Hormonal and Metabolite Responses to Glucose and Maltodextrin Ingestion With or Without the Addition of Guar Gum

Abstract The purpose of this study was to examine the effects of ingesting water (P), a glucose solution (GL), a maltodextrin solution (Md), a glucose solution with 8% guar gum (GL + G), and a maltodextrin solution with 8% guar gum (Md + G), on the hormonal and metabolite responses during cycling, and on subsequent time to exhaustion. Five male subjects undertook five 90 min rides on a bicycle ergometer at an exercise intensity corresponding to 65% V̇O 2 max after having ingested lg·kg -1 body weight of the test product in 400 ml of water immediately before the exercise. Blood samples were taken during the trials for analyses of adrenaline, noradrenaline, insulin, glucagon, glucose, lactate and non-esterified fatty acids (NEFA). Respiratory measures were also undertaken during the trials for the determination of oxygen consumption (V̇O 2 ) and respiratory exchange ratio (RER), from which the carbohydrate oxidation rates were calculated. Rates of perceived exertion (RPE) were also assessed. Ten minutes after the 90 min ride, subjects exercised to volitional exhaustion at an exercise intensity of 75% V̇O 2 max. ANOVA revealed that there were significant differences between the treatments for adrenaline (p < 0.01), insulin (p < 0.05), glucose (p < 0.01), lactate (p < 0.01), NEFA (p < 0.01), RER (p < 0.001) and carbohydrate oxidation rate (p < 0.01). Post hoc analyses showed that significantly higher levels of adrenaline were found for P compared to Md (p < 0.05), significantly lower levels of insulin for P compared to Md (p < 0.05), significantly lower levels of glucose and lactate for P compared to all carbohydrate treatments (p < 0.05), significantly higher levels of NEFA for P compared to the carbohydrate treatments (p < 0.05), and significantly lower RER and carbohydrate oxidation rates for ? compared to the carbohydrate trials (p < 0.05). Furthermore, tests highlighted that significantly longer times to exhaustion were achieved by the carbohydrate treatments compared to placebo (p < 0.05). These results support the use of carbohydrate supplementation prior to prolonged exercise, although the type of carbohydrate is not important.