Effects of a high-volume static stretching programme on plantar-flexor muscle strength and architecture

Purpose Static stretching (SS) is performed in various settings, but there is no consensus about the effects of SS programmes on changes in muscle morphofunction. This study aimed to investigate the effects of a high-volume SS programme on muscle strength and architecture. Methods Sixteen healthy young male adults participated, and the dominant leg was defined as the intervention side, with the non-dominant leg as the control side. Stretching exercises were performed two times per week (6 sets of 5 min, totally 30 min per session,) for 5-week using a stretching board under the supervision of the research team. Before and after SS intervention programme, plantar-flexor strength (maximum voluntary isometric contraction, MVC-ISO; maximum voluntary concentric contraction, MVC-CON) and architecture (muscle thickness, pennation angle, and fascicle length) were measured via dynamometer and ultrasound, respectively. Results Following the SS-training programme, significant increases were observed for stretching side in MVIC-ISO at neutral ankle position (p = 0.02, d = 0.31, Delta = 6.4 +/- 9.9%) and MVC-CON at 120 degrees/s (p = 0.02, d = 0.30, Delta = 7.8 +/- 9.1%), with no significant change on the control side. There was no significant change in any measure of muscle architecture for both intervention and control sides. Conclusion Five-week high-volume SS induced positive changes on some measures of muscle strength but not hypertrophy of plantar-flexor muscles. Even with a volume much greater than already tested, the low strain offered by the SS per set seems be insufficient to induce architectural changes on skeletal muscle.