Ingestion of a Moderately High Caffeine Dose Before Exercise Increases Postexercise Energy Expenditure
in International Journal of Sport Nutrition and Exercise MetabolismClick name to view affiliation
Caffeine is an ergogenic aid widely used before and during prolonged exercise. Due to its prolonged biological half-life caffeine effects could remain after exercise. We aimed to investigate the metabolic, respiratory, and cardiovascular postexercise responses to preexercise graded caffeine ingestion. Twelve aerobically trained subjects (mean VO2max = 54 ± 7 ml · min−1 · kg−1) cycled for 60-min at 75% VO2max after ingesting placebo (0 mg of caffeine per kg of body weight) or 0.5, 1.5, 3.0 and 4.5 mg · kg−1 on five occasions. During the 3 hr postexercise, heart rate, blood pressure, glucose, lactate, and fatty acids were analyzed. None of these variables were statistically affected by preexercise caffeine ingestion between 0.5 and 4.5 mg · kg−1. However, ingestion of 4.5 mg · kg−1 of caffeine raised postexercise energy expenditure 15% above placebo (233 ± 58 vs. 202 ± 49 kcal/3 hr; p < .05). Ventilation and tidal volume were elevated after the 4.5 mg·kg−1 caffeine dose above placebo (9.2 ± 2.5 L · min−1 and 0.67 ± 0.29 L · breath−1 vs. 7.8 ± 1.5 L · min−1 and 0.56 ± 0.20 L · breath−1, respectively; p < .05). Ventilation correlated with tidal volume (r = .45; p < .05) and energy expenditure (r = .72; p < .05). In summary, preexercise ingestion of ergogenic caffeine doses do not alter postexercise cardiovascular responses. However, ingestion of 4.5 mg · kg−1 of caffeine raises 3-hr postexercise energy expenditure (i.e., 31 kcal) likely through increased energy cost of ventilation.
Fernández-Elías, Hamouti, Ortega, and Mora-Rodríguez are with the Exercise Physiology Laboratory, University of Castilla-La Mancha, Toledo, Spain. Coso is with the Exercise Physiology Laboratory, Camilo José Cela University, Madrid, Spain. Muñoz and Muñoz-Guerra are with the Spanish Antidoping Agency, Doping Control Laboratory, Madrid, Spain.
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