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Magaña MA, Gorini Pereira FL, Kuennen MR, Lutz CJ, Almond DG, Lira AA, Apilado AJ, Kim JK, Boyer WR, Gillum TL. Caffeine has no effect on submaximal running in hypoxia in low caffeine consuming males and females. J Sports Med Phys Fitness 2024; 64:863-870. [PMID: 38842372 DOI: 10.23736/s0022-4707.24.15840-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2024]
Abstract
BACKGROUND Exposure to hypoxia immediately challenges a variety of physiologic systems that limit exercise capacity. Under normoxia, caffeine (CAFF) increases ventilation and subsequent oxygenation of hemoglobin (SpO2) and skeletal muscle (SmO2). CAFF improves exercise performance at altitude. However, little attention has been given to submaximal exercise in hypoxia, particularly regarding low CAFF consumers and female participants. The aim of this study was to determine the effect of CAFF on pulmonary, metabolic, and perceptual variables in response to submaximal running in hypoxia in low CAFF consuming males and females. METHODS In a double blinded, counterbalanced design, 14 (6 females) individuals (24.1±5.1 years; VO2max: 40.6±5.6 mL × kg-1 × min-1; 20.8±8.0% body fat), who habitually consumed ≤150 mg/day of CAFF performed treadmill running at workloads of 25%, 40%, 60%, and 75% of sea level VO2max in normobaric hypoxia (FIO2=0.15) on two separate occasions: 1) 60 minutes after 6 mg/kg of CAFF; or 2) placebo. RESULTS CAFF had no effect on any variable measured. Specifically, VE (condition: P=0.12; interaction: P=0.19), VT (condition: P=0.16; interaction: P=0.57), and Ve:VO2 (condition: P=0.07; interaction: P=0.69) were similar between groups. Further, CAFF had no effect on relative VO2 (condition: P=0.84; interaction: P=0.95), HR (condition: P=0.28; interaction: P=0.35), SmO2 (condition: P=0.66; interaction: P=0.82), or SpO2 (condition: P=0.16; interaction: P=0.97). Finally, rating of perceived exertion (RPE; P=0.92) and acute mountain sickness scores (P=0.29) were similar across conditions. CONCLUSIONS These data demonstrate that CAFF provides no physiologic advantage to submaximal exercise in acute, normobaric hypoxia with low CAFF consuming males and females.
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Affiliation(s)
- Marc A Magaña
- Department of Kinesiology, California Baptist University, Riverside, CA, USA
- Department of Health, Human Performance, and Recreation, Baylor University, Waco, TX, USA
| | | | - Matthew R Kuennen
- Department of Exercise Science, High Point University, High Point, NC, USA
| | - Christen J Lutz
- Department of Kinesiology, California Baptist University, Riverside, CA, USA
| | - Danee G Almond
- Department of Kinesiology, California Baptist University, Riverside, CA, USA
| | - Albert A Lira
- Department of Kinesiology, California Baptist University, Riverside, CA, USA
| | - Alvin J Apilado
- Department of Kinesiology, California Baptist University, Riverside, CA, USA
| | - Jong-Kyung Kim
- Department of Kinesiology, California Baptist University, Riverside, CA, USA
| | - William R Boyer
- Department of Kinesiology, California Baptist University, Riverside, CA, USA
| | - Trevor L Gillum
- Department of Kinesiology, California Baptist University, Riverside, CA, USA -
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Cao Y, He W, Ding L, Lei TH, Schlader Z, Mundel T, Wang R, Guo L, Liu J, Girard O. Dose-response effects of caffeine during repeated cycling sprints in normobaric hypoxia to exhaustion. Eur J Appl Physiol 2024:10.1007/s00421-024-05576-2. [PMID: 39179881 DOI: 10.1007/s00421-024-05576-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2024] [Accepted: 08/13/2024] [Indexed: 08/26/2024]
Abstract
PURPOSE With limited studies exploring the dose-response of caffeine consumption on repeated sprint ability in hypoxia, this study aimed to determine the optimal caffeine dose (low, moderate or high) during repeated sprints in hypoxia to exhaustion. METHODS On separate visits, twelve active males randomly performed four experimental trials in normobaric hypoxia (inspired oxygen fraction: 16.5 ± 0.2%). Participants ingested placebo (PLA) or caffeine capsules (3, 6 or 9 mg/kg or LOW, MOD and HIGH, respectively) 1 h before exercise and then underwent a repeated cycling sprint test (10 s sprint/20 s active recovery) to exhaustion. Total sprint number and work done, peak and mean power output, blood lactate concentration, cardiorespiratory and perceptual responses were recorded. RESULTS Total sprint number was greater in MOD and HIGH compared to PLA (20 ± 7 and 18 ± 8 vs. 13 ± 4; all P < 0.05), with MOD also higher than LOW (15 ± 6; P = 0.02). Total work done was greater in MOD (111 ± 40 kJ) and HIGH (100 ± 35 kJ) compared to LOW (83 ± 29 kJ) and PLA (76 ± 25 kJ) (all P < 0.05). However, there were no significant differences in total sprint number or total work done between MOD and HIGH (all P > 0.05). Blood lactate concentration was higher in both MOD and HIGH compared to PLA (all P < 0.05). However, peak and mean power outputs, fatigue index, and ratings of perceived exertion did not differ across different caffeine dosages (all P > 0.05). CONCLUSION A moderate dose of caffeine (6 mg/kg) is the optimal amount for enhancing repeated cycling sprint ability when compared to low and high doses in moderate normobaric hypoxia.
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Affiliation(s)
- Yinhang Cao
- School of Athletic Performance, Shanghai University of Sport, Shanghai, People's Republic of China
| | - Wei He
- School of Athletic Performance, Shanghai University of Sport, Shanghai, People's Republic of China
| | - Li Ding
- School of Athletic Performance, Shanghai University of Sport, Shanghai, People's Republic of China
| | - Tze-Huan Lei
- Occupational Safety and Health Group (OSHG), College of Safety Science and Engineering, Xi'an University of Science and Technology, Xi'an, People's Republic of China
| | - Zachary Schlader
- Department of Kinesiology, Indiana University School of Public Health, Bloomington, IN, USA
| | - Toby Mundel
- Department of Kinesiology, Brock University, St. Catharines, ON, Canada
| | - Ran Wang
- School of Athletic Performance, Shanghai University of Sport, Shanghai, People's Republic of China
| | - Li Guo
- School of Exercise and Health, Shanghai University of Sport, Shanghai, People's Republic of China
| | - Jue Liu
- Department of Rehabilitation Medicine, Huashan Hospital, Fudan University, Shanghai, 200040, People's Republic of China.
| | - Olivier Girard
- School of Human Sciences (Exercise and Sport Science), The University of Western Australia, Perth, Australia
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Lei TH, Qin Q, Girard O, Mündel T, Wang R, Guo L, Cao Y. Caffeine intake enhances peak oxygen uptake and performance during high-intensity cycling exercise in moderate hypoxia. Eur J Appl Physiol 2024; 124:537-549. [PMID: 37608124 DOI: 10.1007/s00421-023-05295-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Accepted: 08/07/2023] [Indexed: 08/24/2023]
Abstract
PURPOSE We investigated whether caffeine consumption can enhance peak oxygen uptake ([Formula: see text]) by increasing peak ventilation during an incremental cycling test, and subsequently enhance time to exhaustion (TTE) during high-intensity cycling exercise in moderate normobaric hypoxia. METHODS We conducted a double-blind, placebo cross-over design study. Sixteen recreational male endurance athletes (age: 20 ± 2 years, [Formula: see text]: 55.6 ± 3.6 ml/kg/min, peak power output: 318 ± 40 W) underwent an incremental cycling test and a TTE test at 80% [Formula: see text] (derived from the placebo trial) in moderate normobaric hypoxia (fraction of inspired O2: 15.3 ± 0.2% corresponding to a simulated altitude of ~ 2500 m) after consuming either a moderate dose of caffeine (6 mg/kg) or a placebo. RESULTS Caffeine consumption resulted in a higher peak ventilation [159 ± 21 vs. 150 ± 26 L/min; P < 0.05; effect size (ES) = 0.31]. [Formula: see text] (3.58 ± 0.44 vs. 3.47 ± 0.47 L/min; P < 0.01; ES = 0.44) and peak power output (308 ± 44 vs. 302 ± 44 W; P = 0.02, ES = 0.14) were higher following caffeine consumption than during the placebo trial. During the TTE test, caffeine consumption enhanced minute ventilation (P = 0.02; ES = 0.28) and extended the TTE (426 ± 74 vs. 358 ± 75 s; P < 0.01, ES = 0.91) compared to the placebo trial. There was a positive correlation between the percent increase of [Formula: see text] following caffeine consumption and the percent increase in TTE (r = 0.49, P < 0.05). CONCLUSION Moderate caffeine consumption stimulates breathing and aerobic metabolism, resulting in improved performance during incremental and high-intensity endurance exercises in moderate normobaric hypoxia.
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Affiliation(s)
- Tze-Huan Lei
- College of Physical Education, Hubei Normal University, Huangshi, China
| | - Qiyang Qin
- School of Athletic Performance, Shanghai University of Sport, Shanghai, 200438, China
| | - Olivier Girard
- School of Human Sciences (Exercise and Sport Science), The University of Western Australia, Perth, Australia
| | - Toby Mündel
- Department of Kinesiology, Brock University, St. Catharines, Canada
| | - Ran Wang
- School of Athletic Performance, Shanghai University of Sport, Shanghai, 200438, China
| | - Li Guo
- School of Exercise and Health, Shanghai University of Sport, Shanghai, China
| | - Yinhang Cao
- School of Athletic Performance, Shanghai University of Sport, Shanghai, 200438, China.
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Fenne KT, Clauss M, Schäfer Olstad D, Johansen EI, Jensen J. An Acute Bout of Endurance Exercise Does Not Prevent the Inhibitory Effect of Caffeine on Glucose Tolerance the following Morning. Nutrients 2023; 15:nu15081941. [PMID: 37111160 PMCID: PMC10143402 DOI: 10.3390/nu15081941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 03/29/2023] [Accepted: 04/13/2023] [Indexed: 04/29/2023] Open
Abstract
Caffeine reduces glucose tolerance, whereas exercise training improves glucose homeostasis. The aim of the present study was to investigate the effect of caffeine on glucose tolerance the morning after an acute bout of aerobic exercise. Methods: The study had a 2 × 2 factorial design. Oral glucose tolerance tests (OGTT) were performed after overnight fasting with/without caffeine and with/without exercise the evening before. Eight healthy young active males were included (Age 25.5 ± 1.5 years; 83.9 ± 9.0 kg; VO2max: 54.3 ± 7.0 mL·kg-1·min-1). The exercise session consisted of 30 min cycling at 71% of VO2max followed by four 5 min intervals at 84% with 3 min of cycling at 40% of VO2max between intervals. The exercise was performed at 17:00 h. Energy expenditure at each session was ~976 kcal. Lactate increased to ~8 mM during the exercise sessions. Participants arrived at the laboratory the following morning at 7.00 AM after an overnight fast. Resting blood samples were taken before blood pressure and heart rate variability (HRV) were measured. Caffeine (3 mg/kg bodyweight) or placebo (similar taste/flavor) was ingested, and blood samples, blood pressure and HRV were measured after 30 min. Next, the OGTTs were initiated (75 g glucose dissolved in 3 dL water) and blood was sampled. Blood pressure and HRV were measured during the OGTT. Caffeine increased the area under curve (AUC) for glucose independently of whether exercise was done the evening before (p = 0.03; Two-way ANOVA; Interaction: p = 0.835). Caffeine did not significantly increase AUC for C-peptides compared to placebo (p = 0.096), and C-peptide response was not influenced by exercise. The acute bout of exercise did not significantly improve glucose tolerance the following morning. Diastolic blood pressure during the OGTT was slightly higher after intake of caffeine, independent of whether exercise was performed the evening before or not. Neither caffeine nor exercise the evening before significantly influenced HRV. In conclusion, caffeine reduced glucose tolerance independently of whether endurance exercise was performed the evening before. The low dose of caffeine did not influence heart rate variability but increased diastolic blood pressure slightly.
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Affiliation(s)
- Karoline T Fenne
- Department of Physical Performance, Norwegian School of Sport Sciences, P.O. Box 4014, Ullevål Stadion, 0806 Oslo, Norway
| | - Matthieu Clauss
- Department of Physical Performance, Norwegian School of Sport Sciences, P.O. Box 4014, Ullevål Stadion, 0806 Oslo, Norway
| | | | - Egil I Johansen
- Department of Physical Performance, Norwegian School of Sport Sciences, P.O. Box 4014, Ullevål Stadion, 0806 Oslo, Norway
| | - Jørgen Jensen
- Department of Physical Performance, Norwegian School of Sport Sciences, P.O. Box 4014, Ullevål Stadion, 0806 Oslo, Norway
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Stadheim HK, Stensrud T, Brage S, Jensen J. Caffeine Increases Exercise Performance, Maximal Oxygen Uptake, and Oxygen Deficit in Elite Male Endurance Athletes. Med Sci Sports Exerc 2021; 53:2264-2273. [PMID: 34033621 DOI: 10.1249/mss.0000000000002704] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE The aims of the present study were to test the hypothesis that caffeine increases maximal oxygen uptake (V˙O2max) and to characterize the physiological mechanisms underpinning improved high-intensity endurance capacity. METHODS Twenty-three elite endurance-trained male athletes were tested twice with and twice without caffeine (four tests) in a randomized, double-blinded, and placebo-controlled study with crossover design. Caffeine (4.5 mg·kg-1) or placebo was consumed 45 min before standardized warm-up. Time to exhaustion during an incremental test (running 10.5° incline, start speed 10.0 km·h-1, and 0.5 km·h-1 increase in speed every 30 s) determined performance. Oxygen uptake was measured continuously to determine V˙O2max and O2 deficit was calculated. RESULTS Caffeine increased time to exhaustion from 355 ± 41 to 375 ± 41 s (Δ19.4 ± 16.5 s; P < 0.001). Importantly, caffeine increased V˙O2max from 75.8 ± 5.6 to 76.7 ± 6.0 mL·kg-1·min-1 (Δ 0.9 ± 1.7 mL·kg-1·min-1; P < 0.003). Caffeine increased maximal heart rate (HRpeak) and ventilation (VEpeak). Caffeine increased O2 deficit from 63.1 ± 18.2 to 69.5 ± 17.5 mL·kg-1 (P < 0.02) and blood lactate compared with placebo. The increase in time to exhaustion after caffeine ingestion was reduced to 11.7 s after adjustment for the increase in V˙O2max. Caffeine did not significantly increase V˙O2max after adjustment for VEpeak and HRpeak. Adjustment for O2 deficit and lactate explained 6.2 s of the caffeine-induced increase in time to exhaustion. The increase in V˙O2max, VE, HR, O2 deficit, and lactate explained 63% of the increased performance after caffeine intake. CONCLUSION Caffeine increased V˙O2max in elite athletes, which contributed to improvement in high-intensity endurance performance. Increases in O2 deficit and lactate also contributed to the caffeine-induced improvement in endurance performance.
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Affiliation(s)
- Hans Kristian Stadheim
- Department of Physical Performance, Norwegian School of Sport Sciences, Ullevål Stadion, NORWAY
| | - Trine Stensrud
- Department of Physical Performance, Norwegian School of Sport Sciences, Ullevål Stadion, NORWAY
| | - Søren Brage
- MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Institute of Metabolic Sciences, Cambridge Biomedical Campus, England, UNITED KINGDOM
| | - Jørgen Jensen
- Department of Physical Performance, Norwegian School of Sport Sciences, Ullevål Stadion, NORWAY
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Bosso H, Barbalho SM, de Alvares Goulart R, Otoboni AMMB. Green coffee: economic relevance and a systematic review of the effects on human health. Crit Rev Food Sci Nutr 2021; 63:394-410. [PMID: 34236263 DOI: 10.1080/10408398.2021.1948817] [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: 01/18/2023]
Abstract
Coffee is probably the most popular beverage after water and is an important component in diet and health since its consumption is high worldwide. Globally, it is the most relevant food commodity being just behind crude oil. Besides its pleasant flavor, it is an antioxidant source due to polyphenols, which are protective compounds against several diseases. This study aimed to evaluate the economic relevance and perform a systematic review of green coffee's effects on human health. Databases such as MEDLINE-PubMed, EMBASE, COCHRANE, and GOOGLE SCHOLAR were searched, and PRISMA guidelines were followed. Green coffee is considered a novel food product because consumers usually consume only roasted coffee. It can be marketed as such or as an extract. Due to the content of bioactive compounds, which are partially lost during the roasting process, the extracts are usually marketed concerning the potential regarding health effects. Green coffee can be used as dietary supplements, cosmetics, and pharmaceuticals, as a source of antioxidants. It can benefit human health, such as improvement in blood pressure, plasma lipids, and body weight (thus contributing to the improvement of risk components of Metabolic Syndrome). Moreover, benefits for cognitive functions may also be included.
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Affiliation(s)
- Henrique Bosso
- Medical school of São José do Rio Preto (FAMERP), Sao Jose do Rio Preto, Brazil
| | - Sandra Maria Barbalho
- Postgraduate Program in Structural and Functional Interactions in Rehabilitation - UNIMAR, Marília, SP, Brazil.,Department of Biochemistry and Pharmacology, School of Medicine, University of Marília (UNIMAR), Marília, São Paulo, Brazil.,School of Food and Technology of Marilia (FATEC), Marilia, São Paulo, Brazil
| | - Ricardo de Alvares Goulart
- Postgraduate Program in Structural and Functional Interactions in Rehabilitation - UNIMAR, Marília, SP, Brazil
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Hostrup M, Cairns SP, Bangsbo J. Muscle Ionic Shifts During Exercise: Implications for Fatigue and Exercise Performance. Compr Physiol 2021; 11:1895-1959. [PMID: 34190344 DOI: 10.1002/cphy.c190024] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Exercise causes major shifts in multiple ions (e.g., K+ , Na+ , H+ , lactate- , Ca2+ , and Cl- ) during muscle activity that contributes to development of muscle fatigue. Sarcolemmal processes can be impaired by the trans-sarcolemmal rundown of ion gradients for K+ , Na+ , and Ca2+ during fatiguing exercise, while changes in gradients for Cl- and Cl- conductance may exert either protective or detrimental effects on fatigue. Myocellular H+ accumulation may also contribute to fatigue development by lowering glycolytic rate and has been shown to act synergistically with inorganic phosphate (Pi) to compromise cross-bridge function. In addition, sarcoplasmic reticulum Ca2+ release function is severely affected by fatiguing exercise. Skeletal muscle has a multitude of ion transport systems that counter exercise-related ionic shifts of which the Na+ /K+ -ATPase is of major importance. Metabolic perturbations occurring during exercise can exacerbate trans-sarcolemmal ionic shifts, in particular for K+ and Cl- , respectively via metabolic regulation of the ATP-sensitive K+ channel (KATP ) and the chloride channel isoform 1 (ClC-1). Ion transport systems are highly adaptable to exercise training resulting in an enhanced ability to counter ionic disturbances to delay fatigue and improve exercise performance. In this article, we discuss (i) the ionic shifts occurring during exercise, (ii) the role of ion transport systems in skeletal muscle for ionic regulation, (iii) how ionic disturbances affect sarcolemmal processes and muscle fatigue, (iv) how metabolic perturbations exacerbate ionic shifts during exercise, and (v) how pharmacological manipulation and exercise training regulate ion transport systems to influence exercise performance in humans. © 2021 American Physiological Society. Compr Physiol 11:1895-1959, 2021.
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Affiliation(s)
- Morten Hostrup
- Section of Integrative Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Simeon Peter Cairns
- SPRINZ, School of Sport and Recreation, Auckland University of Technology, Auckland, New Zealand.,Health and Rehabilitation Research Institute, Auckland University of Technology, Auckland, New Zealand
| | - Jens Bangsbo
- Section of Integrative Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
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Benjamim CJR, Monteiro LRL, Pontes YMDM, Silva AAMD, Souza TKMD, Valenti VE, Garner DM, Cavalcante TCF. Caffeine slows heart rate autonomic recovery following strength exercise in healthy subjects. Rev Port Cardiol 2021; 40:399-406. [PMID: 34274079 DOI: 10.1016/j.repce.2020.07.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Accepted: 07/08/2020] [Indexed: 11/28/2022] Open
Abstract
INTRODUCTION AND OBJECTIVES Studies assessing the effects of caffeine (CAF) on the cardiovascular system have demonstrated that CAF can delay cardiac recovery following exercise. This study intended to assess the impact of CAF intake before physical exercise on heart rate variability (HRV) and cardiovascular parameters. METHODS This is a prospective, crossover, controlled clinical trial conducted at the University of Pernambuco, Petrolina, PE, Brazil. The experimental protocol was split into three stages with a minimum of 48 hours between them. Exercises intensity was standardized based on the one repetition maximum test (1RM), obtaining the load of each volunteer for the intensity of 75% of 1RM. In the second and third phases, the control protocols were applied and 300 mg caffeine was given 45 minutes before training. HRV indices were determined at the subsequent times: 0 to 5 minutes of rest (before) and during 30 minutes of recovery (Rec) (after exercise), divided into six intervals, each of 5 minutes. RESULTS The final sample involved 30 volunteers. CAF delayed HRV recovery after resistance exercise. In general, CAF impaired recovery of HRV after resistance exercise. Significant changes were observed in the RMSSD, SDNN, TINN, SD1, low frequency and high frequency indices between the control and CAF group. CONCLUSION CAF protocol delayed parasympathetic regulation of heart rhythm following exercise, slowing recovery of HR, blood pressure and HRV indices after exercise.
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Affiliation(s)
- Cicero Jonas R Benjamim
- Development, Nutrition, Phytotherapy and Hygiene Research Group, University of Pernambuco, Petrolina, PE, Brazil
| | - Larissa Raylane L Monteiro
- Nucleus of Studies in Physiological and Collective Sciences, School of Juazeiro do Norte, Juazeiro do Norte, CE, Brazil
| | - Yasmim M de Moraes Pontes
- Nucleus of Studies in Physiological and Collective Sciences, School of Juazeiro do Norte, Juazeiro do Norte, CE, Brazil
| | - Amanda A Marcelino da Silva
- Development, Nutrition, Phytotherapy and Hygiene Research Group, University of Pernambuco, Petrolina, PE, Brazil
| | - Thays K Marinho de Souza
- Development, Nutrition, Phytotherapy and Hygiene Research Group, University of Pernambuco, Petrolina, PE, Brazil
| | - Vitor E Valenti
- Center for the Study of the Autonomic Nervous System (CESNA), UNESP, Marilia, SP, Brazil
| | - David M Garner
- Center for the Study of the Autonomic Nervous System (CESNA), UNESP, Marilia, SP, Brazil; Cardiorespiratory Research Group, Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford OX3 0BP, United Kingdom
| | - Taisy C Ferro Cavalcante
- Development, Nutrition, Phytotherapy and Hygiene Research Group, University of Pernambuco, Petrolina, PE, Brazil.
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Abstract
INTRODUCTION AND OBJECTIVES Studies assessing the effects of caffeine (CAF) on the cardiovascular system have demonstrated that CAF can delay cardiac recovery following exercise. This study intended to assess the impact of CAF intake before physical exercise on heart rate variability (HRV) and cardiovascular parameters. METHODS This is a prospective, crossover, controlled clinical trial conducted at the University of Pernambuco, Petrolina, PE, Brazil. The experimental protocol was split into three stages with a minimum of 48 hours between them. Exercises intensity was standardized based on the one repetition maximum test (1RM), obtaining the load of each volunteer for the intensity of 75% of 1RM. In the second and third phases, the control protocols were applied and 300 mg caffeine was given 45 minutes before training. HRV indices were determined at the subsequent times: 0 to 5 minutes of rest (before) and during 30 minutes of recovery (Rec) (after exercise), divided into six intervals, each of 5 minutes. RESULTS The final sample involved 30 volunteers. CAF delayed HRV recovery after resistance exercise. In general, CAF impaired recovery of HRV after resistance exercise. Significant changes were observed in the RMSSD, SDNN, TINN, SD1, low frequency and high frequency indices between the control and CAF group. CONCLUSION CAF protocol delayed parasympathetic regulation of heart rhythm following exercise, slowing recovery of HR, blood pressure and HRV indices after exercise.
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Sivalokanathan S, Małek ŁA, Malhotra A. The Cardiac Effects of Performance-Enhancing Medications: Caffeine vs. Anabolic Androgenic Steroids. Diagnostics (Basel) 2021; 11:diagnostics11020324. [PMID: 33671206 PMCID: PMC7922604 DOI: 10.3390/diagnostics11020324] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 02/10/2021] [Accepted: 02/15/2021] [Indexed: 12/19/2022] Open
Abstract
Several performance-enhancing or ergogenic drugs have been linked to both significant adverse cardiovascular effects and increased cardiovascular risk. Even with increased scrutiny on the governance of performance-enhancing drugs (PEDs) in professional sport and heightened awareness of the associated cardiovascular risk, there are some who are prepared to risk their use to gain competitive advantage. Caffeine is the most commonly consumed drug in the world and its ergogenic properties have been reported for decades. Thus, the removal of caffeine from the World Anti-Doping Agency (WADA) list of banned substances, in 2004, has naturally led to an exponential rise in its use amongst athletes. The response to caffeine is complex and influenced by both genetic and environmental factors. Whilst the evidence may be equivocal, the ability of an athlete to train longer or at a greater power output cannot be overlooked. Furthermore, its impact on the myocardium remains unanswered. In contrast, anabolic androgenic steroids are recognised PEDs that improve athletic performance, increase muscle growth and suppress fatigue. Their use, however, comes at a cost, afflicting the individual with several side effects, including those that are detrimental to the cardiovascular system. This review addresses the effects of the two commonest PEDs, one legal, the other prohibited, and their respective effects on the heart, as well as the challenge in defining its long-term implications.
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Affiliation(s)
- Sanjay Sivalokanathan
- Cardiovascular Clinical Academic Group, St. George’s University of London and St. George’s University Hospitals NHS Foundation Trust, London SW17 0RE, UK;
| | - Łukasz A. Małek
- Department of Epidemiology, Cardiovascular Disease Prevention and Health Promotion, National Institute of Cardiology, 04-628 Warsaw, Poland;
| | - Aneil Malhotra
- Cardiovascular Clinical Academic Group, St. George’s University of London and St. George’s University Hospitals NHS Foundation Trust, London SW17 0RE, UK;
- Division of Cardiovascular Sciences, University of Manchester and Manchester University NHS Foundation Trust, Manchester Institute of Health and Performance, Manchester M11 3BS, UK
- Correspondence:
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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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Pickering C, Grgic J. A time and a place: A framework for caffeine periodization throughout the sporting year. Nutrition 2020; 82:111046. [PMID: 33277148 DOI: 10.1016/j.nut.2020.111046] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 09/10/2020] [Accepted: 10/05/2020] [Indexed: 01/02/2023]
Abstract
Caffeine is a well-established ergogenic aid, with its performance-enhancing effects demonstrated across a variety of sports and exercise types. As a result of these ergogenic properties, caffeine is widely used by athletes at all levels around both competition and training. Caffeine exerts its performance benefits through a variety of mechanisms, each of which may be of increased importance at a given stage of training or competition. Additionally, regular caffeine use may diminish the performance-enhancing effects of a subsequent dose of caffeine. Recently, interest in the concept of nutritional periodization has grown. Here we propose a framework for the periodization of caffeine through the sporting year, balancing its training and competition performance-enhancing effects, along with the need to mitigate any negative effects of habituation. Furthermore, the regular use of caffeine within training may support the development of positive beliefs toward caffeine by athletes-potentially serving to enhance future performance through placebo and expectancy mechanisms-as well as allowing for the optimization of individual athlete caffeine strategies. Although future work is required to validate some of the suggestions made, the framework proposed here represents a starting point for athletes to maximize caffeine's performance benefits across the sporting year.
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Affiliation(s)
- Craig Pickering
- Institute of Coaching and Performance, School of Sport and Wellbeing, University of Central Lancashire, Preston, UK.
| | - Jozo Grgic
- Institute for Health and Sport (IHES), Victoria University, Melbourne, Australia
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Red Bull Increases Heart Rate at Near Sea Level and Pulmonary Shunt Fraction at High Altitude in a Porcine Model. Nutrients 2020; 12:nu12061738. [PMID: 32532046 PMCID: PMC7352389 DOI: 10.3390/nu12061738] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 06/08/2020] [Accepted: 06/08/2020] [Indexed: 12/15/2022] Open
Abstract
Red Bull energy drink is popular among athletes, students and drivers for stimulating effects or enhancing physical performance. In previous work, Red Bull has been shown to exert manifold cardiovascular effects at rest and during exercise. Red Bull with caffeine as the main ingredient increases blood pressure in resting individuals, probably due to an increased release of (nor)-epinephrine. Red Bull has been shown to alter heart rate or leaving it unchanged. Little is known about possible effects of caffeinated energy drinks on pulmonary ventilation/perfusion distribution at sea level or at altitude. Here, we hypothesized a possible alteration of pulmonary blood flow in ambient air and in hypoxia after Red Bull consumption. We subjected eight anesthetized piglets in normoxia (FiO2 = 0.21) and in hypoxia (FiO2 = 0.13), respectively, to 10 mL/kg Red Bull ingestion. Another eight animals served as controls receiving an equivalent amount of saline. In addition to cardiovascular data, ventilation/perfusion distribution of the lung was assessed by using the multiple inert gas elimination technique (MIGET). Heart rate increased in normoxic conditions but was not different from controls in acute short-term hypoxia after oral Red Bull ingestion in piglets. For the first time, we demonstrate an increased fraction of pulmonary shunt with unchanged distribution of pulmonary blood flow after Red Bull administration in acute short-term hypoxia. In summary, these findings do not oppose moderate consumption of caffeinated energy drinks even at altitude at rest and during exercise.
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De Salles Painelli V, Brietzke C, Franco-Alvarenga PE, Canestri R, Vinícius Í, Pires FO. Comment on: “Caffeine and Exercise: What Next?”. Sports Med 2020; 50:1211-1218. [DOI: 10.1007/s40279-020-01278-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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15
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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: 116] [Impact Index Per Article: 19.3] [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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19
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Lund J, S Tangen D, Wiig H, Stadheim HK, Helle SA, B Birk J, Ingemann-Hansen T, Rustan AC, Thoresen GH, Wojtaszewski JFP, T Kase E, Jensen J. Glucose metabolism and metabolic flexibility in cultured skeletal muscle cells is related to exercise status in young male subjects. Arch Physiol Biochem 2018; 124:119-130. [PMID: 28862046 DOI: 10.1080/13813455.2017.1369547] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
We hypothesised that skeletal muscles of healthy young people have a large variation in oxidative capacity and fibre-type composition, and aimed therefore to investigate glucose metabolism in biopsies and myotubes isolated from musculus vastus lateralis from healthy males with varying degrees of maximal oxygen uptake. Trained and intermediary trained subjects showed higher carbohydrate oxidation in vivo. Fibre-type distribution in biopsies and myotubes did not differ between groups. There was no correlation between fibre-type I expression in biopsies and myotubes. Myotubes from trained had higher deoxyglucose accumulation and fractional glucose oxidation (glucose oxidation relative to glucose uptake), and were also more sensitive to the suppressive action of acutely added oleic acid to the cells. Despite lack of correlation of fibre types between skeletal muscle biopsies and cultured cells, myotubes from trained subjects retained some of their phenotypes in vitro with respect to enhanced glucose metabolism and metabolic flexibility.
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Affiliation(s)
- Jenny Lund
- a Department of Pharmaceutical Biosciences , School of Pharmacy, University of Oslo , Oslo , Norway
| | - Daniel S Tangen
- b Department of Physical Performance , Norwegian School of Sport Sciences , Oslo , Norway
| | - Håvard Wiig
- b Department of Physical Performance , Norwegian School of Sport Sciences , Oslo , Norway
| | - Hans K Stadheim
- b Department of Physical Performance , Norwegian School of Sport Sciences , Oslo , Norway
| | - Siw A Helle
- a Department of Pharmaceutical Biosciences , School of Pharmacy, University of Oslo , Oslo , Norway
| | - Jesper B Birk
- c Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science , University of Copenhagen , Copenhagen , Denmark
| | | | - Arild C Rustan
- a Department of Pharmaceutical Biosciences , School of Pharmacy, University of Oslo , Oslo , Norway
| | - G Hege Thoresen
- a Department of Pharmaceutical Biosciences , School of Pharmacy, University of Oslo , Oslo , Norway
- e Department of Pharmacology , Institute of Clinical Medicine, University of Oslo , Oslo , Norway
| | - Jørgen F P Wojtaszewski
- c Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science , University of Copenhagen , Copenhagen , Denmark
| | - Eili T Kase
- a Department of Pharmaceutical Biosciences , School of Pharmacy, University of Oslo , Oslo , Norway
| | - Jørgen Jensen
- b Department of Physical Performance , Norwegian School of Sport Sciences , Oslo , Norway
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McLellan TM, Caldwell JA, Lieberman HR. A review of caffeine’s effects on cognitive, physical and occupational performance. Neurosci Biobehav Rev 2016; 71:294-312. [DOI: 10.1016/j.neubiorev.2016.09.001] [Citation(s) in RCA: 253] [Impact Index Per Article: 31.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Revised: 08/26/2016] [Accepted: 09/04/2016] [Indexed: 12/31/2022]
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Smirmaul BPC, de Moraes AC, Angius L, Marcora SM. Effects of caffeine on neuromuscular fatigue and performance during high-intensity cycling exercise in moderate hypoxia. Eur J Appl Physiol 2016; 117:27-38. [PMID: 27864638 PMCID: PMC5306327 DOI: 10.1007/s00421-016-3496-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Accepted: 10/24/2016] [Indexed: 11/24/2022]
Abstract
Purpose To investigate the effects of caffeine on performance, neuromuscular fatigue and perception of effort during high-intensity cycling exercise in moderate hypoxia. Methods Seven adult male participants firstly underwent an incremental exercise test on a cycle ergometer in conditions of acute normobaric hypoxia (fraction inspired oxygen = 0.15) to establish peak power output (PPO). In the following two visits, they performed a time to exhaustion test (78 ± 3% PPO) in the same hypoxic conditions after caffeine ingestion (4 mg kg−1) and one after placebo ingestion in a double-blind, randomized, counterbalanced cross-over design. Results Caffeine significantly improved time to exhaustion by 12%. A significant decrease in subjective fatigue was found after caffeine consumption. Perception of effort and surface electromyographic signal amplitude of the vastus lateralis were lower and heart rate was higher in the caffeine condition when compared to placebo. However, caffeine did not reduce the peripheral and central fatigue induced by high-intensity cycling exercise in moderate hypoxia. Conclusion The caffeine-induced improvement in time to exhaustion during high-intensity cycling exercise in moderate hypoxia seems to be mediated by a reduction in perception of effort, which occurs despite no reduction in neuromuscular fatigue.
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Affiliation(s)
- Bruno P C Smirmaul
- Department of Physical Education, São Paulo State University (UNESP), Rio Claro, SP, Brazil
| | | | - Luca Angius
- Endurance Research Group, School of Sport and Exercise Sciences, University of Kent at Medway, Chatham Maritime, Kent, ME4 4AG, UK
| | - Samuele M Marcora
- Endurance Research Group, School of Sport and Exercise Sciences, University of Kent at Medway, Chatham Maritime, Kent, ME4 4AG, UK.
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