Effect Of Acute Caffeine Intake Research Articles

Effect of caffeine intake on EPOC after resistance training

The purpose of the study was to examine the effect of caffeine (CAF) intake on excess post‐exercise oxygen consumption (EPOC) in response to resistance training. Five strength‐trained men (mean ± SE age and mass = 21.1 ± 2.2 yr and 87.8 ± 15.4 kg) who were regular CAF consumers took part in the study. A randomized, double‐blind, crossover design was used. One week apart, CAF (6 mg/kg body weight) or placebo housed in identical capsules was ingested with water 1 h pre‐exercise. Pre‐exercise, subjects sat in a chair for 30 min to assess oxygen uptake (VO2). Subjects completed four sets of bench press, leg press, lat row, and shoulder press to fatigue at 75 – 80 % one‐repetition maximum. After exercise, EPOC was assessed for 75 min. VO2 was increased (p < 0.05) from pre‐exercise (0.30 ± 0.02 L/min) to 5 min after exercise (0.53 ± 0.04 L/min), and EPOC remained elevated (p < 0.05) after 75 min of rest (0.36 ± 0.03 L/min). CAF increased calorie expenditure before and after exercise, but it failed to reach significance (p > 0.05). There was no effect (p > 0.05) of CAF on VO2, VCO2, or RER. Compared to placebo, data suggest no effect of a 6 mg/kg dose of CAF on resting VO2 or EPOC. A larger sample size may be needed to show a significant effect of acute CAF intake on EPOC after rigorous resistance training.This project was funded by a University Professional Development/Research, Scholarship, and Creative Activity Grant.

Effect of chronic caffeine intake on choice reaction time, mood, and visual vigilance

The stimulatory effects of acute caffeine intake on choice reaction time, mood state, and visual vigilance are well established. Little research exists, however, on the effects of chronic caffeine ingestion on psychomotor tasks. Therefore, the purpose of this study was to evaluate the effects of 5 days of controlled caffeine intake on cognitive and psychomotor performance. Three groups of 20 healthy males (age = 22 ± 3 years, mass = 75.4 ± 7.9 kg, body fat percentage = 11.2 ± 5.1%) twice completed a battery of cognitive and psychomotor tasks: after 6 days of 3 mg·kg − 1 day − 1 caffeine equilibration (Day 6), and after 5 days of experimental (0 [G0], 3 [G3], or 6 [G6] mg·kg − 1 day − 1 ) caffeine intake (Day 11). Groups were randomized and stratified for age, mass, and body composition; all procedures were double-blind. Cognitive analyses involved a visual four-choice reaction time test, a mood state questionnaire, and a visual vigilance task. Experimental chronic caffeine intake did not significantly alter the number of correct responses or the mean latency of response for either the four-choice reaction time or the visual vigilance tasks. The Vigor–Activity subset of the mood state questionnaire was significantly greater in G3 than G0 or G6 on Day 11. All other mood constructs were unaffected by caffeine intake. In conclusion, few cognitive and psychomotor differences existed after 5 days of controlled caffeine ingestion between subjects consuming 0, 3, or 6 mg·kg − 1 day − 1 of caffeine, suggesting that chronic caffeine intake (1) has few perceptible effects on cognitive and psychomotor well-being and (2) may lead to a tolerance to some aspects of caffeine's acute effects.