Comparison of the Effects of a Single-Session and Multi-Session Iso-Volume High-Intensity Interval Training on Changes in Selected Physical Fitness Components in Professional Athlete

Rajabi, Hamid; Khalili, Hojjat Allah; Motamedi, Pezhman; Saremi, Abbas

doi:10.22089/spj.2026.19492.2454

Comparison of the Effects of a Single-Session and Multi-Session Iso-Volume High-Intensity Interval Training on Changes in Selected Physical Fitness Components in Professional Athlete

Articles in Press

Document Type : Research Paper

Authors

Hamid Rajabi ¹

Hojjat allah Khalili ²

Pezhman Motamedi ²

Abbas Saremi ³

¹ Professor of Sport Physiology, Kharazmi University

² Kharazmi University, Faculty of Physical Education and Sport Sciences, Department of Exercise Physiology

³ Arak University, Faculty of Physical Education and Sport Sciences, Department of Exercise Physiology

10.22089/spj.2026.19492.2454

Abstract

**Objective:** This study compared the effects of four weeks of volume-matched single-bout and multi-bout high-intensity interval training (HIIT) on physical fitness in professional athletes, as the impact of multi-bout training in elite populations remains underexplored.

**Methods:** Twenty handball and basketball players (mean age: 21 years) were randomly assigned to single-bout (n = 10) or multi-bout (n = 10) HIIT groups. Training was performed three times per week for four weeks. The single-bout group completed three 6-minute HIIT blocks in one session, while the multi-bout group performed the same workload across three daily sessions separated by 4-hour intervals. Aerobic capacity, sprint performance, agility, muscular strength and endurance, vertical jump, and Hooper Index were assessed pre- and post-intervention using repeated-measures ANOVA.

**Results:** Both groups showed significant improvements in aerobic capacity, muscular strength, and muscular endurance. No significant changes were observed in sprint performance, agility, or vertical jump. The multi-bout group showed more favorable, though non-significant, improvements in Hooper Index scores, including reduced fatigue, stress, and muscle soreness, and better sleep quality.

**Conclusion:** Both HIIT protocols effectively improved key fitness variables, while multi-bout training may provide additional benefits in recovery and training load management for professional athletes.

Keywords

High-Intensity Interval Training

Exercise Snacks

Physical Fitness

Hooper Index

Professional Athletes

Muscle Endurance,

Subjects