Viscoelasticity of the muscle-tendon unit is returned more rapidly than range of motion after stretching.
Mizuno T, Matsumoto M, Umemura Y. Scand J Med Sci Sports. 2011 May 12. doi: 10.1111/j.1600-0838.2011.01329.x. [Epub ahead of print]
Static stretching is one of the most common injury prevention techniques used in athletics, both competitive and recreational. It has been shown to have acute benefits like increased range of motion (ROM) and decreased stiffness of the muscle-tendon unit. Chronic stretching has also been studied and found to have benefits. All of these benefits are thought to minimize stress on the joint and muscle-tendon unit and therefore decrease the risk of injury. However, the duration of these benefits following acute stretching have never been examined. Therefore, this study examined the displacement of the myotendinous junction, passive end ROM, and passive torque of the gastrocnemius medialis muscle in 11 healthy participants (average age 23 years) following an acute bout of static stretching to determine the duration of beneficial effects. These characteristics were measured before stretching as well as 0, 15, 30, 60, and 90 minutes following stretching. During the time point participants remained in a seated position. Stretching consisted of passive dorsiflexion to the end ROM which was held for 1 minute and repeated 5 times. They found that after stretching passive end ROM significantly increased at 0, 15, and 30 minutes but not at the 60 or 90 minute time point compared to pre-stetching. Passive torque at end ROM was also increased after stretching. Stiffness was found to be significantly decreased immediately after stretching however stiffness was similar to pre-stretching by 15 minutes post-stretching.
This study provides additional information to clinicians for the benefits of stretching but also raises additional questions. Static stretching is thought to decrease injuries by decreasing tissue stiffness and increasing ROM. Previously this was thought to be maintained for extended periods of time during activity. These results suggest that only ROM is sustained overtime and muscle-tendon unit stiffness is not. This raises some interesting questions clinically. Which is more important in preventing injuries: ROM or stiffness? Do these characteristics contribute to reducing injury rates at all? The sustained increase in ROM could potentially help to minimize injuries by dissipating force over a greater ROM and time. This study found that it only lasted 30 minutes however these participants remained seated during that period. Therefore, walking or running may help to further maintain the increase in ROM and stiffness. This would be a nice follow-up study. One methodology issue is that muscle-tendon stiffness was calculated by the displacement of the myoteninous junction and the torque during passive motion. However, this torque is caused by the entire ankle joint, not just the gastrocnemius. Therefore, the stiffness is not specific to the muscle-tendon unit but the whole ankle joint. As clinicians we are continually searching for validity to the treatments we used every day. This study is a nice addition to the knowledge about static stretching and how long the beneficial effect can be maintained. However, additional research is required. What are your thoughts on these results? Do you feel static stretching is an important part of injury prevention? Do you feel its joint specific?
Written by: Stephen Thomas
Reviewed by: Jeffrey Driban