The time course of musculotendinous stiffness responses following different durations of passive stretching.

Abstract

Repeated-measures experimental design. 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. Stretching is often implemented prior to exercise or athletic competition, with the intent to reduce the risk of injury via decreases in MTS. Twelve subjects (mean +/- SD age, 24 +/- 3 years; stature, 169 +/- 12 cm; mass, 71 +/- 17 kg) participated in 4 randomly-ordered experimental trials: control with no stretching, 2 minutes (2min), 4 minutes (4min), and 8 minutes (8min) 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. MTS decreased (P<.05) immediately after all stretching conditions (2min, 4min, and 8min). However, MTS for the 2min condition returned to baseline within 10 minutes, whereas MTS after the 4min and 8min passive-stretching conditions returned to baseline within 20 minutes. Practical durations of passive stretching resulted in significant decreases in MTS; however, these changes return to baseline levels within 10 to 20 minutes.