Effects of pre-exercise ingestion of trehalose, galactose and glucose on subsequent metabolism and cycling performance

Abstract

The glycaemic and insulinaemic responses to different carbohydrates vary and these have been suggested to affect performance. The purpose of the present study was to determine the effects of pre-exercise ingestion of glucose (GLU), galactose (GAL) and trehalose (TRE) on metabolic responses at rest and during exercise and on subsequent time-trial (TT) performance. Eight well-trained male cyclists completed three exercise trials separated by at least 3 days. At 45 min before the start of exercise subjects consumed 500 ml of a beverage containing 75 g of either glucose, galactose or trehalose. The exercise trials consisted of 20 min of submaximal steady-state exercise (SS) at 65% of maximal power output immediately followed by a [mean (SEM)] 702 (25) kJ TT. Plasma glucose concentration 15 min postprandial was significantly higher in GLU compared to GAL and TRE (P<0.05). This was accompanied by a more than twofold greater rise in plasma insulin concentration in GLU compared to GAL and TRE (118% and 145%, respectively). During SS exercise four subjects in GLU and one subject in TRE developed a rebound hypoglycaemia (plasma glucose concentration less than 3.5 mmolAEl -1 ). No differences were observed in TT performance between the three trials. Pre-exercise ingestion of trehalose and galactose resulted in lower plasma glucose and insulin responses prior to exercise and reduced the prevalence of rebound hypoglycaemia. Despite the attenuated insulin and glucose responses at rest and during exercise following pre-exercise ingestion of galactose and trehalose, there was no difference in TT performance compared with pre-exercise ingestion of glucose.

Effect of Galactose Ingestion Before and During Exercise on Substrate Oxidation, Postexercise Satiety, and Subsequent Energy Intake in Females

“…These findings are in agreement with previous studies reporting no differences in whole body substrate utilization during exercise at 65% VO 2peak , after pre-exercise consumption of glucose, galactose or trehalose [46] or galactose, glucose and fructose combinations [47]. It is therefore likely that the continuous intake of the drinks throughout the exercise period, or the moderate intensity of the exercise protocol, resulted in a reduction in glucose requirements as the main fuel substrate.…”

The Effect of the Timing of Meal Intake on Energy Metabolism during Moderate Exercise

“…Although, Dumortier et al (28) reported that when a meal of 550 kcal · · · · · · (57% CHO, 26% protein, and 17% fat) was consumed 1 h or 3 h before exercise by diabetes patients, fat oxidation was higher after 3 h compared with 1 h during exercise. Moreover, the amount of carbohydrate intake in the present study was 2.4 g/kg body mass, which was higher than in previous studies (approximately 1.0-2.2 g/kg body mass) (4,5,7,8). The meal form was also in contrast to many previous studies in which beverages or simple foods were used.…”

“…Fats are supplied by meals, and also by adipose tissues, but CHO must be acquired from meals before exercise because little is stored as glycogen in the liver or muscle tissue. Previous studies have been conducted on the ergogenic effects of CHO feeding before exercise (1)(2)(3)(4)(5)(6)(7)(8)(9)(10). It was reported that CHO solution (such as glucose and maltodextrin) feeding before exercise can improve exercise performance through enhanced endurance exercise capacity (2,4,5,10).…”

“…On the other hand, Coyle et al (13) have shown that carbohydrate utilization during exercise is higher under the condition of meal intake at 4 h before exercise compared with the fasting condition. Therefore, regardless of the timing of carbohydrate intake, it is likely that carbohydrate intake before exercise promotes its utilization as a major energy (2,4,5,(7)(8)(9)(10)(11), although other studies showed no effect (14,15). Tokmakidis and Karamanolis (10) reported that the ingestion of a glucose solution (1 g·kg body mass 21 ) at 15 min before exercise improves endurance running capacity.…”

The effect of galactose supplementation on endurance cycling performance

“…One employed a 20-min warm up at 65% maximal oxygen uptake (VO 2max ) followed by a self-paced time trial (TT) of B40 min (Jentjens and Jeukendrup, 2003). No effect of galactose ingestion on performance was apparent.…”