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Friday, December 10, 2010

For Pure Flexibility, Static Stretching Beats Dynamic Stretching

This blog contains several articles that have shown that static stretching impairs physical performance in jumping, running, and team sports, when the stretching is done immediately prior to the effort. Dynamic stretching has not been shown to cause a similar impairment and may even enhance performance. Yet, this finding does not mean that dynamic stretching is superior to static stretching for all purposes. Indeed, a study published by Covert et al. in the Journal of strength and Conditioning Research (vol. 24, no. 11, pp. 3008-3014, 2010) indicates that static stretching is better for improving pure flexibility.

Study Procedures
Over a 4-week period, 16 men and 16 women, aged 20-27 were randomly divided into the following 3 groups:
Static Stretching: Held a stretched position of the hamstring muscles for 30 seconds 3 times a week
Dynamic Stretching: Got into a stretched position of the hamstring muscles then performed small bounces into and out of that position at a rate of 1 per second for 30 seconds, 3 times a week
Control: Did not stretch
Hamstring flexibility was measured as the number of degrees short of 180 degrees that the knee could be extended to while the subject lay on a table with the thigh in a vertical position. Thus, a smaller number of degrees indicated better flexibility.

The differences between changes in hamstring flexibility among all three groups were statistically significant
The control group declined by a mean of 3.3 degrees in hamstring flexibility
The static stretching group improved a mean of 11.9 degrees in hamstring flexibility
The dynamic stretching group improved a mean of 3.8 degrees in hamstring flexibility

Bottom Line
Either form of stretching improves flexibility. However, static stretching improves flexibility significantly more than does dynamic stretching. For sports in which flexibility in not very important, dynamic stretching is best. However, for sports which require a lot of flexibility (e.g. gymnastics, wrestling, high-hurdles) some static stretching is advisable. But because static stretching impairs performance when done immediately prior to the sport activity, it is best to do such stretching immediately following a training session, when the muscles are well warmed up. The impairment in performance caused by static stretching has not been found to carry over to the following day, so post-exercise static stretching should not impair a subsequent day's performance.

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