High-Intensity vs. Moderate-Intensity Interval Training and Effects on Stress

HIIT vs MIIT on Stress Biomarkers

Abstract

ABSTRACT

Objective: High-Intensity Interval Training (HIIT) may elicit greater endocrine and sympathetic responses than moderate-intensity interval training (MIIT), resulting in different outcomes. The study explores the acute impact of HIIT and MIIT  on salivary cortisol, heart rate variability, and state anxiety in young, healthy adults.

Study design: A single visit randomized trail.

Place and duration of study: Khyber Medical University

Patients and Methods: A total of fifty participants were randomly allocated to either the HIIT group or the MIIT group. Each group consisted of twenty-five participants. The pre- and post-exercise assessments included salivary cortisol, HRV parameters (RMSSD, SDNN, and LF/HF ratio), and the STAI-State Anxiety scale. The participants completed a single bout of exercise at either high or moderate intensity.

Results: A significant increase in salivary cortisol levels was found in the HIIT group, whereas a slight decrease in cortisol levels was found in the MIIT group. The cortisol levels increased significantly in the HIIT group, i.e., 0.27 to 0.36 µg/dL, which is a 32.8% increase, whereas the cortisol levels decreased slightly in the MIIT group, i.e., 0.26 to 0.24 µg/dL, which is a 9.3% decrease. Analysis of HRV parameters revealed that the HIIT group had decreased values in the RMSSD and SDNN parameters and increased values in the LF/HF parameter, indicating increased sympathetic activity.

Conclusion: In contrast, HIIT elicits a strong physiological stress reaction with increased cortisol and sympathetic nervous system dominance. MIIT elicits parasympathetic nervous system activation and has greater anxiolytic effects. These results indicate that MIIT might be more appropriate for stress reduction, while HIIT might be useful as a physiological stressor in conditioning. Exercise prescriptions should be based on the stress profile of individuals and the outcome.