The Effects of Speed with Dynamic Stretching on Musculotendinous Stiffness

Dynamic stretching (DS) comprises repetitive movements throughout the joint range of motion, and DS speed is known to affect athletic performance. However, it is unclear how DS speed affects musculotendinous stiffness (MTS). This study aimed to compare the DS effects at three different speeds on the maximum ankle dorsiflexion angle, maximum passive torque, and MTS. Based on sample size calculation (f = 0.25, α = 0.05, power = 0.80), 12 participants were needed, and 12 healthy university male athletes enrolled. DS to ankle plantar flexors was performed under the following conditions: low-speed (30 reps/min), moderate-speed (60 reps/min), high-speed (120 reps/min), and control (no DS). DS was performed for 15 reps × four sets with a 30 s rest. To assess musculotendinous extensibility, the maximum ankle dorsiflexion angle, maximum passive torque, and MTS were measured before and after DS. The maximum ankle dorsiflexion angle significantly increased after all DS (p = 0.001–0.006, dz = 0.98–1.38) and was significantly larger in the high-speed DS than in the control condition (p = 0.039). MTS significantly increased after high-speed DS (p = 0.038, d = 0.68) but significantly decreased after moderate-speed DS (p = 0.025, dz = −0.75) compared to baseline values. Maximal passive torque significantly increased after low-, moderate-, and high-speed DS (p < 0.001 to p = 0.011, dz = 0.89–1.89) and was significantly higher after high-speed DS than after control (p = 0.004, d = 0.58). These results indicate that DS increases the ankle dorsiflexion angle regardless of speed and is effective in decreasing MTS at moderate speed.