EFFECT OF ORAL CREATINE INGESTION ON PARAMETERS OF THE WORK RATE-TIMERELATIONSHIP AND TIME TO EXHAUSTION IN HIGH-INTENSITY CYCLING

The relationship between work rate ((W) over dot) and time to exhausti on (t) during intense exercise is commonly described by either a hyper bolic function (NLin), t = W'/((W) over dot-(W) over dot(cp)), or by i ts linear equivalent (LinW) W-lim = W' + (W) over dot(cp)(t). The para meter (W) over dot(cp) (critical power) has been described as an inher ent characteristic of the aerobic energy system, while W' has been sho wn to be a ralid estimate of anaerobic work capacity. Recent studies h ave demonstrated that oral supplementation of creatine monohydrate (Cr H2O) increases total muscle creatine stores, and have linked these inc reases to improved performances in intense intermittent exercise. This study was conducted to determine the effect of CrH2O supplementation on estimates of W' and (W) over dot(cp) derived from the NLin and LinW equations, and to determine the effect of CrH2O on t in exhaustive co nstant power exercise of different intensities. Fifteen active but unt rained university students completed three phases of testing on a cycl e ergometer: (1) familiarization, three learning trials, (2) baseline determination of W' and (W) over dot(cp), four bouts performed at a (W ) over dot selected to elicit fatigue in 90-600 s, and (3) experimenta l determination of W' and (W) over dot(cp), four bouts performed at th e same (W) over dot as baseline, but performed after 5 days of ingesti ng either a placebo (4 x 6 g of glucose/day) or CrH2O (4 x 5 g of CrH2 O and 1 g glucose/day). Testing was administered in a double-blind man ner. Analyses of covariance revealed a significant effect for CrH2O on both estimates of W' (NLin, P = 0.04; LinW, P < 0.01), but not on est imates of (W) over dot(cp) (NLin, P = 0.37; LinW; P = 0.30). Within gr oups, t was significantly different for only CrH2O at the two highest (W) over dots (P = 0.04). It is concluded that oral ingestion of CrH2O increases estimates of W' due to an improved t at the shorter, more i ntense exercise bouts.