Stretching

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An actively stretching Siberian tiger

Stretching is a form of physical exercise in which a specific skeletal muscle (or muscle group) is deliberately stretched, often by abduction from the torso, in order to improve the muscle's felt elasticity and reaffirm comfortable muscle tone.^[1] The result is a feeling of increased muscle control, flexibility and range of motion. Stretching is also used therapeutically to alleviate cramps^{[citation needed]}.

In its most basic form, stretching is a natural and instinctive activity; it is performed by humans and many animals. It can be accompanied by yawning. Stretching often occurs instinctively after waking from sleep, after long periods of inactivity, or after exiting confined spaces and areas.

Increasing flexibility through stretching is one of the basic tenets of physical fitness. It is common for athletes to stretch before and after exercise in order to reduce injury^{[citation needed]} and increase performance^{[citation needed]}. Yoga involves the stretching of major muscle groups, some of which require a high level of flexibility to perform, for example the lotus position. Stretching can strengthen muscles, and in turn strong muscles are important to stretching safely and effectively.^{[2][dubious – discuss]}

Stretching can be dangerous when performed incorrectly. There are many techniques for stretching in general, but depending on which muscle group is being stretched, some techniques may be ineffective or detrimental, even to the point of causing permanent damage to the tendons, ligaments and muscle fiber.^[2] The physiological nature of stretching and theories about the effect of various techniques are therefore subject to heavy inquiry.

Physiology

Studies have shed light on a large protein within skeletal muscles named titin. A study performed by Magid and Law demonstrated that the origin of passive muscle tension (which occurs during stretching) is actually within the myofibrils, not extracellularly as had previously been supposed.^[3] Due to neurological safeguards against injury, it is normally impossible for adults to stretch most muscle groups to their fullest length without training due to the activation of muscle antagonists as the muscle reaches its normal range of motion.^[2]

Benefits

A roller derby athlete stretching.

One review suggests that there are many beneficial stretches that can improve range of motion (ROM) in athletes, especially runners.^[4] Another study found that classic "static stretching" did not prevent injuries for runners.^[5]

Also, certain stretching techniques and protocols prevent injuries when performed (within 15 minutes) prior to exercise.^[6]

However, stretching does not prevent delayed onset muscle soreness, neither when performed before nor after exercise, according to a Cochrane review in 2006.^[7]

It is also suggested that one stretching exercise may not be enough to prevent all types of injury, and therefore, multiple stretching exercises should be used to gain the full effects of stretching.^[4]

It has also been suggested that proprioceptive neuromuscular facilitation (PNF) stretching yields the greatest change in range of motion, especially short-term benefits.^[8] Reasoning behind the biomechanical benefit of PNF stretching points to muscular reflex relaxation found in the musculotendinous unit being stretched.^{[clarification needed]} Others^[who?] suggest that PNF benefits are due to influence on the joint where the stretch is felt.^{[clarification needed]}

Research and controversy

A woman in a Yoga stretch position

Over-stretching or stretching to a point where pain is felt may be inappropriate and detrimental. Effects on performance, both short- and long-term, may include predisposition to injury and possible nerve damage.^[4] Other research concludes that active stretching routines will reduce muscle-tendon viscosity and increase muscle compliancy and elasticity. In sports activities where there are little or no short-stretching cycles, (bicycling, jogging, etc.) stretching routines may be detrimental to athletic performance and have no effect on reducing injuries.^[9]

Stretching may also cause ischemia in muscles,^{[citation needed]} which reduces oxygen levels and the ability to remove metabolic waste. Higher levels of metabolic waste create a catalyst that contracts muscles. This may cause muscle injury in individual performance. Other theories included claim active static stretching increases inflow of Ca²⁺ from extra cellular spaces into the muscles being stretched. The increase of Ca²⁺ reduced the muscle twitch tension by up to sixty percent. Reasoning behind this claim is that increased levels of Ca²⁺ in resting muscles predisposes individuals to fatigue quicker than individuals who did not stretch.^[10]

Flexibility

Some people are more flexible than others as defined by individual body flexibility score; this includes sex differences where females are generally more flexible than males.^{[citation needed]} Stretching may not increase range of motion,^{[citation needed]} but rather increase individual stretch tolerance, becoming detrimental to athletic performance.^{[citation needed]} Among the factors these studies measure are capsular mobility, FlexiScore and joint-muscle compliance.

Results of research by Witrouw et al.^[9] found that: each of which has a different consideration based on individual activity:

• In activities where stretch-shortening cycles (SSC) are more prevalent, such as sprinting and jumping, the muscle-tendon units need to store and use more elastic energy
• In activities which do not require as much SSC such as jogging, a more elastic muscle-tendon unit is not needed.^{[clarification needed]}

The reason behind conflicting data is claimed to be due to the different levels of observed sports activity.

Footnotes

Further reading

• Andersen, J. C. "Stretching Before and After Exercise: Effect on Muscle Soreness and Injury Risk". Journal of Athletic Training 40(2005): 218–220.
• Cheung, Karoline, Patria A. Hume, and Linda Maxwell. "Delayed Onset Muscle Soreness: Treatment Strategies and Performance Factors". Sports Medicine 33.2(2003): 145–164.
• LaRoche, Dain, and Declan A. J. Connolly. "Effects of Stretching on Passive Muscle Tension and Response to Eccentric Exercise". American Journal of Sports Medicine 34.6(2006): 1000–1007.
• Shrier, Ian. "When and Whom to Stretch?" Physician & Sportsmedicine 33.3(2005): 22–26.

External links

Wikimedia Commons has media related to: Stretching

• CMcrossroads.com, Stretching and Flexibility
• MayoClinic.com, Mayo Clinic Stretching info
• Stretching.name, Stretching routines
• Fitness-central.co.uk, Types of Stretching
• Amateurendurance.com, Daily Stretch Routine