This article is from the Stretching FAQ, by Brad Appleton Brad_Appleton@ivhs.mot.com with numerous contributions by others.
PNF stretching is currently the fastest and most effective way known to
increase static-passive flexibility. PNF is an acronym for "proprioceptive
neuromuscular facilitation". It is not really a type of stretching but is
a technique of combining passive stretching (See "3.4 - Passive
Stretching") and isometric stretching (See "3.6 - Isometric Stretching") in
order to achieve maximum static flexibility. Actually, the term PNF
stretching is itself a misnomer. PNF was initially developed as a method
of rehabilitating stroke victims. PNF refers to any of several
"post-isometric relaxation" stretching techniques in which a muscle group
is passively stretched, then contracts isometrically against resistance
while in the stretched position, and then is passively stretched again
through the resulting increased range of motion. PNF stretching usually
employs the use of a partner to provide resistance against the isometric
contraction and then later to passively take the joint through its
increased range of motion. It may be performed, however, without a
partner, although it is usually more effective with a partner's assistance.
Most PNF stretching techniques employ "isometric agonist
contraction/relaxation" where the stretched muscles are contracted
isometrically and then relaxed. Some PNF techniques also employ "isometric
antagonist contraction" where the antagonists of the stretched muscles are
contracted. In all cases, it is important to note that the stretched muscle
should be rested (and relaxed) for at least 20 seconds before performing
another PNF technique. The most common PNF stretching techniques are:
This technique is also called the "contract-relax". After assuming an
initial passive stretch, the muscle being stretched is isometrically
contracted for 7-15 seconds, after which the muscle is briefly relaxed
for 2-3 seconds, and then immediately subjected to a passive stretch
which stretches the muscle even further than the initial passive
stretch. This final passive stretch is held for 10-15 seconds. The
muscle is then relaxed for 20 seconds before performing another PNF
This technique is also called the "contract-relax-contract", and the
"contract-relax-antagonist-contract" (or "CRAC"). It involves
performing two isometric contractions: first of the agonists, then, of
the antagonists. The first part is similar to the hold-relax where,
after assuming an initial passive stretch, the stretched muscle is
isometrically contracted for 7-15 seconds. Then the muscle is relaxed
while its antagonist immediately performs an isometric contraction that
is held for 7-15 seconds. The muscles are then relaxed for 20 seconds
before performing another PNF technique.
This technique (and a similar technique called the "hold-relax-bounce")
actually involves the use of dynamic or ballistic stretches in
conjunction with static and isometric stretches. It is *very* risky,
and is successfully used only by the most advanced of athletes and
dancers that have managed to achieve a high level of control over
their muscle stretch reflex (See "1.6.2 - The Stretch Reflex"). It is
similar to the hold-relax technique except that a dynamic or ballistic
stretch is employed in place of the final passive stretch.
Notice that in the hold-relax-contract, there is no final passive stretch.
It is replaced by the antagonist-contraction which, via reciprocal
inhibition (See "1.6.4 - Reciprocal Inhibition"), serves to relax and
further stretch the muscle that was subjected to the initial passive
stretch. Because there is no final passive stretch, this PNF technique is
considered one of the safest PNF techniques to perform (it is less likely
to result in torn muscle tissue). Some people like to make the technique
even more intense by adding the final passive stretch after the second
isometric contraction. Although this can result in greater flexibility
gains, it also increases the likelihood of injury.
Even more risky are dynamic and ballistic PNF stretching techniques like
the hold-relax-swing, and the hold-relax-bounce. If you are not a
professional athlete or dancer, you probably have no business attempting
either of these techniques (the likelihood of injury is just too great).
Even professionals should not attempt these techniques without the guidance
of a professional coach or training advisor. These two techniques have the
greatest potential for rapid flexibility gains, but only when performed by
people who have a sufficiently high level of control of the stretch reflex
in the muscles that are being stretched.
Like isometric stretching (See "3.6 - Isometric Stretching"), PNF
stretching is also not recommended for children and people whose bones are
still growing (for the same reasons. Also like isometric stretching, PNF
stretching helps strengthen the muscles that are contracted and therefore
is good for increasing active flexibility as well as passive flexibility.
Furthermore, as with isometric stretching, PNF stretching is very strenuous
and should be performed for a given muscle group no more than once per day
(ideally, no more than once per 36 hour period).
The initial recommended procedure for PNF stretching is to perform the
desired PNF technique 3-5 times for a given muscle group (resting 20
seconds between each repetition). However, `HFLTA' cites a 1987 study
whose results suggest that performing 3-5 repetitions of a PNF technique
for a given muscle group is not necessarily any more effective than
performing the technique only once. As a result, in order to decrease the
amount of time taken up by your stretching routine (without decreasing its
effectiveness), `HFLTA' recommends performing only one PNF technique per
muscle group stretched in a given stretching session.