Comparing the immunological and physiological effects between high-intensity interval training and moderate-intensity continuous training in physically inactive adults

Introduction: High-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) are effective exercise methods for enhancing fitness and health in healthy individuals. However, research on their impact on immune responses and bone metabolism in physically inactive adults is limited. Objective: To investigate the effects of HIIT and MICT on immune responses, bone metabolism markers and selected physiological parameters in physically inactive adults. Methodology: Thirty-six physically inactive adults aged 18 to 35 were randomly assigned to HIIT, MICT, or control groups (n=12 each). The HIIT group performed 2 sets of 6-8 repetitions of 30 seconds of running at 85-95% of estimated HRmax, three times a week. The MICT group ran for 30 minutes at 55-70% of estimated HRmax, three times a week, while the control group did not exercise. Maximum oxygen consumption (VO2max), blood, and saliva samples were collected before and after an 8-week intervention. Results: Both HIIT and MICT significantly increased salivary lysozyme levels compared to baseline (p < 0.05), but no significant differences were found between groups (p > 0.05). Total leukocyte counts and bone metabolism markers showed no significant changes across groups. Maximum oxygen consumption improved only in the HIIT group (p < 0.05). Discussion: The immune response’s enhancement following HIIT and MICT may be attributed to hormonal changes resulting from the production of free radicals during strenuous exercise. Conclusions: Both HIIT and MICT enhance immune responses without affecting bone metabolism markers. HIIT appears to be more effective than MICT for improving VO2max in physically inactive adults.