Direct relation of acute effects of static stretching on isokinetic torque production with initial flexibility level.

Purpose: To examine the acute effect of a single static-stretching session of hamstring muscles on torque production in relation with individual flexibility.
Methods: Maximal voluntary concentric torque of hamstring muscles was measured before and after a static-stretching session (6 × 30 s). Torque changes were correlated with the flexibility level determined at the onset of the experimental procedure.
Results: The hamstring-stretching intervention significantly reduced maximal concentric torque in participants with low and high hamstring flexibility. Hamstring flexibility and torque decrease, determined immediately after the stretching procedure, were negatively correlated.
Conclusions: Torque decrease measured after the static-stretching session is dependent on participant flexibility. Participants with low flexibility are much more likely to demonstrate large torque decreases poststretching.