Abstract
The purpose of this study is to investigate the effects of ingesting either a high glycaemic index (HGI) or low glycaemic index (LGI) carbohydrate meal (preceding a 12 h overnight fast and where the meal was ingested 45-min prior to activity) on intermittent sprint and endurance exercise performance. Ten male varsity athletes from intermittent sports (age 23.6 ± 1.7 years, VO2max 51.9 ± 4.7 mL·kg−1·min−1) underwent a peak velocity (Vpeak) test and familiarisation session, followed by two experimental sessions in random order. Experimental sessions involved the ingestion of either an HGI or LGI meal, followed by the completion of the modified Loughborough Intermittent Shuttle Test (mLIST). There was no significant difference between HGI or LGI meals on sprint times (p = 0.62) and distance to exhaustion (p = 0.54) in the mLIST. Exercise heart rate, blood lactate and ratings of perceived exertion were also similar between the two meal trials throughout the mLIST (all p > 0.05). Subjective ratings of hunger, fullness, satiety and satisfaction were also not significantly different between the two meals. In conclusion, consuming either an HGI or LGI meal after a prolonged 12 h fast and ingesting the meal 45 min prior to exercise did not differ in either physiological, subjective and intermittent sprint and endurance performance outcomes.
Highlights
The glycaemic index (GI) was established to enable the comparison of human physiological responses towards varying types of food and to develop food items which, when ingested, would lead to a relatively slower or more gradual increase in blood glucose concentration levels, especially for people with diabetes or glucose intolerance [1]
A significant time effect on sprint times was observed in both meal conditions (p = 0.05), but no significant difference was found between the two meal trials at any time point throughout the modified Loughborough Intermittent Shuttle Test (mLIST) (p > 0.05, ηp 2 = 0.33)
For the distance to exhaustion performance, paired sample t-test showed no significant difference in the distance covered between the two meal trials (p = 0.54), the distance to exhaustion in the high glycaemic index (HGI)
Summary
The glycaemic index (GI) was established to enable the comparison of human physiological responses towards varying types of food and to develop food items which, when ingested, would lead to a relatively slower or more gradual increase in blood glucose concentration levels, especially for people with diabetes or glucose intolerance [1]. Calculation of the GI value of the food is based on an individual’s postprandial glycaemia response after the ingestion of a CHO-containing food in comparison to the response observed from the consumption of an equivalent portion of reference food (i.e., 50 g of glucose) [1] In this regard, high glycaemic index (HGI) foods (GI value of >70), are rapidly digested and absorbed into the body, resulting in rapid increases in blood glucose levels per unit of CHO in comparison to low glycaemic index (LGI) foods (GI value of
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