Acute changes in passive stiffness and range of motion post-stretching

Purpose: To investigate the change in passive hamstring stiffness and knee joint range of motion (ROM) following a single bout of passive hamstring stretching with or without active movement post-stretch. Methods: A Kincom dynamometer was used to measure knee joint ROM and passive stiffness in nine participants. Each participant completed three conditions: (1) a baseline test of knee extension ROM and passive stiffness, 4 x 20 second static stretches of the hamstring muscles and repeat testing immediately post-stretch and at 5 min intervals for 20min; (2) the same procedure with the addition of 90 s of isotonic knee flexion and extension between tests over the 20 min post-stretching period; (3) the control condition involving repeat tests only over20 min. Results: Knee joint ROM increased by 4-5 degrees post-stretch in both intervention conditions, relative to the control condition, but there was no clear evidence of the ROM increase lasting longer than 5 min. Both intervention conditions showed a small decrease in passive stiffness post-stretch and it is likely this effect lasted for at least 20min. Conclusions: An isolated bout of stretching produced a small, short-lived change in ROM and stiffness. This has implications for the design of warm-up protocols. (c) 2006 Elsevier Ltd. All rights reserved.