THE INFLUENCE OF DIETARY CREATINE SUPPLEMENTATION ON PERFORMANCE DURING REPEATED BOUTS OF MAXIMAL ISOKINETIC CYCLING IN MAN

The effect of dietary creatine (Cr) supplementation on performance dur ing 3, 30 s bouts maximal isokinetic cycling and on plasma ammonia and blood lactate accumulation during exercise was investigated. Placebo (P) ingestion had no effect on peak power output PPO), mean power outp ut (MPO) and total work output during each bout of exercise. Cr ingest ion (4 x 5 g.day(-1) for 5 days) significantly increased PPO in exerci se bout 1 p<0.05) and MPO and total work output in exercise bouts 1 p< 0.05, p<0.05, respectively) and 2 (p<0.05, p<0.05, respectively). Cr i ngestion had no effect on any of the measures of performance during ex ercise bout 3. No difference was observed in peak plasma ammonia accum ulation before (146 + 30 mu mol.l(-1)) and after (122 +/- 17 mu mol.l( -1)) P ingestion, however the corresponding concentration was lower fo llowing Cr ingestion (129 +/- 22 mu mol.l(-1)) compared with before Cr ingestion (160 +/- 18 mu mol.l(-1), p<0.05), despite subjects perform ing more work. No difference in peak blood lactate accumulation was ob served before and after P or Cr ingestion. The results demonstrate tha t Cr ingestion can increase whole body exercise performance during the initial two, but not a third, successive bout of maximal exercise las ting 30 s. The lower accumulation of plasma ammonia under these condit ions suggests this response is achieved by an effect on muscle ATP tur nover.