EFFECT OF CREATINE SUPPLEMENTATION ON INTRAMUSCULAR TCR, METABOLISM AND PERFORMANCE DURING INTERMITTENT, SUPRAMAXIMAL EXERCISE IN HUMANS

This study examined the effect of(a) creatine supplementation on exerc ise metabolism and performance and (b) changes in intramuscular total creatine stores following a 5 day supplementation period and a 28 day wash-out period. Six men performed four exercise trials, each consisti ng of four 1 min cycling bouts, punctuated by 1 min of rest followed b y a fifth bout to fatigue, all at a workload estimated to require 115 or 125% VO2,max. After three familiarization trials, one trial was con ducted following a creatine monohydrate supplementation protocol (CREA T); the other after 28 d without creatine supplementation, in which th e last 5 d involved placebo ingestion (CON). Intramuscular TCr was ele vated (P < 0.05) in CREAT compared with the final familiarization tria l (FAM3) and CON. Concentrations of this metabolite in these latter tr ials were not different. In addition, a main effect (P < 0.05) for tre atment was observed for PCr when the data from CREAT were compared wit h CON. In contrast, no differences were observed in the total adenine nucleotide pool (ATP+ADP+AMP), inosine 5'-monophosphate, ammonia, lact ate or glycogen when comparing CREAT with CON. Despite the differences in TCr and PCr concentrations when comparing CREAT with other trials, no difference was observed in exercise duration in the fifth work bou t. These data demonstrate that creatine supplementation results in an increase in TCr but this has no effect on performance during exercise of this nature, where the creatine kinase system is not the principal energy supplier. In addition 28 d without supplementation is a suffici ent time to return intramuscular TCr stores to basal levels.