Tiger Athletic Fitness & Conditioning is a private, appointment only strength & conditioning gym in the heart of Sandton offering tailor made, goal-oriented fitness programs. This is the third of three resources, a modest attempt to address some of the frequently asked questions about stretching and flexibility. Here we look at different types of stretching.
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 – Uses, the momentum of a moving body or a limb 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 – Moving parts of your body and gradually increasing reach, speed of movement, or both. Dynamic stretching consists of controlled leg and arm swings that take you to the limits of your range of motion in a controlled fashion. 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 Karate, MMA, Football or Rugby).
Dynamic stretching exercises should be performed in sets of 8-12 repetitions:
Tired muscles are less elastic, which causes a decrease in the amplitude of your movements. Do only the number of repetitions that you can do without decreasing your range of motion. More repetitions will only set the nervous regulation of the muscles’ length at the level of these less than best repetitions and may cause you to lose some of your flexibility. What you repeat more times or with a greater effort will leave a deeper trace in your kinaesthetic memory. After reaching the maximal range of motion in a joint in any direction of movement, you should not do many more repetitions of this movement in a given workout. Even if you can maintain a maximal range of motion over many repetitions, you will set an unnecessarily solid memory of the range of these movements. You will then have to overcome these memories in order to make further progress.
- Active stretching – 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 (or relaxed) stretching – Referred to as relaxed stretching or 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 are an example of a passive stretch in this case the floor is the “apparatus”.
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.
- Static stretching – Many people use the term “passive stretching” and “static stretching” interchangeably. However, there are several people who make a distinction between the two.
Static stretching involves holding a position. That is, you stretch to the farthest point and hold the stretch.
Passive stretching is a technique in which you are relaxed and make no contribution to the range of motion. Instead, an external force is created by an outside agent, either manually or mechanically.
Notice that the definition of passive stretching given in the previous section encompasses both 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 – A type of static stretching 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 provide resistance.
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. Precede 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.
- 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; research has shown that this is not necessary. So, you might as well make your stretching routine less time consuming.
How Isometric Stretching Works
Recall, there is no such thing as a partially contracted muscle fibre: when a muscle is contracted, some of the fibres contract and some remain at rest (more fibres are recruited as the load on the muscle increases). Similarly, when a muscle is stretched, some of the fibres are elongated and some remain at rest. During an isometric contraction, some of the resting fibres are being pulled upon from both ends by the muscles that are contracting. The result is that some of those resting fibres stretch.
Normally, the fibres 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 fibres 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 fibres from contracting.
At this point: When isometrically contracted, some of the resting fibres would contract, many of the resting fibres would stretch, and many of the already stretched fibres, which are being prevented from contracting by the inverse myotatic reflex [the lengthening reaction], would stretch even more. When the isometric contraction was relaxed, and the contracting fibres returned to their resting length, the stretched fibres would retain their ability to stretch beyond their normal limit. I.e. The whole muscle would be able to stretch beyond its initial maximum, and you would have increased flexibility.
The reason that the stretched fibres develop and retain the ability to stretch beyond their normal limit during an isometric stretch has to do with the muscle spindles: The signal which tells the muscle to contract voluntarily, also tells the muscle spindle’s (intrafusal) muscle fibres 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 to an even further-lengthened position.
- Proprioceptive Neuromuscular Facilitation (PNF) – PNF stretching is currently the fastest and most effective way known to increase static-passive flexibility. It is not really a type of stretching but is a technique of combining passive stretching and isometric stretching to achieve maximum static flexibility. 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 like 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) 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 that have managed to achieve a high level of control over their muscle stretch reflex). It is like 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 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 as 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, you probably have no business attempting either of these techniques as the probability of injury is 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 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, 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, to decrease the amount of time taken up by your stretching routine, without decreasing its effectiveness), perform only one PNF technique per muscle group stretched in a given stretching session.
How PNF Stretching Works
During an isometric stretch, when the muscle performing the isometric contraction is relaxed, it retains its ability to stretch beyond its initial maximum length. PNF takes 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:
- 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, serves to fatigue many of the fast-twitch fibres of the contracting muscles. This makes it harder for the fatigued muscle fibres to contract in resistance to a subsequent stretch.
- The tension generated by the contraction activates the Golgi tendon 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 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.
Benefits of Stretching
Stretching can do more than just increase flexibility. Benefits of stretching include:
- Enhanced physical fitness.
- Enhanced ability to learn and perform skilled movements.
- Increased mental and physical relaxation.
- Enhanced development of body awareness.
- Reduced risk of injury to joints, muscles, and tendons.
- Reduced muscular soreness.
- Reduced muscular tension.
- Increased suppleness due to stimulation of the production of chemicals which lubricate connective tissues.
- Reduced severity of painful menstruation (dysmenorrhea) in females.
Unfortunately, even those who stretch do not always stretch properly and hence do not reap some or all these benefits. Some of the most common mistakes made when stretching:
- improper warm-up
- inadequate rest between workouts
- performing the wrong exercises
- performing exercises in the wrong (or sub-optimal) sequence
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- Sport Stretch, by Michael J. Alter.
- Stretching Scientifically, by Tom
- SynerStretch for Total Body Flexibility, from Health for Life.
- The Health for Life Training Advisor, also from Health for Life.
- Mobility Training for the Martial Arts, by Tony Gummerson.
- Bradford D. Appleton.