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.
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 perform by an individual when a partner is unavailable (eg: modified versions of the standing single leg hamstring stretch and standing quadriceps stretch).