Commentary on the stretching debate

Introduction:

An article by Rod Herbert and Michael Gabriel, published in the British Medical Journal in August 2002, triggered a worldwide controversy on the use of stretching in sports medicine as well as for lay people. Reviewing several studies their article came to the conclusion “Stretching before and after exercise does not confer protection from muscle soreness. Stretching before exercise does not seem to confer a practically useful reduction in the risk of injury …”

The following is part of “The stretching debate”, published in the April 2003 issue of Journal of Bodywork and Movement Therapies.

Commentary, byRobert Schleip
Critical questioning by scientists about common stretching assumptions is not new. German research in the mid 90ies already showed that most of the common hypotheses about the neurophysiological effects in stretching are wrong (Wiemann & Hahn 1997, Freiwald 1998). E.g. it had been postulated that brief active contraction prior to stretching would lead to a following tonus decrease in the stretched muscle. Similarly it had been suggested that a simultaneous antagonist contraction during static stretching would achieve the same. Yet the German measurements have shown that both procedures actually lead to an increased excitability of the musculature as well as a slightly increased muscle resistance to stretching. It had also been assumed that a slow and long stretch at a moderate force would lead to a tonus decrease, yet these EMG measurements have shown that there is generally a slow tonus increase when a joint is moved close to its maximum range of motion. Given the complex properties of biological soft tissues these findings, as well as those of Herbert & Gabriel should not be too surprising. Nevertheless it is plausible that prolonged static stretching directly after exercise might be contraindicated for regeneration, as static stretching is likely to inhibit capillary blood supply in the stretched tissues (similar to the water extrusion in squeezing a sponge).

It is important to remember that stretching is practiced for many different reasons. Herbert & Gabriel only looked at three possible intentions: injury prevention in sports, prevention of muscle soreness, and an increase of sports performance in athletes. But stretching is also used to increase range of motion in the case of chronic myofascial shortness due to muscular imbalance, post trauma or post surgery. One recent study found that cyclic stretching stimulates the secretion of growth factors of tendon fibroblasts and may have a positive influence on tendon and ligament healing through stimulation of cell proliferation, differentiation and matrix formation (Skutek 2001). Further research is needed to clarify what type of stretching over which time frame is advisable for which conditions. There is evidence that active dynamic stretching techniques seem to be more effective for increasing range of motion than static stretching (Wiemann & Hahn 1997). A muscle is strongest at about its midrange of potential length. In many people certain muscle groups are dominantly used in shortened positions due to repetitive movement (in sports or at a work station), poor posture, or a sedentary life style. In these cases the tissue may slowly adapt by reducing its ultimate fiber length so that the habitually used joint position becomes the new 'middle position' where the muscle can work most economically. One approach that may gradually lead to a lengthening process is to give the tissue regular stimulations when it is both actively used and in extended positions.

This has an interesting parallel in the field of myofascial tissue manipulation, where the practitioner may attempt to loosen soft tissue restrictions by stretching the tissues using the application of manual pressure. It had been assumed by several authors that this type of passive stretching would stimulate the Golgi-tendon organs, which would then induce a tonus decrease of the shortened muscle fibers. Yet more detailed studies have revealed that these stretch receptors are generally not stimulated by passive stretching. This research supports the use of myofascial release techniques in which the patient temporarily contracts the same tissues which are being worked on. It seems that in both areas, stretching and tissue manipulation, there is a trend towards more active movement participation, and that this shift is a reflection of recent research findings.

Regarding the benefits of stretching for athletes, it is advisable to differentiate between activities in which a wide range of free joint motion is important (in this case regular stretching may be beneficial) and activities in which explosive contraction power is more essential. E.g. for free style long distance swimmers a wide and free arm swing is necessary. On the other hand it was already shown in the German studies of the mid 90ies that static stretching immediately prior to vertical jumping tends to have a negative effect on the jumping height (Hennig & Podzielny 1994).

Comparing the differences in joint utilization between humans and other primates, Australian researchers found that we humans are less prone to develop rheumatic osteoarthritis in those joints (like the elbow) which we tend to use in a similar wide range of motion as our primate friends. Whereas joints which we generally use in a more limited range of motion (like the cervical spine, shoulder, hand, fingers, knee and hip joint) are more likely to develop this degeneration (Alexander 1994). Regular dynamic stretching and other forms of gymnastics might therefore prove to be good prevention against rheumatic arthritis and possibly other joint diseases.

 

Other possible advantages of stretching may include psychological functions. E.g. before sports brief static stretching may be good for the overly nervous or hyper agitated athlete, and active dynamic stretching may be better for persons who would profit from some general activation. So far there is also no research on the possible effects of stretching on proprioception. Since clinical studies have shown strong correlations between dysfunctions like chronic low back pain (Radebold 2001) or idiopathic scoliosis (Keesen 1992) with a reduced proprioceptive accuracy, this field of research may offer valuable inspiration. It seems that there are many interesting interrelations between body image organization, chronic pain, post traumatic stress disorders, psychological and physical aging, and proprioceptive accuracy. Static stretching like as is often performed in conventional Hatha yoga, as well as various forms of dynamic stretching could indeed prove to have profound effects in this important dimension.

Conclusion: More research is needed to determine which type of stretching has what kind of advantages and side effects for what type of condition. Herbert and Gabriel’s research for athletes (and the unprecedented international attention given to their publication) make a valuable contribution in this direction.

References:

    • Alexander CI 1994 Utilization of joint movement range in arboreal primates compared with human subjects: an evolutionary frame for primary osteoarthritis. Annals of Rheumatic Diseases 53(11):720-725
    • Freiwald J et al. 1998 Stretching--do current explanatory models suffice? Sportverletzung Sportschaden, 12(2):54-59
    • Hennig E, Podzielny S 1994 Die Auswirkungen von Dehn- und Aufwärmübungen auf die Vertikalsprungleistung. Deutsche Zeitschrift für Sportmedizin 45:253-260
    • Keesen W et al. 1992 Proprioception in idiopathic scoliosis. Spine 17(2):149-155
    • Radebold A et al. 2001 Impaired postural control of the lumbar spine is associated with delayed muscle response times in patients with chronic idiopathic low back pain. Spine, 26(7):724-730
    • Skutek M et al. 2001 Cyclic mechanical stretching modulates secretion pattern of growth factors in human tendon fibroblasts. European Journal of Applied Physiology 86:48-52
  • Wiemann K, Hahn K 1997 Influences of strength, stretching and circulatory exercises on flexibility parameters of the human hamstrings, International Journal of Sports Medicine 18:340-346

 

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