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, by Robert 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:
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Back to the article collection
This commentary is part of the article The stretching debate': Commentaries
by: J. Beam, J. DeLany, W. Haynes, R. Lardner, C. Liebenson, S. Martin, P.
Rowland, R. Schleip, J. Sharkey, B. Vaughn Response by: R. Herbert and M.
Gabriel,