Much of the recent research has suggested that it is best to warm-up prior to exercise to decrease risk of injury, deviating from the previously accepted practice of stretching. Mike Reinold's recent post discussed some of the disparities between the more recent and older research on the topic. One of the major factors brought up is that stretching less than 30 seconds is not associated with increased injury risk. In fact, stretching longer than 30 seconds is okay as well if combined with some form of dynamic exercise. The question of "why" arises. As we've discussed before, a stretch only changes tissue length after 30 seconds of static hold. In school, we were taught that when stretching, we should proceed to strengthen in the newly acquired range. This is important so that we can maintain that range and have control over the joint. Without strengthening/neuromuscular training in the new range, the joint loses stability. We really shouldn't be trying to increase muscle length prior to any competition, especially since the muscles/joints are weak at those points. Our theory is that stretching less than 30 seconds or combining stretching with dynamic exercises activates or maintains some neuromuscular tone/reflex that protects the joint in end range by decreasing perceived stiffness. Fatigue has been shown to play a role in stretch reflex inhibition, thus decreasing performance (Ross et al, 2001). Just as concerning, prolonged passive stretches have been shown to an effect on the tendinous tissue, such as stress relaxation and plastic deformation (Avela et al, 2004). By keeping stretches under 30 seconds or adding dynamic exercises, this protective reflex is not lost. Many PT schools teach that ballistic stretching can be hazardous to the tissue, but with these findings, do you think that type of exercise actually does have a role in performance enhancement/injury prevention?
Avela J, Finni T, Liikavainio T, Niemelä E, Komi PV. (2004). Neural and mechanical responses of the triceps surae muscle group after 1 h of repeated fast passive stretches. J Appl Physiol. 2004 Jun;96(6):2325-32. Web. 11 Aug 2013.
Avela J, Kyröläinen H, Komi PV. (1999). Altered reflex sensitivity after repeated and prolonged passive muscle stretching. J Appl Physiol. 1999 Apr;86(4):1283-91. Web. 11 Aug 2013.
Chalmers G. (2004). Re-examination of the possible role of Golgi tendon organ and muscle spindle reflexes in proprioceptive neuromuscular facilitation muscle stretching. Sports Biomech. 2004 Jan;3(1):159-83. Web. 11 Aug 2013.
Ross A, Leveritt M, Riek S. (2001). Neural influences on sprint running: training adaptations and acute responses. Sports Med. 2001;31(6):409-25. Web. 11 Aug 2013.