Physiological Responses to Sprint Interval Exercise in a Fasted State in Active Men

Introduction: Fasting is a method used to enhance metabolic flexibility toward lipid utilization. However, there are concerns about hypoglycemia or protein breakdown in exercise. The present study investigated the physiological responses to sprint interval exercise with different rest durations in a fasting state. Methods: For this randomized crossover study, ۱۰ healthy active men (aged ۲۲.۷۰ ± ۱.۱۵) were selected from eligible volunteers. In ۲ separate sessions, following ۱۴ hours of fasting, participants randomly performed ۵×۱۵s all-out sprints on an E۸۹۴ MONARK ergometer with ۳۰ or ۶۰s rest intervals. Results: Diastolic blood pressure and heart rate were lower with longer rest intervals. Blood glucose, insulin, and urea remained unchanged after both protocols compared with baseline levels. There was a marked increase in lactate levels after both protocols, independent of the rest duration. The immune response was significantly higher with longer rest intervals than with short rest intervals or baseline levels. Conclusion: Sprint interval exercise performed in a fasted state did not induce hypoglycemia or evidence of protein degradation, suggesting that such training may be safe for active men. Longer rest intervals were associated with lower post-exercise heart rate and diastolic blood pressure, as well as an enhanced immune response. These findings suggest that coaches and practitioners may consider manipulating rest intervals to achieve targeted physiological adaptations.

کلیدواژه ها:

Exercise intensity ، Overnight fasting ، hypoglycemia ، Immune response ، Protein degradation