Effects of short-duration constant torque and constant angle stretching on the musculotendinous stiffness of ankle plantar flexors

Purpose This study investigated the time-course changes in the four sets of 30 s constant torque stretching (CTS) and constant angle stretching (CAS) on musculotendinous stiffness (MTS) of the ankle plantar flexors. Methods Employing a crossover design, this study included 21 healthy young males who underwent CTS and CAS in a randomized order. Each stretching condition comprised four sets of 30 s stretches separated by 20 s rest intervals. MTS was measured using torque-angle curves before and after each set. Results Two-way repeated-measures analysis of variance (ANOVA) revealed a significant interaction effect between the stretching condition and time on MTS (p = 0.03). While both CTS and CAS significantly reduced MTS after each set, greater reductions were observed in CTS across all sets. Conclusion This study suggests that CTS is an effective stretching technique for significantly reducing the MTS of ankle plantar flexors within a short duration of time, indicating its utility in warm-up exercises and rehabilitation programs.