POST 46: STATIC AND DYNAMIC STRETCHING

This post highlights the differences between stretch types.

The different types of stretching are:
  1. ballistic stretching
  2. dynamic stretching
  3. active-static stretching
  4. passive-static (or relaxed) stretching
  5. isometric stretching
  6. PNF stretching

1. Ballistic Stretching

Ballistic stretching was the preferred stretch type when I began dancing (long time ago…aged 5). I ballistic stretches I would bounce in the stretch position. For example: I would hang forward with my legs in second and bounce to reach the floor. Since, I reached the floor I was told to fold my arms and aim to ‘get elbows to the floor’. This stretch type will not be used in my proposal as all research links this to injury. Injury results as the momentum of the bounce attempts to force movement at the joint beyond the normal range of motion. Muscles have no time to adjust or relax in the stretched position. Literature suggests that the muscles tighten up by repeatedly activating the stretch reflex.

2.  Dynamic stretching

Dynamic stretching involves movement at a joint and gradually increasing speed, extension or both. The temperature generated is beneficial to muscle movement due to enzyme activation and coordination of the nerve impulses (Powers & Hawley, 2007) and activation of contractile elements which increase force-velocity and length-tension of muscles (Bishop, 2003). Dynamic stretch does not involve movement passed the range of motion. Dynamic stretching has been linked with increases in power. Research work by McNair (2000)[1] and Knudson (2001)[2] suggests that dynamic stretches  are the most appropriate exercises for the warm-up with 8-10 repetitions.

I regularly perform dynamic stretches at the start of my classes. I encourage  8 repetitions of plies, side lunges, kicks and arm swings. I notice as students tire their muscles loose elasticity and range of movement. I encourage complete movements but I am careful do not overwork students as  this could cause the nervous system to regulate muscle length at less than that achieved during initial repetitions and consequently reduce flexibility.

To continually improve dancers they must overcome the muscle memory (nervous conduction) at their current range of motion. This can be encouraged by initially reducing the replication number.

3. Active-static stretching

Active stretching uses the strength of an active antagonistic muscle to maintain the maxim extended position of a relaxed stretched muscle.

My references show static stretching increases active flexibility of the stretched muscle and strengthens antagonistic muscles. I include yoga based static stretches within the cool down of my classes.  My use of active stretches has been augmented by my attendance in yoga classes which improve my understanding of the use of breath and alignment in maintaining static stretches.

Students find difficulty relaxing the stretched muscle as they lack strength needed to maintain tension in the agonist muscle for more than 10 seconds. The weaker this reciprocal inhibition the more tension retained in the relaxed muscle and the less extension possible.  Research shows prolonged static stretching reduces the power and strength in muscles reducing the benefit to dance. It is my role as a teacher to end the active stretch at an appropriate time.

4. Relaxed/Passive-static stretching

In passive stretch the position is held by another body part, apparatus or with a partner. The complexity in teaching static stretches results from the need to relax the muscles and release into the stretch without adding to the range of motion. Working in pairs requires students to trust their partner and to maximise their practice by learning from others. Students enjoy working to gently increase the extended position of partners. Slow, relaxed stretching is useful in relieving spasms in muscles that are healing after an injury. Research shows that passive stretching is suited to cooling down and has ben linked to reduction in post-workout muscle fatigue, and soreness.

5. isometric (somatic) stretching

Isometric stretching is a sub-type of static stretching which involves the resistance of muscle groups through isometric contractions (tensing) of the stretched muscles in a particular position. Resistance is provided by the dancer, a partner or apparatus e.g. wall.

Research suggests somatic stretching increases static-passive flexibility more effectivey 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.

I work with students individually to correct position for passive stretch of the desired muscle. They tense the stretched muscle for 7-15 seconds by pushing against a fixed surface. The muscle is then relaxed for at least 20 seconds. Students also work in pairs to provide resistance. For example holding the leg whilst the dancer pushes it to the floor. Research suggests that dynamic stretches should be performed  to warm stretched muscle before isomeric stretches. Isometric stretching places excessive demands on muscles and should not be performed more than once a day.

Isometric stretching will not be used in my proposal as is not recommended for children and adolescents whose bones are still growing. Young 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 tissues.

5. Isometric stretching

When a muscle is stretched, some of fibers are elongate and some remain a rest. Isometric contractions develop the existing stretch by some of the resting fibers being pulled upon from both ends by the muscles that are contracting. This results in the stretching of some resting fibers. If contraction is held the initial passive stretch overcomes the stretch reflex, enabling more fibres to activate This triggering of the inverse myotatic reflex [the lengthening reaction], overcomes the inhibition which would otherwise prevent stretched fibers contracting. This results as the neuronal signal activating voluntarily muscle contraction also tells 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 become accustomed to an even further-lengthened position.

It would be worth considering the effect of isometric stretching in my proposal

6. PNF stretching

Research promotes proprioceptive neuromuscular facilitation (PNF) stretching as the most effective protocol to increase static-passive flexibility.  The technique of PNF achieves maximum static flexibility by combining passive stretching  and isometric stretching.

Although originally developed to benefit rehabilitation of stroke victims, PNF stretching has now evolved to include several post-isometric relaxation stretching techniques.

The theory is that 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 is most effective if a partner provides resistance against the isometric contraction and then passively takes the joint through its increased range of motion. It may be performed with less effect without a partner.

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.

How PNF Stretching Works

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:

  1. 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.
  2. 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).
  3. 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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