Effect of glucose polymer diet supplement on responses to prolonged successive swimming, cycling and running

Summary

Fifteen male endurance athletes were studied to determine the effect of a glucose polymer (GP) diet supplement on physiological and perceptual responses to successive swimming, cycling and running exercise. Thirty min of swimming, cycling and running at 70% $\dot V_{{\text{O}}_{{\text{2}} {\text{max}}} }$, followed by a run to exhaustion at 90% $\dot V_{{\text{O}}_{{\text{2}} {\text{max}}} }$ was performed after one week of training under two dietary conditions: 1) GP (230 g of GP consumed daily) and 2) placebo (P, saccharin-sweetened supplement consumed daily). During GP, daily carbohydrate (CHO) intake was higher (p<0.05) by 173 g or 14% of energy intake than during P, but total energy intake was not significantly different. During 90 min of exercise, CHO utilization and blood glucose were significantly higher under GP than P by an average of 20.2% and 14.5%, respectively, but heart rate, ventilation, oxygen uptake, ratings of perceived exertion, and plasma lactate were not different. Run time to exhaustion at 90% $\dot V_{{\text{O}}_{{\text{2}} {\text{max}}} }$ was significantly longer by 1.2 min (23%) under GP. The results suggest that a GP diet supplement may be of value during endurance exercise by increasing the availability of CHO.