In an extensive
comprehensive review of international research papers concerning
indications and effectiveness of different stretching techniques, there
appears to be no agreement. There seem to exist a vast amount of
stretching techniques, each with its own described precise application.
However, the theoretical models attached to these stretching techniques
are based on incomplete scientific study or basis.
Most studies show
that each individual technique seems to have some value when the goal is
to improve mobility. The majority of the studies identify the short-term
effects of stretches on the subjects, but none deal with the long-term
conclude that the application of their technique improve mobility which is
dependent on properties of the connective tissue rather than on
studies were done and compared results of static, post-isometric and
dynamic stretching of the hamstrings. All three stretching methods showed
an increase in hamstrings mobility.
method was superior to the static model; however, the largest increment of
mobility was gained by the dynamic stretch technique.
tried to identify what factors resulted in the improvements of mobility.
Findings showed that improvement is based on an increased tolerance of the
muscle-tendon unit to stretch triggers. Stretching did not change the
probably caused a mechanical elongation to bring about an effective
lengthening of connective tissue; however, this was only maintained over a
short period of time.
Another aspect of
stretching was reviewed in regards to whether it improved muscle
regeneration. Three different stretching techniques were studies which
were static stretch, intermittent dynamic stretch and post-isometric
The findings showed
that static stretching consistently resulted in worsening of muscle
regeneration. The post-isometric relaxation had an inconsistent influence,
where in some subjects it led to improvement, in others worsening of
intermittent dynamic stretching led to an overall improvement in muscle
regeneration. One researcher commented that static stretching may actually
slow the regeneration process as it may compress the capillary system and
interrupt vascularization. Good vascularization is needed to flush out the
metabolic intermediate and end products of forceful muscle activity.
Many therapists who
do not have access to objective measuring methods rely on Sherrington
Principle of Reciprocal Inhibition to explain their stretching techniques.
However, researchers using EMG measuring methods have not observed this
reciprocal inhibition. The question arises whether the basic models for
neurophysiological reflexes really exist.
have remarked that the role of the connective tissue as the most important
factor in resistive stretching is overestimated. At the same time, the
researchers feel that the resistance of muscles to stretch in
underestimated. Muscle imbalances of agonist and antagonist can be
explained by Sherrington’s Law of Reciprocal Innervation.
This law implies
that a strained or tight muscle will inhibit its antagonist. Therefore,
the tight muscles will create weak antagonistic muscles which create a
muscle imbalance that adversely affects the normal pattern of muscle
movement. Strengthening these tight muscles will have the effect of
further increasing the tightness and perpetuating the antagonistic
concept should be applied that before strengthening exercises are
prescribed, muscle tension must be released through stretching prior to
any strengthening. Strengthening already tight muscles will promote
further weakness and imbalances.
flexibility of both the agonist and antagonist will allow for a more
balanced strengthening and elimination of one muscle group dominance.
facilitation or PNF is a technique commonly associated with contract-relax
stretching (hold-relax) and contract-relax agonist contraction methods. At
present, researchers have not found evidence for a mechanism behind the
effectiveness of PNF techniques.
techniques use volitional contractions in an attempt to achieve increased
range of motion by minimizing the active component of resistance
attributed to spinal reflex of pathways.
In the hold-relaxed
agonist contraction method, the contraction and relaxation of the muscle
to be stretched (antagonist) is followed by a concentric contraction of
the muscle opposing the muscle to be stretched (agonist) to inhibit
further the antagonist through the alpha-gamma co-activation and
techniques have been based on neurophysiological factors resulting in
neuroinhibition of the muscle undergoing stretch, researchers have now
disproved that. Researchers point that it is the mechanical factors rather
than the stretch factors that are responsible for the increased length and
stretching after PNF.
response is based on the muscle-tendon unit responding to its
viceroelastic properties allowing for length increases without stretching.
The elastic component related to stretch are directly related to the
applied force while the viscus properties are time dependent and late
change dependent, such that the rate of deformation is directly
proportional to the applied forces.
Studies have also
looked at whether slow repetitive speeds or high explosive speeds improve
muscle strength and endurance. Although slow repetitive speeds have
a definite place in the development in hypertrophy and focal muscle
endurance, they have minimal improvement in developing absolute or speed
High threshold motor
neurons are optimally recruited at high tension, and this requires
acceleration. As a rule of thumb, lower the weight over two to three
second duration and then launch the weight with as much explosive power as
possible to improve muscle building and strength.
The slow twitch
fibers respond to higher weights and slower speeds whereas the fast twitch
fibers respond more quickly with greater gains with acceleration and lower
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Copyright © 2004 - 2012Taras V.
Kochno, M.D. All Rights Reserved
Board Certified in
Physical Medicine and Rehabilitation