Flexibility is the range of motion possible around a specific joint or series of articulations. Flexibility is specific to a given joint or movement. A person may not be able to function normally if a joint lacks normal movement. The ability to move a joint through an adequate range of movement is important for daily activities in general as well a sports performance. For example, a sprinter may be handicapped by tight, inelastic hamstring muscles since the ability to flex the hip joint will be limited, thus shortening stride length. Activities such as gymnastics, ballet, diving, karate, and yoga require improved flexibility or even the ability to hyperextend some joints for superior performance.
On the other hand, most leisure or recreational activities require only normal amounts of flexibility. The idea that good flexibility is essential for successful performance is based on anecdotal rather than scientific evidence.
Adequate range of movement may be more important for long term injury prevention. Individuals involved with physical activity who have poor flexibility (specific or general) risks exceeding the extensibility limits of the musculoskeletal unit. Once flexibility is assessed and flexibility insufficiency are identified, a stretching program can be customized, emphasizing those areas in need of improvement. See flexibility assessments and Joint Ranges of Motion.
Four basic types of stretch techniques include ballistic, dynamic, static, and proprioceptive neuromuscular facilitation (PNF).
The oldest technique is the ballistic stretch which makes use of repetitive bouncing movements. It has been virtually abandoned by almost all experts in the field due to safety concerns.
Dynamic stretching incorporates movements that mimic a specific sport or exercise in an exaggerated yet controlled manner; often include during the warm-up or in preparation for a sports event.
The static technique involves passively stretching a muscle to the point of mild discomfort by holding it in a maximal stretch for an extended period. It remains a very effective, relatively safe, and popular method of stretching. Recommendations for the optimal holding time are varied, ranging from 10 seconds to 60 seconds. See stretches in the Exercise Directory.
PNF (proprioceptive neuromuscular facilitation) techniques involve a partner actively stretching the participant by some combination of altering contraction and relaxation of both agonist and antagonist muscles. Some of the different PNF techniques used include slow reversal hold, contract relax, and hold relax. PNF stretching usually involves a 10 second push phase followed by a 10 second relaxation phase, typically repeated a few times. PNF stretching is capable of producing greater improvement in flexibility compared to other techniques. Its disadvantage is that, it typically requires a partner, although stretching with a partner may have some motivational advantage for some individuals. Examples include:
Ninos J (2001) has proposed particular PNF stretches that can be performed by an individual when a partner is unavailable (eg: modified versions of the standing single leg hamstring stretch and standing quadriceps stretch).
Contrary to popular belief, stretching before a workout does not appear to decrease the occurrence of injury. The risk of injury seems to be about equal to those who stretch and those who do not stretch before exercise. The warm-up, not stretching, seems to be the important deterrent for injury, performed before an exercise bout. Stretching seems to offer more long term benefit such as maintaining functional flexibility and correcting particular muscular imbalances.
Shrier's (1999) review of the literature found three articles that suggested stretching was beneficial included a co-intervention of warm-up. One study found stretching was associated with less groin/buttock problems in cyclists, but only in women. Five studies suggesting no difference in injury rates between stretchers and non-stretchers and three suggesting stretching was detrimental. One reason stretching is thought to be ineffective in reducing the risk of injury is the fact that most muscle injuries occur when the muscle is eccentrically contracted within the normal range of motion (Shrier 1999). It seems more flexible individuals do not necessarily have less incidence of injury (Gleim 1997). In some cases, those with greater flexibility may actually experience more injury, particularly if the excessive flexibility compromises joint integrity (Surberg 1983; Jones 1997). Although excessive flexibility may contribute to joint laxity, flexibility and joint integrity are not necessarily mutually exclusive. It may be possible for a joint to possess a combination of exceptional flexibility and excellent joint integrity.
Greater flexibility may impair performance in sports that do not require a high degree of flexibility such as running. Runners with less flexibility are actually more efficient at running (Jones 2002). Intense static stretching may also reduce maximum force production. The loss of voluntary strength and muscular power may last up to one hour after the static stretch (Evetovich 2003, Young 2003). People who participate in activities that require more than average flexibility (eg: gymnasts, dancers, figure skaters) may still find stretching beneficial to their performance.
The ACSM recommends flexibility training a minimum 2 to 3 days per week holding each stretch for 10 to 30 seconds to mild discomfort; 3 to 4 repetitions per stretch. On PNF stretches, ACSM suggests a contract 6 seconds followed by a 10 to 30 second assisted stretch.
McCallister et. al. (2004) found that longer recovery days between stretching seemed to enhance stand and reach measurements:
|Rest (hours)||Stand & Reach (cm)|
This data suggests it may not be necessary to stretch daily, but instead take a few days recovery between sessions.
Weight training and stretching exercises have been considered complimentary. Resistance training can increase the stiffness of the tendon structures as well as strengthen the muscles, whereas static stretching changes the viscosity of tendon structures, but not its elasticity (Kubo et. al 2002).
Many full range weight training exercises could be considered a kind of dynamic stretch under a load. These types of weight training exercises can improve and maintain a degree of flexibility depending on their movement, range of motion in which they are performed, and existing levels of flexibility.
Although stretching does not seem to offer many short term benefits when performed before exercise, stretching does seem to offer other long term benefits. Improved flexibility may help alleviate and help prevent back and other orthopedic problems. Individuals with certain muscular imbalances or postural problems can benefit from stretching. Stretching can help maintain flexibility which may otherwise decline with age or inactivity due to an injury. Stretching may be more safely performed after dynamic exercise, when muscles are warm. Unless an activity requires extreme flexibility, stretching before is probably unnecessary. And even then, stretches should be performed after a warmup.
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