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Antonio J, Newmire DE, Stout JR, Antonio B, Gibbons M, Lowery LM, Harper J, Willoughby D, Evans C, Anderson D, Goldstein E, Rojas J, Monsalves-Álvarez M, Forbes SC, Gomez Lopez J, Ziegenfuss T, Moulding BD, Candow D, Sagner M, Arent SM. Common questions and misconceptions about caffeine supplementation: what does the scientific evidence really show? J Int Soc Sports Nutr 2024; 21:2323919. [PMID: 38466174 DOI: 10.1080/15502783.2024.2323919] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Accepted: 02/17/2024] [Indexed: 03/12/2024] Open
Abstract
Caffeine is a popular ergogenic aid that has a plethora of evidence highlighting its positive effects. A Google Scholar search using the keywords "caffeine" and "exercise" yields over 200,000 results, emphasizing the extensive research on this topic. However, despite the vast amount of available data, it is intriguing that uncertainties persist regarding the effectiveness and safety of caffeine. These include but are not limited to: 1. Does caffeine dehydrate you at rest? 2. Does caffeine dehydrate you during exercise? 3. Does caffeine promote the loss of body fat? 4. Does habitual caffeine consumption influence the performance response to acute caffeine supplementation? 5. Does caffeine affect upper vs. lower body performance/strength differently? 6. Is there a relationship between caffeine and depression? 7. Can too much caffeine kill you? 8. Are there sex differences regarding caffeine's effects? 9. Does caffeine work for everyone? 10. Does caffeine cause heart problems? 11. Does caffeine promote the loss of bone mineral? 12. Should pregnant women avoid caffeine? 13. Is caffeine addictive? 14. Does waiting 1.5-2.0 hours after waking to consume caffeine help you avoid the afternoon "crash?" To answer these questions, we performed an evidence-based scientific evaluation of the literature regarding caffeine supplementation.
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Affiliation(s)
- Jose Antonio
- Nova Southeastern University, Department of Health and Human Performance, Davie, FL, USA
| | - Daniel E Newmire
- Texas Woman's University, Exercise Physiology and Biochemistry Laboratory, School of Health Promotion and Kinesiology, Denton, TX, USA
| | - Jeffrey R Stout
- University of Central Florida, College of Health Professions and Sciences, Orlando, FL, USA
| | - Brandi Antonio
- University of Central Florida, College of Health Professions and Sciences, Orlando, FL, USA
| | | | - Lonnie M Lowery
- Nutrition, Exercise and Wellness Associates, Cuyahoga Falls, OH, USA
- Walsh University, Department of Exercise Science, North Canton, OH, USA
| | - Joseph Harper
- Walsh University, Department of Exercise Science, North Canton, OH, USA
| | - Darryn Willoughby
- School of Exercise and Sport Science, University of Mary Hardin-Baylor, Belton, TX, USA
| | - Cassandra Evans
- Nova Southeastern University, Department of Health and Human Performance, Davie, FL, USA
| | - Dawn Anderson
- Indiana Tech, Exercise and Sport Performance Laboratory, Fort Wayne, IN, USA
| | - Erica Goldstein
- Stetson University, Department of Health Sciences, Deland, FL, USA
| | - Jose Rojas
- Keiser University, Fort Lauderdale, FL, USA
- Rocky Mountain University of Health Professions, Provo, UT, USA
| | - Matías Monsalves-Álvarez
- Universidad de O´Higgins, Exercise Metabolism and Nutrition Laboratory. Instituto de Ciencias de la Salud, Rancagua, Chile
- Motion Human Performance Laboratory, Lo Barnechea, Chile
| | - Scott C Forbes
- Brandon University, Department of Physical Education Studies, CBrandon, MB, Canada
| | | | - Tim Ziegenfuss
- The Center for Applied Health Sciences, Canfield, OH, USA
| | - Blake D Moulding
- University of Regina, Faculty of Kinesiology and Health Studies, Regina, SK, Canada
| | - Darren Candow
- University of Regina, Faculty of Kinesiology and Health Studies, Regina, SK, Canada
| | | | - Shawn M Arent
- University of South Carolina, Arnold School of Public Health, Columbia, SC, USA
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John K, Kathuria S, Peel J, Page J, Aitkenhead R, Felstead A, Heffernan SM, Jeffries O, Tallent J, Waldron M. Caffeine ingestion compromises thermoregulation and does not improve cycling time to exhaustion in the heat amongst males. Eur J Appl Physiol 2024; 124:2489-2502. [PMID: 38568259 DOI: 10.1007/s00421-024-05460-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Accepted: 03/04/2024] [Indexed: 08/16/2024]
Abstract
PURPOSE Caffeine is a commonly used ergogenic aid for endurance events; however, its efficacy and safety have been questioned in hot environmental conditions. The aim of this study was to investigate the effects of acute caffeine supplementation on cycling time to exhaustion and thermoregulation in the heat. METHODS In a double-blind, randomised, cross-over trial, 12 healthy caffeine-habituated and unacclimatised males cycled to exhaustion in the heat (35 °C, 40% RH) at an intensity associated with the thermoneutral gas exchange threshold, on two separate occasions, 60 min after ingesting caffeine (5 mg/kg) or placebo (5 mg/kg). RESULTS There was no effect of caffeine supplementation on cycling time to exhaustion (TTE) (caffeine; 28.5 ± 8.3 min vs. placebo; 29.9 ± 8.8 min, P = 0.251). Caffeine increased pulmonary oxygen uptake by 7.4% (P = 0.003), heat production by 7.9% (P = 0.004), whole-body sweat rate (WBSR) by 21% (P = 0.008), evaporative heat transfer by 16.5% (P = 0.006) and decreased estimated skin blood flow by 14.1% (P < 0.001) compared to placebo. Core temperature was higher by 0.6% (P = 0.013) but thermal comfort decreased by - 18.3% (P = 0.040), in the caffeine condition, with no changes in rate of perceived exertion (P > 0.05). CONCLUSION The greater heat production and storage, as indicated by a sustained increase in core temperature, corroborate previous research showing a thermogenic effect of caffeine ingestion. When exercising at the pre-determined gas exchange threshold in the heat, 5 mg/kg of caffeine did not provide a performance benefit and increased the thermal strain of participants.
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Affiliation(s)
- Kevin John
- Research Institute for Sport and Exercise, University of Canberra, Canberra, Australia
- Applied Sports Science Technology and Medicine Research Centre (A-STEM), Faculty of Science and Engineering, Bay Campus, Swansea University, Swansea, Wales, SA1 8EN, UK
| | - Sayyam Kathuria
- Applied Sports Science Technology and Medicine Research Centre (A-STEM), Faculty of Science and Engineering, Bay Campus, Swansea University, Swansea, Wales, SA1 8EN, UK
| | - Jenny Peel
- Applied Sports Science Technology and Medicine Research Centre (A-STEM), Faculty of Science and Engineering, Bay Campus, Swansea University, Swansea, Wales, SA1 8EN, UK
| | - Joe Page
- Applied Sports Science Technology and Medicine Research Centre (A-STEM), Faculty of Science and Engineering, Bay Campus, Swansea University, Swansea, Wales, SA1 8EN, UK
| | - Robyn Aitkenhead
- Applied Sports Science Technology and Medicine Research Centre (A-STEM), Faculty of Science and Engineering, Bay Campus, Swansea University, Swansea, Wales, SA1 8EN, UK
| | - Aimee Felstead
- Applied Sports Science Technology and Medicine Research Centre (A-STEM), Faculty of Science and Engineering, Bay Campus, Swansea University, Swansea, Wales, SA1 8EN, UK
| | - Shane M Heffernan
- Applied Sports Science Technology and Medicine Research Centre (A-STEM), Faculty of Science and Engineering, Bay Campus, Swansea University, Swansea, Wales, SA1 8EN, UK
| | - Owen Jeffries
- School of Biomedical, Nutritional and Sport Sciences, Newcastle University, Newcastle Upon Tyne, UK
| | - Jamie Tallent
- School of Sport, Rehabilitation, and Exercise Sciences, University of Essex, Colchester, UK
- Department of Physiotherapy, Faculty of Medicine, Nursing and Health Sciences, School of Primary and Allied Health Care, Monash University, Clayton, Australia
| | - Mark Waldron
- Applied Sports Science Technology and Medicine Research Centre (A-STEM), Faculty of Science and Engineering, Bay Campus, Swansea University, Swansea, Wales, SA1 8EN, UK.
- Welsh Institute of Performance Science, Swansea University, Swansea, UK.
- School of Health and Behavioural Sciences, University of the Sunshine Coast, Sippy Down, QLD, Australia.
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Wang J, Dewi L, Peng Y, Hou CW, Song Y, Condello G. Does ergogenic effect of caffeine supplementation depend on CYP1A2 genotypes? A systematic review with meta-analysis. JOURNAL OF SPORT AND HEALTH SCIENCE 2024; 13:499-508. [PMID: 38158179 PMCID: PMC11184386 DOI: 10.1016/j.jshs.2023.12.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 10/28/2023] [Accepted: 11/29/2023] [Indexed: 01/03/2024]
Abstract
BACKGROUND The ergogenic effects of caffeine intake on exercise performance are well-established, even if differences exist among individuals in response to caffeine intake. The genetic variation of a specific gene, human cytochrome P450 enzyme 1A2 (CYP1A2) (rs762551), may be one reason for this difference. This systematic review and meta-analysis aimed to comprehensively evaluate the influence of CYP1A2 gene types on athletes' exercise performance after caffeine intake. METHODS A literature search through 4 databases (Web of Science, PubMed, Scopus, and China National Knowledge Infrastructure) was conducted until March 2023. The effect size was expressed as the weighted mean difference (WMD) by calculating fixed effects meta-analysis if heterogeneity was not significant (I2 ≤ 50% and p ≥ 0.1). Subgroup analyses were performed based on AA and AC/CC genotype of CYP1A2. RESULTS The final number of studies meeting the inclusion criteria was 12 (n = 666 participants). The overall analysis showed that the cycling time trial significantly improved after caffeine intake (WMD = -0.48, 95% confidence interval (95%CI): -0.83 to -0.13, p = 0.007). In subgroup analyses, acute caffeine intake improved cycling time trial only in individuals with the A allele (WMD = -0.90, 95%CI: -1.48 to -0.33, p = 0.002), but not the C allele (WMD = -0.08, 95%CI: -0.32 to 0.17, p = 0.53). Caffeine supplementation did not influence the Wingate (WMD = 8.07, 95%CI: -22.04 to 38.18, p = 0.60) or countermovement jump test (CMJ) performance (WMD = 1.17, 95%CI: -0.02 to 2.36, p = 0.05), and these outcomes were not influenced by CYP1A2 genotype. CONCLUSION Participants with the CYP1A2 genotype with A allele improved their cycling time trials after caffeine supplementation. However, compared to placebo, acute caffeine supplementation failed to increase the Wingate or CMJ performance, regardless of CYP1A2 genotype.
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Affiliation(s)
- Jieping Wang
- Laboratory of Exercise Biochemistry, University of Taipei, Tianmu Campus, Taipei 11153, China; Department of Emergency Medicine, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha 410008, China
| | - Luthfia Dewi
- Laboratory of Exercise Biochemistry, University of Taipei, Tianmu Campus, Taipei 11153, China; Department of Nutrition, Universitas Muhammadiyah Semarang, Semarang 50273, Indonesia
| | - Yundong Peng
- School of Sports Medicine and Rehabilitation, Beijing Sport University, Beijing 10084, China
| | - Chien-Wen Hou
- Laboratory of Exercise Biochemistry, University of Taipei, Tianmu Campus, Taipei 11153, China
| | - Yanmin Song
- Department of Emergency Medicine, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha 410008, China.
| | - Giancarlo Condello
- Department of Medicine and Surgery, University of Parma, Parma 43126, Italy
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Yang Y, Feng Z, Luo YH, Chen JM, Zhang Y, Liao YJ, Jiang H, Long Y, Wei B. Exercise-Induced Central Fatigue: Biomarkers, and Non-Medicinal Interventions. Aging Dis 2024:AD.2024.0567. [PMID: 39012671 DOI: 10.14336/ad.2024.0567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2024] [Accepted: 06/27/2024] [Indexed: 07/17/2024] Open
Abstract
Fatigue, commonly experienced in daily life, is a feeling of extreme tiredness, shortage or lack of energy, exhaustion, and difficulty in performing voluntary tasks. Central fatigue, defined as a progressive failure to voluntarily activate the muscle, is typically linked to moderate- or light-intensity exercise. However, in some instances, high-intensity exercise can also trigger the onset of central fatigue. Exercise-induced central fatigue often precedes the decline in physical performance in well-trained athletes. This leads to a reduction in nerve impulses, decreased neuronal excitability, and an imbalance in brain homeostasis, all of which can adversely impact an athlete's performance and the longevity of their sports career. Therefore, implementing strategies to delay the onset of exercise-induced central fatigue is vital for enhancing athletic performance and safeguarding athletes from the debilitating effects of fatigue. In this review, we discuss the structural basis, measurement methods, and biomarkers of exercise-induced central fatigue. Furthermore, we propose non-pharmacological interventions to mitigate its effects, which can potentially foster improvements in athletes' performances in a healthful and sustainable manner.
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Affiliation(s)
- Ying Yang
- Institute of Translational Medicine, School of Basic Medical, Department of Special Medicine, School of Public Health, Hengyang Medical College, University of South China, Hengyang, 421001, China
| | - Zhi Feng
- Institute of Translational Medicine, School of Basic Medical, Department of Special Medicine, School of Public Health, Hengyang Medical College, University of South China, Hengyang, 421001, China
| | - Yu-Hang Luo
- Institute of Translational Medicine, School of Basic Medical, Department of Special Medicine, School of Public Health, Hengyang Medical College, University of South China, Hengyang, 421001, China
| | - Jue-Miao Chen
- Institute of Translational Medicine, School of Basic Medical, Department of Special Medicine, School of Public Health, Hengyang Medical College, University of South China, Hengyang, 421001, China
| | - Yu Zhang
- Institute of Translational Medicine, School of Basic Medical, Department of Special Medicine, School of Public Health, Hengyang Medical College, University of South China, Hengyang, 421001, China
| | - Yi-Jun Liao
- Institute of Translational Medicine, School of Basic Medical, Department of Special Medicine, School of Public Health, Hengyang Medical College, University of South China, Hengyang, 421001, China
| | - Hui Jiang
- Institute of Translational Medicine, School of Basic Medical, Department of Special Medicine, School of Public Health, Hengyang Medical College, University of South China, Hengyang, 421001, China
| | - Yinxi Long
- Department of Neurology, Affiliated Hengyang Hospital of Hunan Normal University &;amp Hengyang Central Hospital, Hengyang, 421001, China
| | - Bo Wei
- Institute of Translational Medicine, School of Basic Medical, Department of Special Medicine, School of Public Health, Hengyang Medical College, University of South China, Hengyang, 421001, China
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Ferreira LHB, Forbes SC, Barros MP, Smolarek AC, Enes A, Lancha-Junior AH, Martins GL, Souza-Junior TP. High Doses of Caffeine Increase Muscle Strength and Calcium Release in the Plasma of Recreationally Trained Men. Nutrients 2022; 14:4921. [PMID: 36432607 PMCID: PMC9697598 DOI: 10.3390/nu14224921] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Revised: 11/15/2022] [Accepted: 11/17/2022] [Indexed: 11/22/2022] Open
Abstract
The effects of acute caffeine supplementation on muscular strength remain unclear. We examined the effects of two different doses of caffeine on muscle strength and calcium in plasma compared to placebo using a crossover, randomized, double-blind, placebo-controlled design. Twenty-one (n = 21) recreationally resistance-trained participants were randomly assigned into three experimental conditions: 6 mg·kg bw−1 of caffeine (CF6); 8 mg·kg bw−1 of caffeine (CF8); or placebo (PLA), with a 7-day washout period between conditions. Muscular strength assessments were made for both upper (bench press) and lower body muscles (squat and deadlift). Calcium release in plasma was measured on five different occasions. Bench press (CF8: 100.1 ± 1.9 kg; PLA: 94.2 ± 2.5 kg), deadlift (CF8: 132.8 ± 3.5 kg; PLA: 120.7 ± 5.7 kg), and squat (CF8: 130.1 ± 4.9 kg; PLA 119.4 ± 5.4 kg) strength were all significantly (p < 0.001) improved in CF8 compared to PLA. Calcium release in plasma was significantly increased in CF8, whereas no changes were observed in CF6 or PLA. Overall, 8 mg·kg bw−1 of caffeine appears to be an effective dose to optimize upper and lower body muscular strength and calcium release in recreationally trained participants.
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Affiliation(s)
- Luis H. B. Ferreira
- Metabolism, Nutrition and Strength Training Research Group (GPMENUTF), Federal University of Paraná (UFPR), Curitiba 81531-980, PR, Brazil
| | - Scott C. Forbes
- Department of Physical Education Studies, Brandon University, Brandon, MB R7A 6A9, Canada
| | - Marcelo P. Barros
- Institute of Physical Activity Sciences and Sports, Universidade Cruzeiro do Sul, São Paulo 07115-000, SP, Brazil
| | - André C. Smolarek
- Metabolism, Nutrition and Strength Training Research Group (GPMENUTF), Federal University of Paraná (UFPR), Curitiba 81531-980, PR, Brazil
| | - Alysson Enes
- Metabolism, Nutrition and Strength Training Research Group (GPMENUTF), Federal University of Paraná (UFPR), Curitiba 81531-980, PR, Brazil
| | - Antonio H. Lancha-Junior
- Laboratory of Clinical Investigation: Experimental Surgery (LIM 26), Clinic’s Hospital of Medical School, University of Sao Paulo, Sao Paulo 05508-030, SP, Brazil
| | - Gabriel L. Martins
- Laboratory of Clinical Investigation: Experimental Surgery (LIM 26), Clinic’s Hospital of Medical School, University of Sao Paulo, Sao Paulo 05508-030, SP, Brazil
| | - Tacito P. Souza-Junior
- Metabolism, Nutrition and Strength Training Research Group (GPMENUTF), Federal University of Paraná (UFPR), Curitiba 81531-980, PR, Brazil
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Naulleau C, Jeker D, Pancrate T, Claveau P, Deshayes TA, Burke LM, Goulet EDB. Effect of Pre-Exercise Caffeine Intake on Endurance Performance and Core Temperature Regulation During Exercise in the Heat: A Systematic Review with Meta-Analysis. Sports Med 2022; 52:2431-2445. [PMID: 35616851 DOI: 10.1007/s40279-022-01692-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/17/2022] [Indexed: 11/26/2022]
Abstract
BACKGROUND Heat is associated with physiological strain and endurance performance (EP) impairments. Studies have investigated the impact of caffeine intake upon EP and core temperature (CT) in the heat, but results are conflicting. There is a need to systematically determine the impact of pre-exercise caffeine intake in the heat. OBJECTIVE To use a meta-analytical approach to determine the effect of pre-exercise caffeine intake on EP and CT in the heat. DESIGN Systematic review with meta-analysis. DATA SOURCES Four databases and cross-referencing. DATA ANALYSIS Weighted mean effect summaries using robust variance random-effects models for EP and CT, as well as robust variance meta-regressions to explore confounders. STUDY SELECTION Placebo-controlled, randomized studies in adults (≥ 18 years old) with caffeine intake at least 30 min before endurance exercise ≥ 30 min, performed in ambient conditions ≥ 27 °C. RESULTS Respectively six and 12 studies examined caffeine's impact on EP and CT, representing 52 and 205 endurance-trained individuals. On average, 6 mg/kg body mass of caffeine were taken 1 h before exercises of ~ 70 min conducted at 34 °C and 47% relative humidity. Caffeine supplementation non-significantly improved EP by 2.1 ± 0.8% (95% CI - 0.7 to 4.8) and significantly increased the rate of change in CT by 0.10 ± 0.03 °C/h (95% CI 0.02 to 0.19), compared with the ingestion of a placebo. CONCLUSION Caffeine ingestion of 6 mg/kg body mass ~ 1 h before exercise in the heat may provide a worthwhile improvement in EP, is unlikely to be deleterious to EP, and trivially increases the rate of change in CT.
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Affiliation(s)
- Catherine Naulleau
- Performance, Hydration and Thermoregulation Laboratory, Faculty of Physical Activity Sciences, University of Sherbrooke, 2500 boul. de l'Université, Sherbrooke, P.Q., J1K 2R1, Canada
- Institut National du Sport du Québec, Montréal, P.Q., Canada
| | - David Jeker
- Performance, Hydration and Thermoregulation Laboratory, Faculty of Physical Activity Sciences, University of Sherbrooke, 2500 boul. de l'Université, Sherbrooke, P.Q., J1K 2R1, Canada
- Institut National du Sport du Québec, Montréal, P.Q., Canada
| | - Timothée Pancrate
- Performance, Hydration and Thermoregulation Laboratory, Faculty of Physical Activity Sciences, University of Sherbrooke, 2500 boul. de l'Université, Sherbrooke, P.Q., J1K 2R1, Canada
| | - Pascale Claveau
- Performance, Hydration and Thermoregulation Laboratory, Faculty of Physical Activity Sciences, University of Sherbrooke, 2500 boul. de l'Université, Sherbrooke, P.Q., J1K 2R1, Canada
| | - Thomas A Deshayes
- Performance, Hydration and Thermoregulation Laboratory, Faculty of Physical Activity Sciences, University of Sherbrooke, 2500 boul. de l'Université, Sherbrooke, P.Q., J1K 2R1, Canada
- Research Center on Aging, University of Sherbrooke, Sherbrooke, P.Q., Canada
| | - Louise M Burke
- Mary MacKillop Institute for Health Research, Australian Catholic University, Melbourne, VIC, Australia
| | - Eric D B Goulet
- Performance, Hydration and Thermoregulation Laboratory, Faculty of Physical Activity Sciences, University of Sherbrooke, 2500 boul. de l'Université, Sherbrooke, P.Q., J1K 2R1, Canada.
- Research Center on Aging, University of Sherbrooke, Sherbrooke, P.Q., Canada.
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Can I Have My Coffee and Drink It? A Systematic Review and Meta-analysis to Determine Whether Habitual Caffeine Consumption Affects the Ergogenic Effect of Caffeine. Sports Med 2022; 52:2209-2220. [PMID: 35536449 DOI: 10.1007/s40279-022-01685-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/29/2022] [Indexed: 01/04/2023]
Abstract
OBJECTIVE The aim was to quantify the proportion of the literature on caffeine supplementation that reports habitual caffeine consumption, and determine the influence of habitual consumption on the acute exercise response to caffeine supplementation, using a systematic review and meta-analytic approach. METHODS Three databases were searched, and articles screened according to inclusion/exclusion criteria. Three-level meta-analyses and meta-regression models were used to investigate the influence of habitual caffeine consumption on caffeine's overall ergogenic effect and within different exercise types (endurance, power, strength), in men and women, and in trained and untrained individuals. Sub-analyses were performed according to the following: acute relative dose (< 3, 3-6, > 6 mg/kg body mass [BM]); whether the acute caffeine dose provided was lower or higher than the mean daily caffeine dose; and the caffeine withdrawal period prior to the intervention (< 24, 24-48, > 48 h). RESULTS Sixty caffeine studies included sufficient information on habitual consumption to be included in the meta-analysis. A positive overall effect of caffeine was shown in comparison to placebo (standard mean difference [SMD] = 0.25, 95% confidence interval [CI] 0.20-0.30; p < 0.001) with no influence of relative habitual caffeine consumption (p = 0.59). Subgroup analyses showed a significant ergogenic effect when the caffeine dose was < 3 mg/kg BM (SMD = 0.26, 95% CI 0.12-0.40; p = 0.003) and 3-6 mg/kg BM (SMD = 0.26, 95% CI 0.21-0.32; p < 0.0001), but not > 6 mg/kg BM (SMD = 0.11, 95% CI - 0.07 to 0.30; p = 0.23); when the dose was both higher (SMD = 0.26, 95% CI 0.20-0.31; p < 0.001) and lower (SMD = 0.21, 95% CI 0.06-0.36; p = 0.006) than the habitual caffeine dose; and when withdrawal was < 24 h, 24-48 h, and > 48 h. Caffeine was effective for endurance, power, and strength exercise, with no influence (all p ≥ 0.23) of relative habitual caffeine consumption within exercise types. Habitual caffeine consumption did not modify the ergogenic effect of caffeine in male, female, trained or untrained individuals. CONCLUSION Habitual caffeine consumption does not appear to influence the acute ergogenic effect of caffeine.
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Hunt LA, Hospers L, Smallcombe JW, Mavros Y, Jay O. Caffeine alters thermoregulatory responses to exercise in the heat only in caffeine-habituated individuals: a double-blind placebo-controlled trial. J Appl Physiol (1985) 2021; 131:1300-1310. [PMID: 34435513 DOI: 10.1152/japplphysiol.00172.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
To assess the impact of acute caffeine ingestion on thermoregulatory responses during steady-state exercise under moderate heat stress conditions in caffeine-habituated and nonhabituated individuals. Twenty-eight participants [14 habituated (HAB) (4 females) and 14 nonhabituated (NHAB) (6 females)] cycled at a fixed metabolic heat production (7 W·kg-1) for 60 min on two separate occasions 1 h after ingesting 1) 5 mg·kg-1 caffeine (CAF) or 2) 5 mg·kg-1 placebo (PLA), in a double-blinded, randomized, and counterbalanced order. Environmental conditions were 30.6 ± 0.9°C, 31 ± 1% relative humidity (RH). The end-exercise rise in esophageal temperature (ΔTes) from baseline was greater with CAF in the HAB group (CAF = 0.88 ± 0.29°C, PLA = 0.62 ± 0.34°C, P < 0.001), but not in the NHAB group (CAF = 1.00 ± 0.42°C, PLA = 1.00 ± 0.39°C, P = 0.94). For a given change in mean body temperature, rises in % of maximum skin blood flow were attenuated with CAF on the forearm (P = 0.015) and back (P = 0.021) in the HAB group, but not in the NHAB group (P ≥ 0.65). Dry heat loss was similar in the HAB (CAF = 31 ± 5 W·m-2, PLA = 33 ± 7 W·m-2) and NHAB groups (CAF = 31 ± 3 W·m-2, PLA 30 ± 4 W·m-2) (P ≥ 0.37). There were no differences in whole body sweat losses in both groups (HAB: CAF = 0.59 ± 0.15 kg, PLA = 0.56 ± 0.17 kg, NHAB:CAF = 0.53 ± 0.19 kg, PLA 0.52 ± 0.19 kg) (P ≥ 0.32). As the potential for both dry and evaporative heat loss was uninhibited by caffeine, we suggest that the observed ΔTes differences with CAF in the HAB group were due to alterations in internal heat distribution. Our findings support the common practice of participants abstaining from caffeine before participation in thermoregulatory research studies in compensable conditions.NEW & NOTEWORTHY We provide empirical evidence that acute caffeine ingestion exerts a thermoregulatory effect during exercise in the heat in caffeine-habituated individuals but not in nonhabituated individuals. Specifically, caffeine habituation was associated with a greater rise in esophageal temperature with caffeine compared with placebo, which appears to be driven by a blunted skin blood flow response. In contrast, no thermoregulatory differences were observed with caffeine in nonhabituated individuals. Caffeine did not affect sweating responses during exercise in the heat.
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Affiliation(s)
- Lindsey A Hunt
- Thermal Ergonomics Laboratory, Faculty of Medicine and Health, Sydney School of Health Sciences, The University of Sydney, Camperdown, New South Wales, Australia
| | - Lily Hospers
- Thermal Ergonomics Laboratory, Faculty of Medicine and Health, Sydney School of Health Sciences, The University of Sydney, Camperdown, New South Wales, Australia
| | - James W Smallcombe
- Thermal Ergonomics Laboratory, Faculty of Medicine and Health, Sydney School of Health Sciences, The University of Sydney, Camperdown, New South Wales, Australia
| | - Yorgi Mavros
- Thermal Ergonomics Laboratory, Faculty of Medicine and Health, Sydney School of Health Sciences, The University of Sydney, Camperdown, New South Wales, Australia.,Charles Perkins Centre, The University of Sydney, Camperdown, New South Wales, Australia
| | - Ollie Jay
- Thermal Ergonomics Laboratory, Faculty of Medicine and Health, Sydney School of Health Sciences, The University of Sydney, Camperdown, New South Wales, Australia.,Charles Perkins Centre, The University of Sydney, Camperdown, New South Wales, Australia
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Peel JS, McNarry MA, Heffernan SM, Nevola VR, Kilduff LP, Waldron M. The Effect of Dietary Supplements on Endurance Exercise Performance and Core Temperature in Hot Environments: A Meta-analysis and Meta-regression. Sports Med 2021; 51:2351-2371. [PMID: 34129223 PMCID: PMC8514372 DOI: 10.1007/s40279-021-01500-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/02/2021] [Indexed: 01/07/2023]
Abstract
BACKGROUND The ergogenic effects of dietary supplements on endurance exercise performance are well-established; however, their efficacy in hot environmental conditions has not been systematically evaluated. OBJECTIVES (1) To meta-analyse studies investigating the effects of selected dietary supplements on endurance performance and core temperature responses in the heat. Supplements were included if they were deemed to: (a) have a strong evidence base for 'directly' improving thermoneutral endurance performance, based on current position statements, or (b) have a proposed mechanism of action that related to modifiable factors associated with thermal balance. (2) To conduct meta-regressions to evaluate the moderating effect of selected variables on endurance performance and core temperature responses in the heat following dietary supplementation. METHODS A search was performed using various databases in May 2020. After screening, 25 peer-reviewed articles were identified for inclusion, across three separate meta-analyses: (1) exercise performance; (2) end core temperature; (3) submaximal core temperature. The moderating effect of several variables were assessed via sub-analysis and meta-regression. RESULTS Overall, dietary supplementation had a trivial significant positive effect on exercise performance (Hedges' g = 0.18, 95% CI 0.007-0.352, P = 0.042), a trivial non-significant positive effect on submaximal core temperature (Hedges' g = 0.18, 95% CI - 0.021 to 0.379, P = 0.080) and a small non-significant positive effect on end core temperature (Hedges' g = 0.20, 95% CI - 0.041 to 0.439, P = 0.104) in the heat. There was a non-significant effect of individual supplements on exercise performance (P = 0.973) and submaximal core temperature (P = 0.599). However, end core temperature was significantly affected by supplement type (P = 0.003), which was attributable to caffeine's large significant positive effect (n = 8; Hedges' g = 0.82, 95% CI 0.433-1.202, P < 0.001) and taurine's medium significant negative effect (n = 1; Hedges' g = - 0.96, 95% CI - 1.855 to - 0.069, P = 0.035). CONCLUSION Supplements such as caffeine and nitrates do not enhance endurance performance in the heat, with caffeine also increasing core temperature responses. Some amino acids might offer the greatest performance benefits in the heat. Exercising in the heat negatively affected the efficacy of many dietary supplements, indicating that further research is needed and current guidelines for performance in hot environments likely require revision.
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Affiliation(s)
- Jennifer S Peel
- A-STEM Centre, College of Engineering, Swansea University, Swansea, UK.
| | - Melitta A McNarry
- A-STEM Centre, College of Engineering, Swansea University, Swansea, UK
| | - Shane M Heffernan
- A-STEM Centre, College of Engineering, Swansea University, Swansea, UK
| | - Venturino R Nevola
- A-STEM Centre, College of Engineering, Swansea University, Swansea, UK
- Defence Science and Technology Laboratory (Dstl), Fareham, Hampshire, UK
| | - Liam P Kilduff
- A-STEM Centre, College of Engineering, Swansea University, Swansea, UK
- Welsh Institute of Performance Science, Swansea University, Swansea, UK
| | - Mark Waldron
- A-STEM Centre, College of Engineering, Swansea University, Swansea, UK
- Welsh Institute of Performance Science, Swansea University, Swansea, UK
- School of Science and Technology, University of New England, Armidale, NSW, Australia
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10
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Fujii N, Fujimoto T, Yinhang C, Dobashi K, Matsutake R, Amano T, Watanabe K, Nishiyasu T. Caffeine Exacerbates Hyperventilation and Reductions in Cerebral Blood Flow in Physically Fit Men Exercising in the Heat. Med Sci Sports Exerc 2021; 53:845-852. [PMID: 33044440 DOI: 10.1249/mss.0000000000002537] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
INTRODUCTION Caffeine is an exercise performance enhancer widely used by individuals engaged in training or competition under heat-stressed conditions. Caffeine ingestion during exercise in the heat is believed to be safe because it does not greatly affect body temperature responses, heart rate, or body fluid status. However, it remains unknown whether caffeine affects hyperthermia-induced hyperventilation or reductions in the cerebral blood flow index. We tested the hypothesis that under conditions inducing severe hyperthermia, caffeine exacerbates hyperthermia-induced hyperventilation and reduces the cerebral blood flow index during exercise. METHODS Using a randomized, single-blind, crossover design, 12 physically active healthy young men (23 ± 2 yr) consumed a moderate dose of caffeine (5 mg·kg-1) or placebo in the heat (37°C). Approximately 60 min after the ingestion, they cycled for ~45 min at a workload equal to ~55% of their predetermined peak oxygen uptake (moderate intensity) until their core temperature increased to 2.0°C above its preexercise baseline level. RESULTS In both trials, ventilation increased and the cerebral blood flow index assessed by middle cerebral artery mean blood velocity decreased as core temperature rose during exercise (P < 0.05), indicating that hyperthermia-induced hyperventilation and lowering of the cerebral blood flow occurred. When core temperature was elevated by 1.5°C or more (P < 0.05), ventilation was higher and the cerebral blood flow was lower throughout the caffeine trial than the placebo trial (P < 0.05). CONCLUSIONS A moderate dose of caffeine exacerbates hyperthermia-induced hyperventilation and reductions in the cerebral blood flow index during exercise in the heat with severe hyperthermia.
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Affiliation(s)
- Naoto Fujii
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, JAPAN
| | | | | | - Kohei Dobashi
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, JAPAN
| | - Ryoko Matsutake
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, JAPAN
| | - Tatsuro Amano
- Laboratory for Exercise and Environmental Physiology, Faculty of Education, Niigata University, Niigata, JAPAN
| | - Koichi Watanabe
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, JAPAN
| | - Takeshi Nishiyasu
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, JAPAN
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11
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Guest NS, VanDusseldorp TA, Nelson MT, Grgic J, Schoenfeld BJ, Jenkins NDM, Arent SM, Antonio J, Stout JR, Trexler ET, Smith-Ryan AE, Goldstein ER, Kalman DS, Campbell BI. International society of sports nutrition position stand: caffeine and exercise performance. J Int Soc Sports Nutr 2021; 18:1. [PMID: 33388079 PMCID: PMC7777221 DOI: 10.1186/s12970-020-00383-4] [Citation(s) in RCA: 193] [Impact Index Per Article: 64.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 10/31/2020] [Indexed: 12/13/2022] Open
Abstract
Following critical evaluation of the available literature to date, The International Society of Sports Nutrition (ISSN) position regarding caffeine intake is as follows: 1. Supplementation with caffeine has been shown to acutely enhance various aspects of exercise performance in many but not all studies. Small to moderate benefits of caffeine use include, but are not limited to: muscular endurance, movement velocity and muscular strength, sprinting, jumping, and throwing performance, as well as a wide range of aerobic and anaerobic sport-specific actions. 2. Aerobic endurance appears to be the form of exercise with the most consistent moderate-to-large benefits from caffeine use, although the magnitude of its effects differs between individuals. 3. Caffeine has consistently been shown to improve exercise performance when consumed in doses of 3-6 mg/kg body mass. Minimal effective doses of caffeine currently remain unclear but they may be as low as 2 mg/kg body mass. Very high doses of caffeine (e.g. 9 mg/kg) are associated with a high incidence of side-effects and do not seem to be required to elicit an ergogenic effect. 4. The most commonly used timing of caffeine supplementation is 60 min pre-exercise. Optimal timing of caffeine ingestion likely depends on the source of caffeine. For example, as compared to caffeine capsules, caffeine chewing gums may require a shorter waiting time from consumption to the start of the exercise session. 5. Caffeine appears to improve physical performance in both trained and untrained individuals. 6. Inter-individual differences in sport and exercise performance as well as adverse effects on sleep or feelings of anxiety following caffeine ingestion may be attributed to genetic variation associated with caffeine metabolism, and physical and psychological response. Other factors such as habitual caffeine intake also may play a role in between-individual response variation. 7. Caffeine has been shown to be ergogenic for cognitive function, including attention and vigilance, in most individuals. 8. Caffeine may improve cognitive and physical performance in some individuals under conditions of sleep deprivation. 9. The use of caffeine in conjunction with endurance exercise in the heat and at altitude is well supported when dosages range from 3 to 6 mg/kg and 4-6 mg/kg, respectively. 10. Alternative sources of caffeine such as caffeinated chewing gum, mouth rinses, energy gels and chews have been shown to improve performance, primarily in aerobic exercise. 11. Energy drinks and pre-workout supplements containing caffeine have been demonstrated to enhance both anaerobic and aerobic performance.
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Affiliation(s)
- Nanci S Guest
- Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, 1 King's College Circle, Room 5326A, Toronto, ON, M5S 1A8, Canada.
| | - Trisha A VanDusseldorp
- Department of Exercise Science and Sport Management, Kennesaw State University, Kennesaw, GA, 30144, USA
| | | | - Jozo Grgic
- Institute for Health and Sport (IHES), Victoria University, Melbourne, Australia
| | - Brad J Schoenfeld
- Department of Health Sciences, CUNY Lehman College, Bronx, NY, 10468, USA
| | - Nathaniel D M Jenkins
- Department of Health and Human Physiology, University of Iowa, Iowa City, IA, 52240, USA
| | - Shawn M Arent
- Department of Exercise Science, Arnold School of Public Health, University of South Carolina, Colombia, SC, 29208, USA
- School of Social and Health Sciences, Leeds Trinity University, Leeds, UK
| | - Jose Antonio
- Exercise and Sport Science, Nova Southeastern University, Davie, FL, 33314, USA
| | - Jeffrey R Stout
- Institue of Exercise Physiology and Rehabilitation Science, University of Central Florida, Orlando, FL, 32816, USA
| | | | - Abbie E Smith-Ryan
- Department of Exercise and Sport Science, Applied Physiology Laboratory, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Erica R Goldstein
- Institue of Exercise Physiology and Rehabilitation Science, University of Central Florida, Orlando, FL, 32816, USA
| | - Douglas S Kalman
- Nutrion Department, College of Osteopathic Medicine, Nova Southeastern University, Fort Lauderdale, FL, 33314, USA
- Scientific Affairs. Nutrasource, Guelph, ON, Canada
| | - Bill I Campbell
- Performance & Physique Enhancement Laboratory, University of South Florida, Tampa, FL, 33612, USA
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12
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Ruiz-Moreno C, Gutiérrez-Hellín J, Amaro-Gahete FJ, González-García J, Giráldez-Costas V, Pérez-García V, Del Coso J. Caffeine increases whole-body fat oxidation during 1 h of cycling at Fatmax. Eur J Nutr 2020; 60:2077-2085. [PMID: 33025051 DOI: 10.1007/s00394-020-02393-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 09/21/2020] [Indexed: 12/21/2022]
Abstract
PURPOSE The ergogenic effect of caffeine on exercise of maximum intensity has been well established. However, there is controversy regarding the effect of caffeine on shifting substrate oxidation at submaximal exercise. The aim of this study was to investigate the effect of acute caffeine ingestion on whole-body substrate oxidation during 1 h of cycling at the intensity that elicits maximal fat oxidation (Fatmax). METHODS In a double-blind, randomized, and counterbalanced experiment, 12 healthy participants (VO2max = 50.7 ± 12.1 mL/kg/min) performed two acute experimental trials after ingesting either caffeine (3 mg/kg) or a placebo (cellulose). The trials consisted of 1 h of continuous cycling at Fatmax. Energy expenditure, fat oxidation rate, and carbohydrate oxidation rate were continuously measured by indirect calorimetry. RESULTS In comparison to the placebo, caffeine increased the amount of fat oxidized during the trial (19.4 ± 7.7 vs 24.7 ± 9.6 g, respectively; P = 0.04) and decreased the amount of carbohydrate oxidized (94.6 ± 30.9 vs 73.8 ± 32.4 g; P = 0.01) and the mean self-perception of fatigue (Borg scale = 11 ± 2 vs 10 ± 2 arbitrary units; P = 0.05). In contrast, caffeine did not modify total energy expenditure (placebo = 543 ± 175; caffeine = 559 ± 170 kcal; P = 0.60) or mean heart rate (125 ± 13 and 127 ± 9 beats/min; P = 0.30) during exercise. Before exercise, caffeine increased systolic and diastolic blood pressure whilst it increased the feelings of nervousness and vigour after exercise (P < 0.05). CONCLUSION These results suggest that a moderate dose of caffeine (3 mg/kg) increases the amount of fat oxidized during 1 h of cycling at Fatmax. Thus, caffeine might be used as an effective strategy to enhance body fat utilization during submaximal exercise. The occurrence of several side effects should be taken into account when using caffeine to reduce body fat in populations with hypertension or high sensitivity to caffeine.
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Affiliation(s)
- Carlos Ruiz-Moreno
- Exercise Physiology Laboratory, Camilo José Cela University, Madrid, Spain
| | | | | | | | - Verónica Giráldez-Costas
- Exercise Physiology Laboratory, Camilo José Cela University, Madrid, Spain.,Department of Physical Education, Sport and Human Movement, Autonomus University of Madrid, Madrid, Spain
| | | | - Juan Del Coso
- Centre for Sport Studies, Rey Juan Carlos University, Camino del Molino, s/n, 28943, Fuenlabrada, Spain.
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13
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Cassol G, Godinho DB, de Zorzi VN, Farinha JB, Della-Pace ID, de Carvalho Gonçalves M, Oliveira MS, Furian AF, Fighera MR, Royes LFF. Potential therapeutic implications of ergogenic compounds on pathophysiology induced by traumatic brain injury: A narrative review. Life Sci 2019; 233:116684. [DOI: 10.1016/j.lfs.2019.116684] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Accepted: 07/22/2019] [Indexed: 12/19/2022]
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14
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Gutiérrez-Hellín J, Del Coso J. Effects of p-Synephrine and Caffeine Ingestion on Substrate Oxidation during Exercise. Med Sci Sports Exerc 2019; 50:1899-1906. [PMID: 29727404 DOI: 10.1249/mss.0000000000001653] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
PURPOSE Caffeine and p-synephrine are substances usually included in commercially available products for weight loss because of their purported thermogenic effects. However, scientific information is lacking about the effects of combining these substances on substrate oxidation during exercise. The purpose of this investigation was to determine the isolated and combined effects of p-synephrine and caffeine on fat oxidation rate during exercise. METHODS In a double-blind randomized experiment, 13 healthy subjects participated in four experimental trials after the ingestion of a capsule containing a placebo, 3 mg·kg of caffeine, 3 mg·kg of p-synephrine, or the combination of these doses of caffeine and p-synephrine. Energy expenditure and substrate oxidation rates were measured by indirect calorimetry during a cycle ergometer ramp test from 30% to 90% of V˙O2max. RESULTS In comparison with the placebo, the ingestion of caffeine, p-synephrine, or p-synephrine + caffeine did not alter total energy expenditure or heart rate during the whole exercise test. However, the ingestion of caffeine (0.44 ± 0.15 g·min, P = 0.03), p-synephrine (0.43 ± 0.19 g·min, P < 0.01), and p-synephrine + caffeine (0.45 ± 0.15 g·min, P = 0.02) increased the maximal rate of fat oxidation during exercise when compared with the placebo (0.30 ± 0.12 g·min). The exercise intensity that elicited maximal fat oxidation was similar in all trials (~46.2% ± 10.2% of V˙O2max). CONCLUSION Caffeine, p-synephrine, and p-synephrine + caffeine increased the maximal rate of fat oxidation during exercise compared with a placebo, without modifying energy expenditure or heart rate. However, the coingestion of p-synephrine and caffeine did not present an additive effect to further increase fat oxidation during exercise.
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15
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Increased Rate of Heat Storage, and No Performance Benefits, With Caffeine Ingestion Before a 10-km Run in Hot, Humid Conditions. Int J Sports Physiol Perform 2019; 14:196-202. [PMID: 30039995 DOI: 10.1123/ijspp.2018-0263] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
PURPOSE Although the effect of caffeine in thermoneutral or cool environmental conditions has generally shown performance benefits, its efficacy in hot, humid conditions is not as well known. The purpose of this study was to further examine the effect of caffeine ingestion on endurance running performance in the heat. METHODS Ten trained endurance runners (6 males; mean [SD] age = 26 [9] y, height = 176.7 [5.1] cm, and mass = 72.1 [8.7] kg) came to the lab for 4 visits. The first was a VO2max test to determine cardiorespiratory fitness; the final 3 visits were 10-km runs in an environmental chamber at 30.6°C and 50% relative humidity under different conditions: 3 mg·kg-1 body mass (low caffeine dosage), 6 mg·kg-1 (moderate caffeine dosage), and a placebo. Repeated-measures analyses of variance were used to determine the effect of condition on the 10-km time, heart rate, core temperature, rating of perceived exertion, and thermal sensation. RESULTS There was no difference in the 10-km time between the placebo (53.2 [8.0] min), 3-mg·kg-1 (53.4 [8.4]), and 6-mg·kg-1 (52.7 [8.2]) conditions (P = .575, ηp2=.060 ). There was not a main effect of average heart rate (P = .406, ηp2=.107 ), rating of perceived exertion (P = .151, ηp2=.189 ), or thermal sensation (P = .286, ηp2=.130 ). There was a significant interaction for core temperature (P = .025, ηp2=.170 ); the moderate-dosage caffeine condition showed a higher rate of rise in core temperature (0.26 [0.08] °C·km-1 vs 0.20 [0.06] and 0.19 [0.10] °C·km-1 in the low-caffeine and placebo conditions, respectively). CONCLUSION The results support previous research showing a thermogenic effect of caffeine, as the moderate-dosage condition led to a greater rate of heat storage and no performance benefits.
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16
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Are There Non-Responders to the Ergogenic Effects of Caffeine Ingestion on Exercise Performance? Nutrients 2018; 10:nu10111736. [PMID: 30424511 PMCID: PMC6267019 DOI: 10.3390/nu10111736] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Accepted: 11/09/2018] [Indexed: 12/22/2022] Open
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Southward K, Rutherfurd-Markwick KJ, Ali A. The Effect of Acute Caffeine Ingestion on Endurance Performance: A Systematic Review and Meta-Analysis. Sports Med 2018; 48:1913-1928. [PMID: 29876876 DOI: 10.1007/s40279-018-0939-8] [Citation(s) in RCA: 111] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND Caffeine is a widely used ergogenic aid with most research suggesting it confers the greatest effects during endurance activities. Despite the growing body of literature around the use of caffeine as an ergogenic aid, there are few recent meta-analyses that quantitatively assess the effect of caffeine on endurance exercise. OBJECTIVES To summarise studies that have investigated the ergogenic effects of caffeine on endurance time-trial performance and to quantitatively analyse the results of these studies to gain a better understanding of the magnitude of the ergogenic effect of caffeine on endurance time-trial performance. METHODS A systematic review was carried out on randomised placebo-controlled studies investigating the effects of caffeine on endurance performance and a meta-analysis was conducted to determine the ergogenic effect of caffeine on endurance time-trial performance. RESULTS Forty-six studies met the inclusion criteria and were included in the meta-analysis. Caffeine has a small but evident effect on endurance performance when taken in moderate doses (3-6 mg/kg) as well as an overall improvement following caffeine compared to placebo in mean power output (3.03 ± 3.07%; effect size = 0.23 ± 0.15) and time-trial completion time (2.22 ± 2.59%; effect size = 0.41 ± 0.2). However, differences in responses to caffeine ingestion have been shown, with two studies reporting slower time-trial performance, while five studies reported lower mean power output during the time-trial. CONCLUSION Caffeine can be used effectively as an ergogenic aid when taken in moderate doses, such as during sports when a small increase in endurance performance can lead to significant differences in placements as athletes are often separated by small margins.
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Affiliation(s)
- Kyle Southward
- School of Sport, Exercise and Nutrition, Massey University, North Shore Mail Centre, Private Bag 102 904, Auckland, 0745, New Zealand
| | - Kay J Rutherfurd-Markwick
- School of Health Sciences, Massey University, Auckland, New Zealand.,Centre for Metabolic Health Research, Massey University, Auckland, New Zealand
| | - Ajmol Ali
- School of Sport, Exercise and Nutrition, Massey University, North Shore Mail Centre, Private Bag 102 904, Auckland, 0745, New Zealand. .,Centre for Metabolic Health Research, Massey University, Auckland, New Zealand.
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Southward K, Rutherfurd-Markwick K, Badenhorst C, Ali A. The Role of Genetics in Moderating the Inter-Individual Differences in the Ergogenicity of Caffeine. Nutrients 2018; 10:E1352. [PMID: 30248915 PMCID: PMC6213712 DOI: 10.3390/nu10101352] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Revised: 09/10/2018] [Accepted: 09/17/2018] [Indexed: 12/17/2022] Open
Abstract
Caffeine use is widespread among athletes following its removal from the World Anti-Doping Agency banned list, with approximately 75% of competitive athletes using caffeine. While literature supports that caffeine has a small positive ergogenic effect for most forms of sports and exercise, there exists a significant amount of inter-individual difference in the response to caffeine ingestion and the subsequent effect on exercise performance. In this narrative review, we discuss some of the potential mechanisms and focus on the role that genetics has in these differences. CYP1A2 and ADORA2A are two of the genes which are thought to have the largest impact on the ergogenicity of caffeine. CYP1A2 is responsible for the majority of the metabolism of caffeine, and ADORA2A has been linked to caffeine-induced anxiety. The effects of CYP1A2 and ADORA2A genes on responses to caffeine will be discussed in detail and an overview of the current literature will be presented. The role of these two genes may explain a large portion of the inter-individual variance reported by studies following caffeine ingestion. Elucidating the extent to which these genes moderate responses to caffeine during exercise will ensure caffeine supplementation programs can be tailored to individual athletes in order to maximize the potential ergogenic effect.
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Affiliation(s)
- Kyle Southward
- School of Sport, Exercise and Nutrition, Massey University, North Shore Mail Centre, Private Bag 102 904, Auckland 0745, New Zealand.
| | - Kay Rutherfurd-Markwick
- School of Health Sciences, Massey University, Auckland 0745, New Zealand.
- Centre for Metabolic Health Research, Massey University, Auckland 0745, New Zealand.
| | - Claire Badenhorst
- School of Sport, Exercise and Nutrition, Massey University, North Shore Mail Centre, Private Bag 102 904, Auckland 0745, New Zealand.
- Centre for Metabolic Health Research, Massey University, Auckland 0745, New Zealand.
| | - Ajmol Ali
- School of Sport, Exercise and Nutrition, Massey University, North Shore Mail Centre, Private Bag 102 904, Auckland 0745, New Zealand.
- Centre for Metabolic Health Research, Massey University, Auckland 0745, New Zealand.
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Southward K, Rutherfurd-Markwick KJ, Ali A. Correction to: The Effect of Acute Caffeine Ingestion on Endurance Performance: A Systematic Review and Meta-Analysis. Sports Med 2018; 48:2425-2441. [DOI: 10.1007/s40279-018-0967-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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