The aim of this study was to ascertain whether a high carbohydrate diet in the days before movement patterns simulating a squash match would increase carbohydrate oxidation during the match, and alter physical performance. Nine New Zealand level squash players were recruited to complete a simulated squash match on two occasions: 1) following a 48-hr high carbohydrate (11.1g·kg-1); and 2) following a calorie-matched low carbohydrate (2.1 g·kg-1) diet. The interventions were assigned in a randomized, single-blind, cross-over design. The match simulation was designed to mimic a five-game match lasting approximately 1 hr. Performance was measured as time to complete each game. Expired respiratory gases and heart rate were continuously collected throughout the trial using a portable gas analysis system. Capillary blood glucose and lactate samples were obtained during a 90 s rest period between each game. Rating of perceived exertion was also recorded after each set. Respiratory exchange ratio was significantly higher during exercise following the high CHO diet (0.80 vs. 0.76) p < .001) and this was associated with significantly faster time to complete the games (2340 ± 189 s vs. 2416 ± 128 s, p = .036). Blood glucose and lactate concentrations were also significantly higher in the high carbohydrate condition (p = .038 and p = .021 respectively). These results suggest that ingestion of a diet high in carbohydrate (>10 g/kg body weight) preceding simulated competitive squash produces increased rates of carbohydrate oxidation and maintains higher blood glucose concentrations. These metabolic effects were associated with improved physical performance.
