CREATINE INGESTION FAVORABLY AFFECTS PERFORMANCE AND MUSCLE METABOLISM DURING MAXIMAL EXERCISE IN HUMANS

Nine male subjects performed two bouts of 30-s maximal isokinetic cycl ing before and after ingestion of 20 g creatine (Cr) monohydrate/day f or 5 days. Cr ingestion produced a 23.1 +/- 4.7 mmol/kg dry matter inc rease in the muscle total creatine (TCr) concentration. Total work pro duction during bouts 1 and 2 increased by similar to 4%, and the cumul ative increases in both peak and total work production over the two ex ercise bouts were positively correlated with the increase in muscle TC r. Cumulative loss of ATP was 30.7 +/- 12.2% less after Cr ingestion, despite the increase in work production. Resting phosphocreatine (PCr) increased in type I and II fibers. Changes in PCr before exercise bou ts I and 2 in type II fibers were positively correlated with changes i n PCr degradation during exercise in this fiber type and changes in to tal work production. The results suggest that improvements in performa nce were mediated via improved ATP resynthesis as a consequence of inc reased PCr availability in type II fibers.