title: Ingestion of a moderately high caffeine dose before exercise increases postexercise energy expenditure.
abstract: 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.
authors.affiliation: Exercise Physiology Laboratory, University of Castilla-La Mancha, Toledo, Spain.
authors.forename: Valentín E
authors.initials: VE
authors.lastname: Fernández-Elías
authors.forename: Juan
authors.initials: J
authors.lastname: Del Coso
authors.forename: Nassim
authors.initials: N
authors.lastname: Hamouti
authors.forename: Juan F
authors.initials: JF
authors.lastname: Ortega
authors.forename: Gloria
authors.initials: G
authors.lastname: Muñoz
authors.forename: Jesus
authors.initials: J
authors.lastname: Muñoz-Guerra
authors.forename: Ricardo
authors.initials: R
authors.lastname: Mora-Rodríguez
mesh_terms: D000328:Adult; D001642:Bicycling; D002110:Caffeine / Q000008:administration & dosage* / Q000009:adverse effects; D019587:Dietary Supplements / Q000009:adverse effects; D004311:Double-Blind Method; D004734:Energy Metabolism; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D056152:Respiratory Rate; D012420:Running; D013030:Spain; D064133:Sports Nutritional Physiological Phenomena; D011795:Surveys and Questionnaires; D013990:Tidal Volume; D013997:Time Factors; D015854:Up-Regulation; D055815:Young Adult
chemical_list: D002110:Caffeine