Abstract
INTRODUCTION: To ensure performance and health, the type of food and the time of pre-exercise ingestion should be considered by practitioners of morning physical activity. Objective: This study assessed the metabolic response after pre-exercise meals with different glycemic indexes (GI) and in the fasting state adopting different types of hydration.METHODS: Twelve men performed four experimental tests; two with pre-exercise meals of high GI (HGI) and low GI (LGI), and two were performed in the fasting state with hydration: water (H2O) and carbohydrate drink (CHO). Each test consisted of a pre-exercise rest period of 30 minutes followed by 60 minutes of cycle ergometer with continuous load equivalent to 60% of the extrapolated maximal oxygen consumption (VO2MaxExt). During the exercise, participants were hydrated every 15 minutes with 3mL per kg body weight. During each experimental test, venous blood samples were obtained for fasting and at 15-minute intervals during rest, and every 20 minutes during exercise. The gas analysis was carried out in periods of 5 minutes every 20 minutes of exercise.RESULTS: There was no difference in substrate oxidation. After 20 minutes of exercise, pre-exercise food intake procedures showed similar behavior, having only reduced blood glucose levels compared to fasting procedures (p<0.01). There was maintenance of blood glucose at stable and higher levels during exercise in relation to the other tests in the fast procedure with CHO.CONCLUSION: The data suggest that despite the similar metabolic behavior between LGI and HGI meals, the adoption of a LGI meal before the morning exercise seems to be a more suitable feeding practice due to higher tendency of rebound hypoglycemia after HGI meal and when morning exercise is performed on fasting, hydration with CHO seems to minimize the hypoglycemic risk arising from that state.
Highlights
To ensure performance and health, the type of food and the time of pre-exercise ingestion should be considered by practitioners of morning physical activity
After 20 minutes of exercise, pre-exercise food intake procedures showed similar behavior, having only reduced blood glucose levels compared to fasting procedures (p
The data suggest that despite the similar metabolic behavior between low GI (LGI) and high GI (HGI) meals, the adoption of a LGI meal before the morning exercise seems to be a more suitable feeding practice due to higher tendency of rebound hypoglycemia after HGI meal and when morning exercise is performed on fasting, hydration with CHO seems to minimize the hypoglycemic risk arising from that state
Summary
To ensure performance and health, the type of food and the time of pre-exercise ingestion should be considered by practitioners of morning physical activity. Special attention is devoted to the performance of morning physical activity because due to climatic conditions and labor activities, it is a time of great preference by the population, and it is the time of day in which the individual’s muscle and liver glycogen reserves are depleted due to the overnight fasting period[3] In this context, it is known that in practical terms, the time prior to physical activity for food intake is restricted[4], and breakfast can lead to rebound hypoglycemia[5], which occurs due to high glucose uptake by the muscle, caused by the action of high insulin levels, which inhibits lipolysis, added to the muscular action itself[1]. Training performed in total fasting state can accelerate the onset of a hypoglycemia condition during exercise, which is harmful
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