The following is an article on stretching collected from usenetgroups.
Just as there are different types of flexibility, there are also different types of stretching. Stretches are either dynamic (meaning they involve motion) or static (meaning they involve no motion). Dynamic stretches affect dynamic flexibility and static stretches affect static flexibility (and dynamic flexibility to some degree).
The different types of stretching are:
- ballistic stretching
- dynamic stretching
- active stretching
- passive (or relaxed) stretching
- static stretching
- isometric stretching
- PNF stretching
Ballistic stretching uses the momentum of a moving body or a limb in an attempt to force it beyond its normal range of motion. This is stretching, or "warming up", by bouncing into (or out of) a stretched position, using the stretched muscles as a spring which pulls you out of the stretched position. (e.g. bouncing down repeatedly to touch your toes.) This type of stretching is not considered useful and can lead to injury. It does not allow your muscles to adjust to, and relax in, the stretched position. It may instead cause them to tighten up by repeatedly activating the stretch reflex.
Dynamic stretching, according to Kurz, "involves moving parts of your body and gradually increasing reach, speed of movement, or both." Do not confuse dynamic stretching with ballistic stretching! Dynamic stretching consists of controlled leg and arm swings that take you (gently!) 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 are no bounces or "jerky" movements. An example of dynamic stretching would be slow, controlled leg swings, arm swings, or torso twists.
Dynamic stretching improves dynamic flexibility and is quite useful as part of your warm-up for an active or aerobic workout (such as a dance or martial-arts class).
According to Kurz, dynamic stretching exercises should be performed in sets of 8-12 repetitions. Be sure to stop when and if you feel tired. Tired muscles have less elasticity which decreases the range of motion used in your movements. Continuing to exercise when you are tired serves only to reset the nervous control of your muscle length at the reduced range of motion used in the exercise (and will cause a loss of flexibility). Once you attain a maximal range of motion for a joint in any direction you should stop doing that movement during that workout. Tired and overworked muscles won't attain a full range of motion and the muscle's kinesthetic memory will remember the repeated shorted range of motion, which you will then have to overcome before you can make further progress.
Active stretching is also referred to as static-active stretching. An active stretch is one where you assume a position and then hold it there with no assistance other than using the strength of your agonist muscles. For example, bringing your leg up high and then holding it there without anything (other than your leg muscles themselves) to keep the leg in that extended position. The tension of the agonists in an active stretch helps to relax the muscles being stretched (the antagonists) by reciprocal inhibition .
Active stretching increases active flexibility and strengthens the agonistic muscles. Active stretches are usually quite difficult to hold and maintain for more than 10 seconds and rarely need to be held any longer than 15 seconds.
Many of the movements (or stretches) found in various forms of yoga are active stretches.
Passive stretching is also referred to as relaxed stretching, and as static-passive stretching. A passive stretch is one where you assume a position and hold it with some other part of your body, or with the assistance of a partner or some other apparatus. For example, bringing your leg up high and then holding it there with your hand. The splits is an example of a passive stretch (in this case the floor is the "apparatus" that you use to maintain your extended position).
Slow, relaxed stretching is useful in relieving spasms in muscles that are healing after an injury. Obviously, you should check with your doctor first to see if it is okay to attempt to stretch the injured muscles.
Relaxed stretching is also very good for "cooling down" after a workout and helps reduce post-workout muscle fatigue, and soreness.
Many people use the term "passive stretching" and "static stretching" interchangeably. However, there are a number of people who make a distinction between the two. According to M. Alter, Static stretching consists of stretching a muscle (or group of muscles) to its farthest point and then maintaining or holding that position, whereas Passive stretching consists of a relaxed person who is relaxed (passive) while some external force (either a person or an apparatus) brings the joint through its range of motion.
Notice that the definition of passive stretching given in the previous section encompasses both of the above definitions. Throughout this document, when the term static stretching or passive stretching is used, its intended meaning is the definition of passive stretching as described in the previous section. You should be aware of these alternative meanings, however, when looking at other references on stretching.
Isometric stretching is a type of static stretching (meaning it
does not use motion) which involves the resistance of muscle groups through
isometric contractions (tensing) of the stretched muscles. The use of isometric stretching is one of the
fastest ways to develop increased static-passive flexibility and is much more
effective than either passive stretching or active stretching alone. Isometric
stretches also help to develop strength in the "tensed" muscles (which helps to
develop static-active flexibility), and seems to decrease the amount of pain
usually associated with stretching.
The most common ways to provide the needed resistance for an isometric
stretch are to apply resistance manually to one's own limbs, to have a partner
apply the resistance, or to use an apparatus such as a wall (or the floor) to
An example of manual resistance would be holding onto the ball of your foot
to keep it from flexing while you are using the muscles of your calf to try and
straighten your instep so that the toes are pointed.
An example of using a partner to provide resistance would be having a partner
hold your leg up high (and keep it there) while you attempt to force your leg
back down to the ground.
An example of using the wall to provide resistance would be the well known
"push-the-wall" calf-stretch where you are actively attempting to move the wall
(even though you know you can't).
Isometric stretching is not recommended for children and adolescents
whose bones are still growing. These people are usually already flexible enough
that the strong stretches produced by the isometric contraction have a much
higher risk of damaging tendons and connective tissue. Kurz strongly
recommends preceding any isometric stretch of a muscle with dynamic strength
training for the muscle to be stretched. A full session of isometric stretching
makes a lot of demands on the muscles being stretched and should not be
performed more than once per day for a given group of muscles (ideally, no more
than once every 36 hours).
The proper way to perform an isometric stretch is as follows:
- Assume the position of a passive stretch for the desired muscle.
- Next, tense the stretched muscle for 7-15 seconds (resisting against some
force that will not move, like the floor or a partner).
- Finally, relax the muscle for at least 20 seconds.
Some people seem to recommend holding the isometric contraction for longer
than 15 seconds, but according to SynerStretch (the videotape),
research has shown that this is not necessary. So you might as well make your
stretching routine less time consuming.
Recall from our previous discussion that there is no such thing as a partially contracted
muscle fiber: when a muscle is contracted, some of the fibers contract and some
remain at rest (more fibers are recruited as the load on the muscle increases).
Similarly, when a muscle is stretched, some of the fibers are elongated and some
remain at rest. During an isometric contraction, some of the
resting fibers are being pulled upon from both ends by the muscles that are
contracting. The result is that some of those resting fibers stretch!
Normally, the handful of fibers that stretch during an isometric contraction
are not very significant. The true effectiveness of the isometric contraction
occurs when a muscle that is already in a stretched position is subjected to an
isometric contraction. In this case, some of the muscle fibers are already
stretched before the contraction, and, if held long enough, the initial passive
stretch overcomes the stretch reflex and triggers the lengthening reaction, inhibiting the stretched fibers from contracting. At
this point, according to SynerStretch, when you isometrically
contracted, some resting fibers would contract and some resting fibers would
stretch. Furthermore, many of the fibers already stretching may be prevented
from contracting by the inverse myotatic reflex (the lengthening reaction) and
would stretch even more. When the isometric contraction is completed, the
contracting fibers return to their resting length but the stretched fibers would
remember their stretched length and (for a period of time) retain the ability to
elongate past their previous limit. This enables the entire muscle to stretch
beyonds its initial maximum and results in increased flexibility.
The reason that the stretched fibers develop and retain the ability to
stretch beyond their normal limit during an isometric stretch has to do with the
The signal which tells the muscle to contract voluntarily, also tells the muscle
spindle's (intrafusal) muscle fibers to shorten, increasing sensitivity of the
stretch reflex. This mechanism normally maintains the sensitivity of the muscle
spindle as the muscle shortens during contraction. This allows the muscle
spindles to habituate (become accustomed) to an even further-lengthened
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 section Passive Stretching) and isometric stretching (see section 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:
- the hold-relax
- 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
- the hold-relax-contract
- 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
- the hold-relax-swing
- 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. It is similar to the hold-relax technique except that a
dynamic or ballistic stretch is employed in place of the final passive
Notice that in the hold-relax-contract, there is no final passive stretch. It
is replaced by the antagonist-contraction which, via 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
Like 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.
Remember that during an
isometric stretch, when the muscle performing the isometric contraction is
relaxed, it retains its ability to stretch beyond its initial maximum length
(see section How Isometric Stretching Works). Well, PNF tries to take immediate advantage of
this increased range of motion by immediately subjecting the contracted muscle
to a passive stretch.
The isometric contraction of the stretched muscle accomplishes several
- As explained previously (see section How Isometric Stretching Works), it helps to train the stretch receptors of
the muscle spindle to immediately accommodate a greater muscle length.
- The intense muscle contraction, and the fact that it is maintained for a
period of time, serves to fatigue many of the fast-twitch fibers of the
contracting muscles. This makes it harder for the fatigued muscle
fibers to contract in resistance to a subsequent stretch.
- The tension generated by the contraction activates the golgi tendon organ,
which inhibits contraction of the muscle via the lengthening reaction. Voluntary contraction during a stretch increases
tension on the muscle, activating the golgi tendon organs more than the
stretch alone. So, when the voluntary contraction is stopped, the muscle is
even more inhibited from contracting against a subsequent stretch.
PNF stretching techniques take advantage of the sudden "vulnerability" of the
muscle and its increased range of motion by using the period of time immediately
following the isometric contraction to train the stretch receptors to get used
to this new, increased, range of muscle length. This is what the final passive
(or in some cases, dynamic) stretch accomplishes.