Effect of High-Intensity Interval Training and unification training on Aerobic Capacity and Muscle Strength in Intermediate Distance Runners- a systematic review

Introduction and Objectives: Aerobic capacity and muscular strength are two important physical components that influence the performance of middle-distance runners. High-intensity interval Training (HIIT) and unification training have been recognized as effective methods for improving these parameters. However, scientific evidence comprehensively examining the effects of these two methods on middle-distance runners is limited. Therefore, this study aimed to systematically evaluate the impact of HIIT and unification training on the aerobic capacity and muscle strength of middle-distance runners. Methodology: This study was a systematic review that followed the PRISMA guidelines. Data were obtained from PubMed, Scopus, and Google Scholar databases with inclusion criteria including experimental studies published in the last 10 years. A total of 20 articles were selected and analyzed qualitatively. The main parameters evaluated were changes in aerobic capacity (VO₂max) and muscle strength (dynamic and isometric) in middle-distance runners. Results: This review found that HIIT significantly improved aerobic capacity through cardiovascular adaptation and oxygen efficiency. Unification training, which combines aerobic and strength components, showed significant improvements in muscle strength, especially in the lower limb muscles. Several studies have shown that combining HIIT and unification training synergistically affects both parameters. Conclusion: HIIT and unification training improves aerobic capacity and muscular strength in middle-distance runners. The combination of both methods provided more optimal results. The practical implication is that coaches and athletes can adopt an integrated training approach to optimize performance. Further research is needed to explore the most effective exercise duration and intensity.