Comparison Between High- and Low-Intensity Static Stretching Training Program on Active and Passive Properties of Plantar Flexors

The purpose of this study was to compare two static stretching (SS) training programs at high-intensity (HI-SS) and low-intensity (LI-SS) on passive and active properties of the plantar flexor muscles. Forty healthy young men were randomly allocated into three groups: HI-SS intervention group (n = 14), LI-SS intervention group (n = 13), and non-intervention control group (n = 13). An 11-point numerical scale (0-10; none to very painful stretching) was used to determine SS intensity. HI-SS and LI-SS stretched at 6-7 and 0-1 intensities, respectively, both in 3 sets of 60 s, 3x/week, for 4 weeks. Dorsiflexion range of motion (ROM), gastrocnemius muscle stiffness, muscle strength, drop jump height, and muscle architecture were assessed before and after SS training program. The HI-SS group improved more than LI-SS in ROM (40 vs. 15%) and decreased muscle stiffness (-57 vs. -24%), while no significant change was observed for muscle strength, drop jump height, and muscle architecture in both groups. The control group presented no significant change in any variable. Performing HI-SS is more effective than LI-SS for increasing ROM and decreasing muscle stiffness of plantar flexor muscles following a 4-week training period in young men. However, SS may not increase muscle strength or hypertrophy, regardless of the stretching discomfort intensity.

Automated summary

High-intensity static stretching (HI-SS) is more effective than low-intensity (LI-SS) for increasing range of motion and decreasing muscle stiffness of the plantar flexor muscles in young men after a 4-week training period. However, neither HI-SS nor LI-SS training led to changes in muscle strength, jump height, or muscle architecture. The control group did not show significant changes in any variables.