Abstract
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, 3×/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.
Highlights
Static stretching (SS) interventions are generally performed in sports and rehabilitation settings to improve a variety of fitness- and health-related capacities
The post hoc test showed that the DF range of motion (ROM) was increased in both HI-static stretching (SS) and LI-SS groups (p < 0.01, d = 0.92; p = 0.03, d = 0.33), and the relative change ( %) in the dorsiflexion ROM (DF ROM) in the HI-SS group ( % = 46.5 ± 35.8) was significantly higher than the LI-SS group ( % = 15.8 ± 15.5, p = 0.028, d = 1.20)
We showed that both HI-SS and LI-SS training programs increased the DF ROM and decreased muscle stiffness, results were significantly larger for HI-SS
Summary
Static stretching (SS) interventions are generally performed in sports and rehabilitation settings to improve a variety of fitness- and health-related capacities. Among the factors that have explained the differences between results in the literature, the main one refers to the variety of characteristics of the SS programs; type, volume, and intensity of the stretching exercises. The exercise intensity has been proposed as a major factor that affects the effectiveness of SS programs (Apostolopoulos et al, 2015; Nunes et al, 2020b). Previous studies focusing on the acute effects of stretching intensity indicate larger increases in ROM and decreases in passive stiffness of the hamstring muscles for high-intensity SS than normal intensity SS (Fukaya et al, 2020b; Takeuchi and Nakamura, 2020a; Takeuchi et al, 2021a,b,c). Highintensity SS intervention seems to be effective in immediately increasing ROM and decreasing passive stiffness
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