Stretching

Stretching is extending the limbs, lengthening and relaxing muscles, and moving joints through their range of motion to maintain and improve muscle and joint flexibility. Stretching has an important role in fitness as well as in everyday functioning.

Stretching can improve flexibility, ease movement, and relieve muscle tension. It may increase blood flow to muscles; improve posture, balance, coordination, strength, and physical performance; reduce fatigue; and help prevent overuse injuries. Stretching can help joints move through their full range of motion, improving biomechanics and athletic performance. Regular stretching may lengthen muscle fibers so that they contract more vigorously during exercise. Stretching also can relax muscles and may help prevent soreness or stiffness: tight muscles reduce the body's range of motion and joint fluidity and can impair balance and contribute to back pain or difficulty performing simple tasks. Some researchers believe that muscle cramps may be caused by inadequate stretching that leads to abnormalities in the control of muscle contraction.

For many people, stretching is an enjoyable activity that can be performed anywhere at any time. It can be a pleasant way to begin and conclude a workout. Stretching also can relax muscles that are contracted due to emotional tension and stress, especially back and neck muscles. Chronically tensed muscles are a risk factor for pain and injury. Gentle stretching also is relaxing for the mind.

Stretching is usually directed at major muscle groups, including the calves, thighs (hamstrings and quadriceps), hip flexors, chest, back (lower, middle, and upper), arms (biceps, triceps, and forearms), shoulders (deltoids and rotator cuffs), and neck, as well as other muscles and joints that are used regularly. The stretched muscle should be positioned such that there is a slight pull but no pain. Stretching should always be balanced, with the right and left sides stretched for the same amount of time. The American College of Sport Medicine recommends stretching activities at least two days per week, or daily for people with stiff muscles or loss of joint motion.

Stretches can be particularly beneficial if they are sport- or activity-specific, focusing on the muscles used in the activity. For example, soccer players are more at risk for hamstring sprains, so stretching should focus on the hamstrings, the muscles of the back of the thigh. Baseball players might focus on shoulder stretches for throwing or forearm stretches for batting. Activity-specific movements, such as a front kick in martial arts, can be performed slowly, at low intensity, and gradually speeded up over the course of the warm-up.

Dynamic stretches can help prepare the body for an active workout or competition. They are slow, controlled movements that take the muscles and joints through their full range of motion. Dynamic stretching can be as simple as arm circles, hip rotations, walking or jogging exercises, or yoga movements. Many other types of dynamic stretching can be done.

There are many sport-specific dynamic stretches. Runners often perform squats, lunges, and buttock kicks. Sports that require moving rapidly in different directions, such as soccer, tennis, and basketball, utilize dynamic stretches, such as the spiderman, which is crawling on the hands and feet as if climbing a wall.

Total-body static stretches should be performed slowly and gently for four to six minutes after a workout or competition to lengthen muscles and increase flexibility. Deep, relaxed breathing helps prevent muscle tension. There should be a slight pull or tightness on the muscle that is sustained for 10–60 seconds, without bouncing, and repeated three to five times. Areas to stretch include:

Proprioceptive neuromuscular facilitation (PNF) was developed in the 1940s and 1950s as physical therapy for paralysis. During the 1980s, sports therapists and trainers adapted some of its techniques for increasing range of motion. PNF stretching combines passive and active stretches. Both isometric muscle contraction (“hold”) and concentric muscle contraction (“contract”), followed immediately by a passive stretch, facilitate a reflex relaxation called autogenic inhibition. Reciprocal inhibition is a reflex relaxation or stretching the muscle opposing the muscle that is stimulated. Rope stretching is similar to PNF but with a rope instead of a partner.

Three PNF stretches for the hamstrings illustrate these principles. Each stretch begins by lying on the back with one leg on the floor and the other extended straight up. A partner moves the extended leg to the point of mild discomfort and holds it in a passive stretch for 10 seconds before one of the following stretches:

Like PNF, active isolated stretching (AIS) is based on the theory that working one muscle group, such as the biceps, relaxes and lengthens the opposing muscle group, in this case the triceps. Each active stretch lasts only a few seconds and is repeated about 10 times. Although special stretching ropes are available, a jump rope or dog leash can be used.

Proper stretching technique is extremely important. Incorrect stretching is not only ineffective, it may cause injury. Muscles must be warmed up before stretching because stretching cold muscles can directly contribute to pulled or torn muscles. Movements must always be carefully controlled. Stretching should never be painful, forced, or move a joint beyond its normal range. Slow, easy stretching is particularly important for older inactive adults who lack muscle elasticity. The benefits are lost if stretching is not performed on a regular basis.

Experts generally advise that static stretching should only be performed following exercise because it elicits a neuromuscular inhibitory response that can last up to 30 minutes and decrease muscle strength by as much as 30%. In contrast, dynamic stretches can be performed before a workout because they do not illicit an inhibitory reaction, although they should not cause preworkout fatigue. A 2016 analysis of more than 200 studies on the effects of stretching reported that the inhibitory effects of static stretching are brief and generally occur only if each stretch is held more than 50 seconds and is followed immediately by full activity with no further warm-up. Furthermore, the authors reported that at least five minutes of short static stretches during a warm-up significantly reduced the risk of straining or tearing a muscle.

Static stretching should always be sustained rather than ballistic (with bouncing or bobbing). Bouncing can cause small muscle tears that leave scar tissue, further tightening muscles, decreasing flexibility, and potentially causing pain. Holding most stretches for less than 10–30 seconds will not sufficiently lengthen the muscle. Some proponents of active stretching, such as PNF or AIS, argue that static stretching cuts off blood flow to muscle and provokes a protective reflex. Stretching does not speed the removal of waste products from muscles, as is sometimes claimed.

Some traditional stretches, such as the hurdler's stretch and the yoga plow, are now considered illadvised because they put excessive pressure on the knees and back, respectively. Other stretches should not be performed by people with certain medical conditions. For example, knee-to-chest stretches should not be performed by anyone with osteoporosis because it can increase the risk of compression fractures of the vertebrae.

PNF stretching is not recommended for anyone under age 18. Only one PNF exercise should be performed on a muscle group in a single session, and exercisers should wait at least 48 hours between sessions. PNF stretching should not be performed on the day of a competition.

Although stretching is safe if performed correctly, it can cause further injury, for example, to an already strained muscle. People with injuries or chronic medical conditions should consult their physician or physical therapist about stretching techniques or adaptations.

As of 2016, the benefits and potential risks of various forms of stretching, as well the best timing for stretching, were areas of intensive research. Static stretching, in particular, remains controversial. One study of a static reach-and-hold hamstring stretch found that performing it daily for four weeks increased hamstring flexibility by about 20 degrees; continuing to stretch two or three days a week for another four weeks added another four degrees, but not continuing led to a loss of seven degrees of flexibility. Other studies, however, have found no benefit from static stretching. Although dynamic stretching before a workout is generally believed to increase power, flexibility, and range of motion, it is unclear if it helps prevent injury.

See also Exercise ; Fatigue ; Warm-up and cool-down ; Yoga .