Effect Of Caffeine Ingestion After Creatine Supplementation On High-intensity Cycling Sprint Performance

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Previous studies showed that ingestion of caffeine together with creatine may inhibit the effects of creatine on anaerobic exercise. Although some studies indicated that ingested caffeine after short-term creatine supplementation could increase maximal accumulated oxygen deficit, there was no evidence to prove whether this supplementary method could facilitate stop-and-go exercise performance. PURPOSE: This study was to investigate the effects of caffeine ingestion after creatine supplementation on intermittent high-intensity cycling sprints performance. METHODS: Twelve physically active men were administered in a double-blind, randomized, counterbalanced design to perform intermittent high-intensity sprints (6×10-s; repeated at 60-s intervals, HIS) on a cycling ergometer with or without caffeine ingestion. After short-term creatine monohydrate supplementation (0.3 g · kg-1 · day-1, 5 days), subjects ingested 6 mg · kg-1 caffeine or placebo (maltodextrin) 1 hour before HIS trials. Heart rate was monitored continuously throughout the tests, with rating of perceived exertion (RPE) recorded after each sprint. Earlobe blood samples were also drawn immediately after each sprint to evaluate lactate and glucose concentrations. RESULTS: Compared with placebo, caffeine did not resulted in higher maximal power output (842.3±102.2 vs. 813.5±95.3 watts, p>0.05). However, the relative peak power output in caffeine treatment was significantly higher than in placebo during the first sprint (11.7±0.7 vs. 11.3±0.7 watts · kg-1, p<0.05) and second sprint (11.5±0.7 vs. 10.8±0.7 watts · kg-1, p<0.05). Heart rates were significantly increased with caffeine treatment from the third sprint to the final sprint, and the blood lactate and glucose concentrations were also significantly elevated through the HIS trial. Furthermore, there were no significant effects of caffeine ingestion on the RPE scores. CONCLUSIONS: The present study showed that caffeine ingestion after short-term creatine supplementation could improve intermittent high-intensity sprints performance, but might also induce higher metabolic stress.