Stretching Revisited

Recently, a New York Times article summarized some research by the University of Nevada that concluded that static stretching for 30 seconds decreased muscular power of the hamstring and quadricep muscles of those that stretched before activity versus those that did not.1 The decrease was about 3%, minimal but not insignificant, particularly when fractions of a second can count in sprinting events. Vertical jumping height and torque were unchanged. Power is the application of work within a finite time. Torque is the application of force and does not require movement unlike work. Torque is the force you apply to a jam jar that is stuck. Work is what happens once you get the lid moving.. Similar reductions were found in the Achilles tendon in a previous study.2 Two other studies reported that strength was reduced up to one hour after static stretching.3

It is important to remember that athletes have different requirements depending on the sport and stretching should be sport specific. "Athletes typically include static stretching as a part of the warm-up, but the evidence is clear that this practice will decrease performance in sports that require explosive movements," said UNLV kinesiology professor and study co-author Bill Holcomb, who directs the university's Sports Injury Research Center. When I asked Bill Holcomb to elaborate on his conclusions he said “The type of stretching to warmup should be dynamic rather than static to prevent a reduction of power. Then, after activity and during the cool down, static stretching can be used to improve range of motion/flexibility for later performance.“ Warming up is also something that can be overdone at the expense of performance.

“There is a neuromuscular inhibitory response to static stretching,” says Malachy McHugh, the director of research at the Nicholas Institute of Sports Medicine and Athletic Trauma at Lenox Hill Hospital in New York City. The straining muscle becomes less responsive and stays weakened for up to 30 minutes after stretching. Another support to the idea of the inhibitory response is that the other side of the stretched leg has been shown to have less power. Stretching muscles while moving, on the other hand, a technique known as dynamic stretching or dynamic warm-ups, increases power, flexibility and range of motion. Muscles in motion don’t experience the inhibitory response. They instead get what McHugh calls “an excitatory message” to perform.

Much has been written about problems with ballistic stretching but dynamic stretching is different. Dynamic stretching consists of controlled leg and arm movements that extend to the limits of your range of motion. Ballistic stretches involve trying to force a part of the body beyond its range of motion. In dynamic stretches, there is no bouncing.
Flexibility is speed specific. There are two kinds of stretch receptors, one measures magnitude and speed and the other measures magnitude only. These receptors are also responsible for the stretch reflex, our body’s protective mechanism, which counters in the opposite direction to the part being stretched. This also explains why it doesn’t make sense to static stretch prior to dynamic activity. There is considerable but not complete transfer of static stretching to dynamic stretching.4 In another study that looked at static stretching done not in close proximity to testing, on groups that were doing no other training regimen, the stretching group performed better. The author concluded that stretching in this manner could help bridge to a regular training regimen.5

Citing earlier studies, Stacy Ingraham, an exercise physiologist at the University of Minnesota, Twin Cities, says that, "When you stretch, you lengthen muscle fibers. It then takes longer for messages from the brain to travel through them. Stretched muscles also seem to be more sluggish than un-stretched ones. They don't spring back as readily. And every time you stretch, you may be tearing your muscle fibers a tiny bit."

The epidemiology program office at the Centers for Disease Control and Prevention conducted a study that reviewed 361 research studies on stretching. The results indicated that stretching increased flexibility but this did not decrease injury rates. Injury rates were higher for both the most flexible and least flexible study participants than for those in the mean.6 I have talked with athletes and yoga instructors about overstretching before explosive sports such as soccer and the possibility of too much laxity creating instability and a setup for injury. This would likely hinge on the flexibility of the athlete at baseline. Witvrouw et al believe that part of these contradictions in injury rates of studies can be explained by considering the type of sports activity in which an individual is participating. “Sports involving bouncing and jumping activities with a high intensity of stretch-shortening cycles (SSCs)(e.g. soccer) require a muscle-tendon unit that is compliant enough to store and release the high amount of elastic energy that benefits performance in such sports. If the participants of these sports have an insufficient compliant muscle-tendon unit, the demands in energy absorption and release may rapidly exceed the capacity of the muscle-tendon unit. This may lead to an increased risk for injury of this structure.” They add that recent studies have shown that stretching programs can significantly influence the viscosity of the tendon and make it significantly more compliant for the rigors of high intensity sports.7

How do these findings relate to some of our concepts of treatment? In 2002, Lance Barry, DPM reviewed static gastrocnemius-soleus stretching versus night splints in the treatment of plantar fasciitis. He found that the night splint group had a significantly reduced recovery time. The idea of putting the fascia at physiologic tension versus stretching the gastrocnemius had more of an impact on improving plantar fasciitis. Immobilization, a time honored strategy is part of the treatment with night splints. The splints that extended the toes, in this case the Strausberg Sock, had better results than the other splints although this variable was not part of the study design.8The parallel between these studies is that muscle static stretching just prior to activity does not promote better sports performance and runner's style static standing stretching for plantar fasciitis may damage the fascia and delay healing.

Naturally, there are many variables to consider when determining the best options for athletes and our patients regarding stretching. The evidence leans towards more dynamic stretching as part of a warm up routine in lieu of static stretching immediately prior to activity.

1.Samuel, MN, Holcomb, WR, Guadagnoli, MA, Rubley, MD, and Wallmann, H. Acute effects of static and ballistic stretching on measures of strength and power. J Strength Cond Res 22(5): 1422-1428, 2008
2.Rosenbaum, D. and E. M. Hennig. 1995. The influence of stretching and warm-up exercises on Achilles tendon reflex activity. Journal of Sport Sciences vol. 13, no. 6, pp. 481–90.
3. Fowles, JR DG Sale, JD MacDougall - Journal of Applied Physiology, 2000 - Am Physiological Soc. Vol. 89, Issue 3, 1179-1188, September 2000 Reduced strength after passive stretch of the human plantarflexors
Kokkonen et al. (1998) Research Quarterly for Exercise and Sport
4.Kurz, Tomas, Science of Sports Training, page 236
5.Kokkonen AG Nelson,C Eldredge, JB WInchester - Medicine & Science in Sports & Exercise , 2007 1831. Chronic Static Stretching Improves Exercise Performance.
6.Pope, RP, Herbert, RD, Kirwan JD, Graham, BJ A randomized trial of preexercise stretching for prevention of lower- limb injury. Medicine and Science in Sports and Exercise. 2000; 32:271-277.
7.Witvrouw E, Mahieu N, Danneels L, et al. Stretching and injury prevention: an obscure relationship. Sports Med 2004;34:443-449
8. Barry, Lance D. DPM et al. "A Retrospective Study of Standing Gastrocnemius Soleus Stretching versus Night Splinting in the Treatment of Plantar Fasciitis," The Journal of Foot and Ankle Surgery, Volume 41, Number 4, July/August 2002.