BLOOD GLUCOSE RESPONSE BEFORE AND DURING EXERCISE: THE EFFECTS OF FASTING AND MEALS WITH HIGH AND LOW GLYCEMIC INDICES
Journal Title: Medicina Sportiva - Year 2013, Vol 17, Issue 2
Abstract
Objective: This study aimed to investigate the effects of 60-minute running in a fasting state compared to ingesting low and high glycemic index (GI) breakfasts one hour prior to exercise on plasma glucose and physiologic parameters in physically active adults. Methods: Fifteen men completed three trials in a randomized counterbalanced order. One hour before the run, follow¬ing an overnight fast, each participant consumed a high GI (GI = 70) or a low GI (GI = 37) breakfast meal or performed the trial in a fasting state (FAST). Each trial consisted of a 60-minute run at 70% heart rate reserve on a motorized treadmill. Plasma glucose was measured at fast, at each 15-minute postprandial, and during the exercise period. Ratings of perceived exertion, stomach fullness, thirsty sensation and blood pressure were recorded. Results: Following ingestion of high- and low-GI meals, plasma glucose concentrations increased in both trials and peaked at 15 minutes during the postprandial period (8.3 ± 1.2 mmol.L-1 and 7.6 ± 0.8 mmol.L-1, respectively). At 15 minutes of exercise, plasma glucose decreased below fasting values in both breakfast trials and was significantly lower (P < 0.05) than in FAST. Plasma glucose was not different between trials after 15 minutes of exercise. There were no differences in physiologic and self-reported parameters during exercise among the trials.Conclusions: We conclude that one-hour running in a fasting state or following a 60-minute rest after high or low GI meal ingestion does not cause hypoglycemia or anticipate fatigue in non-athletes.
Authors and Affiliations
Janaína Altoé, Rafael da Silva, Guilherme Artioli, Rita de Cássia Alfenas, Valéria de Faria, Lawrens Cardozo Makkai, João Bouzas Marins
Keywords
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