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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 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 (see section 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).
See section Warming Up.
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 (see section
Cooperating Muscle Groups). 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 (see section 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 (see section
Pain and Discomfort).
Relaxed stretching is also very good for "cooling down" after a workout and helps
reduce post-workout muscle fatigue, and soreness. See section
Cooling Down.
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 (see section
Types of Muscle Contractions). 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 provide resistance.
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 (see section
How Muscles Contract) 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 (see section
What Happens When You Stretch). 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 (see section The Stretch Reflex)
and triggers the lengthening reaction (see section
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 muscle
spindles (see section Proprioceptors): 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 position.
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 PNF technique.
- 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 technique.
- 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 (see section
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
section 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 section 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 things:
- 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 (see section Fast and Slow Muscle Fibers).
This makes it harder for the fatigued muscle fibers to contract in resistance
to a subsequent stretch (see section The Stretch
Reflex).
- The tension generated by the contraction activates the golgi tendon organ
(see section Proprioceptors), which inhibits
contraction of the muscle via the lengthening reaction (see section
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.
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by Brad Appleton
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