Effect of creatine plus caffeine supplements on time to exhaustion during an incremental maximum exercise

This study investigated the effects of acute caffeine ingestion following short-term creatine supplementation on an incremental cycling to exhaustion task. Twelve active males performed the task under three conditions: baseline condition (BASE, no ergogenic aid), creatine plus caffeine condition (CRE + CAF), and creatine with placebo condition (CRE + PLA). Following the establishment of BASE condition, participants were administered CRE + CAF (0.3 g·kg ^-1·day ^-1 of creatine for 5 days followed by 6 mg·kg ^-1 of caffeine 1 h prior to testing) and CRE + PLA (0.3 g·kg ^-1·day ^-1 of creatine for 5 days followed by 6 mg·kg ^-1 of placebo 1 h prior to testing) in a double-blind, randomized crossover and counterbalancing protocol. No significant differences were observed in relative maximal oxygen consumption (V̇O _2max) (51.7±5.5, 52.8±4.9 and 51.3±5.6 ml·kg ^-1·min ^-1 for BASE, CRE + CAF and CRE + PLA, respectively; P>0.05) and absolute V̇O _2max (3.6±0.4, 3.7±0.4 and 3.5±0.5 l·min ^-1 for BASE, CRE + CAF and CRE + PLA, respectively; P>0.05). Blood samples indicated significantly higher blood lactate and glucose concentrations in the CRE + CAF among those in the BASE or CRE + PLA condition during the test (P<0.05). The time to exhaustion on a cycling ergometer was significantly longer for CRE + CAF (1087.2±123.9 s) compared with BASE (1009.2±86.0 s) or CRE + PLA (1040.3±96.1 s). This study indicated that a single dose of caffeine following short-term creatine supplementation did not hinder the creatine-caffeine interaction. In fact, it lengthened the time to exhaustion during an incremental maximum exercise test. However, this regime might lead to the accumulation of lactate in the blood.