INFLUENCE OF ORAL CREATINE SUPPLEMENTATION OF MUSCLE TORQUE DURING REPEATED BOUTS OF MAXIMAL VOLUNTARY EXERCISE IN MAN

1. The present experiment was undertaken to investigate the influence of oral creatine supplementation, shown previously to increase the tot al creatine content of human skeletal muscle (Harris RC, Soderlund K, Hultman E. Clin Sci 1992; 83: 367-74), on skeletal muscle isokinetic t orque and the accumulation of plasma ammonia and blood lactate during five bouts of maximal exercise. 2. Twelve subjects undertook five bout s of 30 maximal voluntary isokinetic contractions, interspersed with 1 min recovery periods, before and after 5 days of placebo (4 x 6 g of glucose/day, n = 6) or creatine (4 x 5 g of creatine plus 1 g of gluco se/day, n = 6) oral supplementation. Muscle torque production and plas ma ammonia and blood lactate accumulation were measured during and aft er exercise on each treatment. 3. No difference was seen when comparin g muscle peak torque production during exercise before and after place bo ingestion. After creatine ingestion, muscle peak torque production was greater in all subjects during the final 10 contractions of exerci se bout 1 (P<0.05), throughout the whole of exercise bouts 2 (P<0.01), 3 (P<0.05) and 4 (P = 0.057) and during contractions 11-20 of the fin al exercise bout (P<0.05), when compared with the corresponding measur ements made before creatine ingestion. Plasma ammonia accumulation was lower during and after exercise after creatine ingestion. No differen ces were found when comparing blood lactate levels. 4. There is eviden ce to suggest that the decrease in the degree of muscle torque loss af ter dietary creatine supplementation may be a consequence of a creatin e-induced acceleration of skeletal muscle phosphocreatine resynthesis. It is postulated that an increased availability of phosphocreatine wo uld maintain better the required rate of ATP demand during contraction . This is supported by the observed lower accumulation of plasma ammon ia during exercise after creatine ingestion.