The effects of 4 weeks stretching training to the point of pain on flexibility and muscle tendon unit properties.

Abstract

The purpose of this study wasto compare the benefits and possible problems of 4weeks stretching when taken to the point of pain (POP) and to the point of discomfort (POD). Twenty-six physically active women(20±1.1years)took part in group-based stretching classes of the hamstring muscles, 4 times per week for 4weeks, one group onestretching to POD, the other to POP. Passive stiffness, joint range of motion (ROM), maximal isometric torque and concentric knee flexion torque, were measured before training and 2days after the last training session. Hip flexion ROMincreased by 14.1° (10.1°-18.1°) and 19.8° (15.1°-24.5°) and sit-and-reach by 7.6 (5.2-10.0) cm and 7.5 (5.0-10.0) cm for POD and POP, respectively (Mean and 95% CI; p<0.001 within group; NS between groups), with no evidence of damage in either group. Despite the large increases in flexibility there were no changes in either compliance or viscoelastic properties of the muscle tendon unit (MTU). Hamstrings stretching to POP increased flexibility and had no detrimental effects on muscle function but the benefits were no better than when stretching to POD so there is no justification for recommending painful stretching. The improvements in flexibility over 4weeks of stretching training appear to be largely due to changes in the perception of pain rather than physical properties of the MTU although less flexible individuals benefited more from the training and increased hamstring muscle length.