Introduction: After consuming carbohydrates (OH) before exercise, an increase in OH oxidation is observed, along with a decrease in the availability of free fatty acids in the plasma and a reduction in lipid oxidation during exercise. Consuming OH 30 to 60 minutes before exercise can cause hyperglycemia and hyperinsulinemia at the onset of exercise, followed by a rapid decrease in blood glucose concentration, known as transient hypoglycemia. Nevertheless, it appears that there is no reason to avoid consuming OH before exercise, as no adverse effects on performance have been observed. Purpose: The aim of this thesis was to determine how a OH meal consumed 30 minutes before incremental exercise to exhaustion (SSVI) affects subcutaneous glucose concentration, substrate utilization and respiratory quotient during exercise, and to determine whether there is a correlation between subcutaneous glucose concentration and respiratory quotient. Methods: The study involved 10 healthy young subjects (6 females, 4 males). Each participant completed 2 SSVI tests on a stationary bike. One test was performed in a fasted state, and the other 30 minutes after consuming a OH meal. During the measurement period, participants wore a glucose sensor to monitor subcutaneous glucose concentration before, during, and after the SSVI. Data was appropriately evaluated and statistically processed. Results: The highest increase in subcutaneous glucose concentration (pGLK) in the OH meal trial was measured 15 minutes after meal consumption (6.9 ± 0.6 mmol/l), followed by a decrease (4.6 ± 0.8 mmol/l at 30 minutes) and fell below fasting pGLK values. The respiratory quotient was significantly different in the SSVI after the OH meal compared to the fasted SSVI during the resting phase (p=0.001), at 40% V ̇O2maks (p=0.009), 60% V ̇O2maks (p=0.05), and 80% V ̇O2maks (p=0.018). Discussion and Conclusion: The results of this study show that a preexercise OH meal switches the metabolism to a higher OH consumption during exercise. Conversely, the proportion of energy obtained through the oxidation of free fatty acids increases during fasting exercise. Fasting exercising could therefore represent a training strategy for reducing body fat reserves. This metabolic shift can be directly influenced by a higher blood glucose level or by a higher blood insulin concentration, both of which rise sharply after an OH meal. Further studies could investigate the effects of an OH meal before training on physical performance.
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