The Time Course of Musculotendinous Stiffness Responses Following Different Durations of Passive Stretching

STUDY DESIGN: Repeated-measures experimental design. OBJECTIVE: To examine the acute effects of different durations of passive stretching on the time course of musculotendinous stiffness (MTS) responses in the plantar flexor muscles. BACKGROUND: Stretching is often implemented prior to exercise or athletic competition, with the intent to reduce the risk of injury via decreases in MTS. METHODS AND MEASURES: Twelve subjects (mean +/- SID age, 24 +/- 3 years; stature, 169 +/- 12 cm; mass, 71 +/- 17 kg) participated in 4 randomly ordered experimental trials: control with no stretching, and 2 minutes (2(min)), 4 minutes (4(min)), and 8 minutes (8(min)) of passive stretching. The passive-stretching trials involved progressive repetitions of 30-second passive stretches, while the control trial involved 15 minutes of resting. MTS assessments were conducted before (prestretching), immediately after (poststretching), and at 10, 20, and 30 minutes poststretching on a Biodex System 3 isokinetic dynamometer. RESULTS: MTS decreased (P < .05) immediately after all stretching conditions (2(min), 4(min), and 8(min)). However, MTS for the 2(min) condition returned to baseline within 10 minutes, whereas MTS after the 4(min) and 8(min) passive-stretching conditions returned to baseline within 20 minutes. CONCLUSIONS: Practical durations of passive stretching resulted in significant decreases in MTS; however, these changes return to baseline levels within 10 to 20 minutes. LEVEL OF EVIDENCE: Level 5. J Orthop Sports Phys Ther2008;38(10):632-639. doi:10.2519/jospt.2008.2843