The Comparative Effects of Isometric and Isotonic Leg Exercises on Female Students’ Vertical Jump Height in a Physical Education Setting

Abstract

Vertical jump height is a key indicator of lower-body explosive strength and is essential for performance in sports requiring rapid take-off; however, female adolescents consistently demonstrate lower jump performance than males due to physiological, neuromuscular, and training-related factors. In Philippine public schools, physical education programs commonly rely on low-equipment, bodyweight exercises—particularly isotonic and isometric modalities—yet comparative evidence regarding their effectiveness for improving vertical jump height remains limited. Guided by Hatfield's Strength Continuum Theory and the Stretch–Shortening Cycle model, this quasi-experimental study compared the effects of isotonic and isometric leg exercises on the vertical jump height of Grade 8 female students in a public high school in Misamis Oriental, Philippines. Using a pretest–posttest non-equivalent groups design, 38 participants (19 per group) completed an 8-week intervention consisting of two sessions per week with identical time allotment (40–45 minutes per session) and equivalent training frequency and overall intensity, differing only in the type of muscle contraction performed. The isotonic group engaged in dynamic exercises such as squats, lunges, and leg curls, while the isometric group performed static holds including wall sits, glute bridge holds, and calf raise holds. Vertical jump height was assessed using the Sargent Chalk Jump Test. Descriptive statistics summarized performance profiles, paired-samples t-tests examined within-group changes, and ANCOVA compared posttest outcomes while controlling for baseline differences. Results indicated significant pre-to-post improvements in both the isometric group (t(18) = −6.156, p < .001, Cohen's d = 1.41) and the isotonic group (t(18) = −6.356, p < .001, Cohen's d = 1.46), with large effect sizes in both cases. However, no significant between-group difference was observed after adjustment for baseline scores (F(1,35) = 0.442, p = .511, partial η² = 0.012), indicating that isotonic and isometric exercises were comparably effective when matched for frequency, duration, and training load. These findings support the use of either modality in school-based physical education programs, particularly in low-resource settings.