THE EFFECTS OF PRE-EXERCISE TREHALOSE, GALACTOSE AND GLUCOSE INGESTION ON METABOLISM AND CYCLING PERFORMANCE

Abstract

Glucose feedings in the hour prior to exercise can cause rebound hypoglycemia 15–30 min after the onset of exercise. The extent to which hypoglycemia affects performance is largely unknown. Pre-exercise carbohydrates that produce minimal glycemic and insulinemic responses have been suggested to be the preferred type of carbohydrate for consumption prior to exercise performance. PURPOSE: The purpose of the present study was to examine the effects of pre-exercise ingestion of glucose (GLU), galactose (GAL) and trehalose (TRE) on metabolic responses at rest and during cycling exercise and on time trial performance. METHODS: Eight trained male cyclists (VO2max: 61.5 ± 1.6 mlkg−1min−1) completed 3 exercise trails in random order. Forty-five min before the start of exercise subjects consumed 500 ml of a beverage containing 75 g of either GLU, GAL or TRE. The exercise trials consisted of 20 min of submaximal steady state exercise (SS) at 65% of maximal power output (75 ± 1% VO2max) immediately followed by a 702 ± 25 kJ time trial (TT). RESULTS: Plasma glucose concentration 15 min postprandial was significantly higher in GLU compared with GAL and TRE (P < 0.05). This was accompanied by a more than twofold higher rise in plasma insulin in GLU compared with GAL and TRE (118% and 145%, respectively). During SS exercise 4 subjects in GLU and 1 subject in TRE developed rebound hypoglycemia (< 3.5 mmolL−1). No differences were observed in TT performance between the three trials. CONCLUSION: Pre-exercise ingestion of TRE and GAL resulted in lower plasma glucose and insulin responses prior to exercise and reduced the prevalence of rebound hypoglycemia. Despite attenuated insulin and glucose responses at rest and during exercise following pre-exercise GAL and TRE feedings, there was no difference in TT performance compared with pre-exercise ingestion of GLU.