Nutritional supplements containing carbohydrate and protein and/or creatine are widely consumed by athletes in training. There have been few chronic nutritional intervention studies evaluating the physiological effects of such supplements for athletes in training using controlled laboratory measures. Past studies include those that have involved untrained subjects completing a resistance-training programme (e.g. Antonio et al, 2000), so cannot be generalised to highly trained athletes. We hypothesised that ingestion of carbohydrate, protein and creatine over 10 weeks of primarily endurance type training would increase the rate of adaptation to training compared with carbohydrate alone. Twelve swimmers and tri-athletes completed the study out of fifteen volunteers. The study was a repeated measures double blind design with two groups CHO-PRO-Cr and CHO (matched based on aerobic capacity). The CHO-PRO-Cr group consumed a carbohydrate, protein and creatine supplement while the CHO group consumed a carbohydrate supplement following training (up to 11 sessions per week) for 10 weeks. Body composition (air displacement plethsmography), muscle function (Biodex dynamometer) and aerobic capacity (VO2peak; on-line metabolic cart) were assessed at baseline, 5 weeks and 10 weeks supplementation. A 7-day food diary was completed using weighed food portions at baseline. Muscle function was assessed during bilateral knee and shoulder isometric and isokinetic tests at 90 degrees/s and 180 degrees/s. VO2peak was assessed during an incremental cycle test to exhaustion. Data was analyzed using repeated measures ANOVA at p0.05) and no interaction effect present. There were no significant differences in the rate of improvement over 10 weeks in body composition, muscle function and VO2peak when consuming CHO-PRO-Cr supplement regularly after training compared with a CHO supplement, suggesting that this supplement did not increase the rate of adaptation to training compared with CHO supplementation.