THE EFFECTS OF PREEXERCISE STARCH INGESTION ON ENDURANCE PERFORMANCE

This study compared the physiological responses and performance follow ing the ingestion of a waxy starch (WS), resistant starch (RS), glucos e (GL) and an artifiially-sweetened placebo (Pi.) ingesed prior to exe rcise. Ten college-age, male competitive cyclists completed four exper imental protocols consisting of a 30 min isokinetic, self-paced perfor mance ride preceded by 90 min of constant load cycling at 66 % VO(2)ma x. Thirty min prior to exercise, they ingested 1 g . kg(-1) body weigh t of GL, WS, RS, or PL. At rest, GL elicited greater (p<0.05) serum gl ucose and insulin responses than all other trials. During exercise, ho wever, serum glucose, insulin, blood C-peptide and glucagon responses were similar among trials. The mean total carbohydrate oxidation rates (CHOox) were higher (p<0.05) during the GL, WS, and RS trials (2.59+/ -0.13, 2.49+/-0.10, and 2.71+/-0.15 g min(-1), respectively) compared to PL (2.35+/-0.12 g min(-1)). Subjects were able to complete more wor k (p<0.05) during the performance ride when they ingested GL (434+/-25 .2 kJ) or WS (428+/-22.5 kJ) compared to PL (403+/-35.1 kJ). They also tended to produce more work with RS ingestion (418+/-31.4 kJ), althou gh this did not reach statistical significance (p<0.09). these results indicate that preexercise-CHO ingestion in the form of starch or gluc ose maintained higher rates of total carbohydrate oxidation during exe rcise and provided an ergogenic benefit during self-paced cycling.