Effects of Whole-Body HIIT and Moderate Continuous Exercise on Immune Function

This study was designed as a two-arm, parallel-group, randomized controlled trial. A total of 20 recreationally active male participants were randomly assigned to either the Whole Body High-Intensity Interval Training (WB-HIIT) group or the Moderate-Intensity Continuous Training (MICT) group. The intervention lasted 12 weeks and involved supervised training sessions multiple times a week.

The WB-HIIT protocol consisted of repeated high-intensity whole-body exercises performed at near-maximum effort with intermittent rest periods, while the MICT group performed moderate-intensity continuous aerobic exercise. Immune function was assessed through selected hematological and biochemical markers collected at baseline and post-intervention. In addition, physical performance variables were evaluated to examine secondary adaptations to different exercise modalities. The primary aim of the study was to compare the effects of WB-HIIT and MICT on immune system responses, while secondary outcomes included changes in exercise performance. This study provides insights into how different training intensities affect immune regulation in individuals who are active in their leisure time.

• Whole-Body High-Intensity Interval Training (WB-HIIT) (Behavioral): Whole-body high-intensity interval training protocol performed under supervision.
• Moderate-Intensity Continuous Training (MICT) (Behavioral): Moderate-intensity continuous training protocol performed under supervision.

Primary outcomes

• Peripheral immune cell counts [Baseline and 8 weeks (post-intervention)]: Changes in peripheral blood leukocyte, lymphocyte subsets, neutrophil, and monocyte counts from baseline to post-intervention (8 weeks).

Secondary outcomes

• Inflammatory cytokine levels [Baseline and 8 weeks (post-intervention)]: Changes in serum IL-6, TNF-α, and CRP levels from baseline to post-intervention (8 weeks).
• Immunoglobulin levels [Baseline and 8 weeks (post-intervention)]: Changes in serum immunoglobulin (IgA, IgG, IgM) concentrations from baseline to post-intervention (8 weeks).
• Cortisol levels [Baseline and 8 weeks (post-intervention)]: Changes in serum cortisol levels as a marker of exercise-induced stress response from baseline to post-intervention (8 weeks).
• Maximal oxygen uptake (VO₂max) [Baseline and 8 weeks (post-intervention)]: Changes in VO₂max measured by cardiopulmonary exercise testing from baseline to post-intervention.

Sex: Male, ages: 18 Years to any, accepts healthy volunteers

Inclusion Criteria:

Healthy male adults Aged 18-25 years Not engaged in regular structured exercise training (>3 sessions/week) VO₂max within normal healthy range Willingness to participate and provide informed consent No acute or chronic inflammatory, metabolic, or cardiovascular disease

Exclusion Criteria:

Female participants (not included in study design) Smoking or alcohol abuse Use of anti-inflammatory or immunomodulatory drugs Participation in regular high-intensity training programs Musculoskeletal limitations preventing exercise testing or training Acute infection within last 2 weeks Chronic metabolic, cardiovascular, or autoimmune diseases

• Study Protocol (PDF, 2026-05-16)

• Melih Çalışır, PhD, Principal investigator, Bitlis Eren Üniversitesi University