of blood levels of caffeine was performed at baseline and 60 min after intake of capsules.
Serum was obtained by centrifugation at 2. The caffeine blood levels were determined using a HPLC method previously described The HPLC analyses were carried out using a Shimadzu chromatograph Shimadzu Corp. Participants did not receive any performance feedback during the tests.
The only information that the participants received was the distance reached: 2 km, 4 km, 6 km, 8 km, 10 km, 12 km, 14 km, and 16 km. The analyses of the power outputs were measured in 3 equals intervals Beginning, Midway and Final of the completed TT-test time curve.
The dynamics of data acquisition in the laboratory can be seen in Fig. Dynamics of data acquisition. Placebo—Placebo PP , Placebo—Caffeine PC and Caffeine—Caffeine CC conditions were tested in 16 km time Trial 16 km TT performance and HRV analysis were done pre supplementation HRV-SP PRE suppl , post supplementation HRV-SP POST suppl during 16 km TT HRV-TT and post 16 km TT HRV-SP Post.
When data showed normal distribution the variables were analyzed by mixed ANOVA with repeated measures. The Mauchly sphericity test was performed for all tested variables, and the Greenhouse—Geisser correction was used in cases where the sphericity assumption was violated.
Tukey's post hoc test was used for means multiple comparisons. When data presented a non-normal distribution the Kruskal Wallis test was used version To check the qualitative outcomes and the probability to replicate the same results i.
The posterior odds have been corrected for multiple testing by fixing to 0. The "U" in the Bayes factor denotes that it is uncorrected. We made all BF analysis through the JAMOVI. Mitchell, D. Beverage caffeine intakes in the U. Food Chem.
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Front Sports Act Living 2 , Dodd, S. In this study MOEn was estimated applying SampEn algorithm in the mechanical power output signal obtained during TT 4km.
A custom code Matlab v. This improved power output in caffeine was reflected in ~1. Additionally, cyclists presented comparable mean RPE during the TT 4km in both supplementations with caffeine 16 ± 0. and placebo 16 ± 0. Mechanical power output panel A and motor output entropy panel B in placebo and caffeine trials.
Mechanical power output relative to a percentage of the TT 4km distance. Fig 3 depicts MOEn responses during the cycling trial, and Table 1 shows individual power output and MOEn responses over the TT 4km in both supplementations.
Motor output entropy was expressed relative to a percentage of the TT 4km distance. Table 2 shows all correlation coefficients between MOEn and power output. This study aimed to characterize the MOEn during a TT 4km and investigate if caffeine could change the MOEn-fatigue interplay during this strenuous, whole-body short cycling exercise.
Our results showed a progressive reduction in motor output complexity as the TT 4km progressed, however caffeine increased TT 4km performance through an altered MOEn-fatigue interplay. These results may support the notion that caffeine increases power output responses and attenuates the fatigue-induced reduction in MOEn during TT 4km.
This is the first study characterizing the MOEn during a natural exercise mode with high ecological validity such as a strenuous, whole-body short cycling time trial. Briefly, MOEn responses could involve changes in neuromuscular complexity such as in CNS areas such as cortical, subcortical and spinal areas, as well as in motor neuron conduction to skeletal muscles.
However, despite the increasing exercise-induced perturbation, neuromuscular fatigue was likely low over this half of the trial and probably allowed an increased MOEn when regulating the motor output during this part [ 40 ]. One may argue that neuromuscular fatigue is low during this initial part of the trial, thus likely allowing an adequate response of the neuromuscular system to the exercise-imposed perturbation through an increased motor unit firing variability.
In contrast, such a correlation between power output and MOEn was not observed in placebo TT 4km during these parts. This is a part of the cycling trial usually characterized by a sharp increase in power output i. end spurt , so that one may hypothesize that the loss of MOEn during this latter part of the TT 4km was possibly related to a higher motor unit firing frequency, as neuromuscular fatigue is higher in the second half of a cycling trial [ 40 ].
A short cycling time trial having an end spurt may be a challenging scenario for the neuromuscular system, as this may represent fewer chances to vary muscle recruitment during pedaling mainly at the final stages of the trial [ 18 ], thereby reducing the mechanical power output variability i.
power output bandwidth and MOEn. This hypothesis is based on a previous study that reported a different neuromuscular strategy as indicated by EMG analysis when contrasting fixed-load cycling at W vs W [ 18 ].
The authors of that study concluded that the lower EMG entropy observed during higher cycling power output was likely due to a higher synchronism of motor units firing. The present study hypothesized that caffeine may increase MOEn by increasing motoneuronal gain and changing the input-output relationship in the motor pathway, thereby resulting in a greater variability in motor output.
Although caffeine effects on skeletal muscles cannot be ruled out [ 41 ], the most convincing caffeine mechanism involves its action on neuronal A 1 adenosine receptors, as improvements in exercise performance after caffeine ingestion have been associated with increases in spinal and supraspinal excitability [ 42 , 43 ].
Analysis of movement variability have been used in different research fields [ 1 , 2 , 44 ], so that such analysis have been recently incorporated in neuromuscular fatigue studies [ 5 , 6 ].
In an exercise performance scenario, nonlinear measures such as MOEn may be a useful mean to estimate exercise-induced neuromuscular fatigue and its repercussion on motor control and performance responses [ 5 ].
Therefore, such a nonlinear measure could be helpful to improve the understanding of exercise performance and fatigue in different fields of sports sciences. The increased motoneuronal gain suggestion should be interpreted with caution, as no specific measures were performed to indicate motoneuronal gain.
Insights to a motoneuronal gain mechanism could be obtained with advanced EMG techniques, such as the motor unit decomposition algorithms from electrode matrices-derived signal [ 45 ].
However, this technique is still restricted to low-intensity isometric contractions so that the dynamic whole-body exercise used in the present study limited the use of these measures to provide motoneuronal gain mechanisms insights after caffeine ingestion. Future studies comparing recruitment and de-recruitment frequencies of pairs of motor units could shed-light on caffeine effects on motoneuronal gain during voluntary contractions [ 46 ].
The present study is descriptive rather than mechanistic, and its design and methods may not elucidate if losses in power output entropy during cycling time trial were due to central or peripheral fatigue factors.
In this sense, the power output was sampled at a 2 Hz frequency, a sampling rate that may not detect all variability in power output data, given the possible aliasing effect resulted from sampling the data in different pedal positions at each revolution. Another limitation was the absence of EMG responses, a measure that could have assessed the neuromuscular system and power output entropy, simultaneously.
However, considering that habitual caffeine consumption may change physiological responses to caffeine supplementation such as heart rate and ventilation, future studies may want to investigate potential habitual caffeine consumption effects on MOEn and EMG during cycling time trial.
However, caffeine ingestion improved TT 4km performance and MOEn. These results reinforce a likely fatigue-induced loss of complexity hypothesis.
Browse Subject Areas? Click through the PLOS taxonomy to find articles in your field. Article Authors Metrics Comments Media Coverage Reader Comments Figures. Correction 22 Jan Viana BF, Trajano GS, Ugrinowitsch C, Pires FO Correction: Caffeine increases motor output entropy and performance in 4 km cycling time trial.
Abstract Caffeine improves cycling time trial performance through enhanced motor output and muscle recruitment. Introduction According to the dynamic system theory, the variability presented by a given physiological system, a concept that is known as complexity, may reflect its flexibility to face natural perturbations [ 1 , 2 ].
Methods Participants and experimental design Nine endurance-trained male cyclists Caffeine and placebo ingestion Caffeine and placebo capsules 6 mg. Instruments, measures, and analysis All cyclists performed the TT 4km on the same road bike Giant®, Thousand Oaks, CA, USA attached to a cycle-simulator calibrated before every test Racer Mate®, Computrainer, Seattle, WA, EUA , individually fitted with crank, pedals and saddle.
Entropy calculation The entropy could be interpreted as a non-linear analysis that provides a measure of the complexity of a system [ 35 ].
Data analysis and statistics In this study MOEn was estimated applying SampEn algorithm in the mechanical power output signal obtained during TT 4km.
Download: PPT. Table 1. Individual power output PO and motor output entropy MOEn responses were reported as a percentage of the total cycling time trial distance. Table 2. Discussion This study aimed to characterize the MOEn during a TT 4km and investigate if caffeine could change the MOEn-fatigue interplay during this strenuous, whole-body short cycling exercise.
Limitations and methodological considerations The increased motoneuronal gain suggestion should be interpreted with caution, as no specific measures were performed to indicate motoneuronal gain. Supporting information. S1 Raw data. s XLSX. References 1. Lipsitz L. and Goldberger A. Loss of; complexity; and aging: Potential applications of fractals and chaos theory to senescence.
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Journal of the International Society ppwer Sports Nutrition volume CaffenieArticle number: Caffeine and power output Cite this Herbal joint support. Metrics details. Caffeine is commonly Caffeine and power output Caffeins an ergogenic aid. Literature pwer the effects of caffeine ingestion on muscle strength Organic weight loss supplements power is equivocal. Caffeihe aim of this systematic review and meta-analysis was to summarize results from individual studies on the effects of caffeine intake on muscle strength and power. A search through eight databases was performed to find studies on the effects of caffeine on: i maximal muscle strength measured using 1 repetition maximum tests; and ii muscle power assessed by tests of vertical jump. Meta-analyses of standardized mean differences SMD between placebo and caffeine trials from individual studies were conducted using the random effects model.
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