Improving flexibility through stretching is another important preparatory activity that has been advocated to improve physical performance. Maintaining good flexibility also aids in the prevention of injuries to the musculoskeletal system. Flexibility is defined as the range of motion possible around a specific joint or a series of articulations and is usually classified as either static or dynamic. Static flexibility refers to the degree to which a joint can be passively moved to the end-points in the range of motion. Dynamic flexibility refers to the degree which a joint can be moved as a result of a muscle contraction and may therefore not be a good indicator of stiffness or looseness of a joint.
There are 3 basic categories of stretching techniques: (a) ballistic — which makes use of repetitive bouncing movements; (b) static — which stretches the muscle to the point of slight muscle discomfort and is held for an extended period; and (c) proprioceptive neuromuscular facilitation — which uses alternating contractions and stretching of the muscles. Each of these stretching methods is based on the neurophysiological phenomenon involving the stretch reflex. The muscle spindle and Golgi tendon organ are receptors sensitive to changes in muscle length and tension and are activated during stretching. Because ballistic, static, and proprioceptive neuromuscular facilitation stretching techniques produce different responses from the stretch reflex, the relative effectiveness of these stretching methods also varies.
Studies comparing the effectiveness of the various stretching techniques have been confusing and contradictory. However, the majority of the information on this topic tends to support the use of proprioceptive neuromuscular facilitation techniques for providing the best improvements in flexibility.