THE INFLUENCE OF DIETARY CARBOHYDRATE ON PERFORMANCE OF SUPRAMAXIMAL INTERMITTENT EXERCISE

The present investigation examined the influence of dietary carbohydra te (CHO) on the performance of supramaximal intermittent exercise. A g roup of 14 moderately trained male students [mean age 21.0 (SD 1.6) ye ars] completed a maximal oxygen consumption test and two identical 'ma ximal interval tests' (MIT1 and MIT2) over a 10-day experimental perio d. Each MIT involved five 60-s all-out periods of cycling (against 0.7 36 N . kg-1 body mass), with each period separated by 5 min of passive recovery. All subjects consumed a moderate CHO diet for 3 days preced ing MIT1 (55.3% of energy intake as CHO) and were then randomly assign ed to either a high CHO (83%), moderate CHO (58%) or low CHO (12%) die t for the 3 days separating MIT1 and MIT2. All food and drink consumed during the experimental period was weighed and recorded for later die tary analysis. Measurements of work done, exercise oxygen consumption (VO2), venous blood pH, plasma lactate and plasma glucose concentratio ns were compared between interval tests. Independent Student's t-tests revealed that the 5.6% increase in total work done recorded by the hi gh CHO group and the 2.3% increase by the moderate CHO group between M IT1 and MIT2, were significantly different to the 5.4% decrease in per formance recorded for the low CHO group (P<0.001 and P<0.01, respectiv ely). No significant differences in performance changes was found betw een the high and moderate CHO groups; 10 subjects in each of these gro ups would have been necessary to attain significance at the 0.05 level using the same procedures. No changes in VO2, venous blood pH, plasma lactate or glucose concentrations were found among the groups. These data showed that when compared to a low CHO diet, a moderate/high inta ke of dietary CHO could at least maintain the performance of supramaxi mal intermittent exercise. The results emphasise the importance of die tary CHO for athletes whose activities involve repeated periods of ver y high intensity exercise.