Flexibility has long been recognized as a key factor for maximizing exercise and preventing injuries. Of course, the best way to gain flexibility is through stretching. As a result of increased flexibility, less stress is placed on joints, muscles, and connective tissues (ligaments and tendons).

Muscles contain receptors, known as proprioceptors, that relay muscle activity information to the central nervous system (CNS). When a muscle reaches a point of maximum stretch, these proprioceptors signal the CNS to cause a reflex contraction of the muscle (Fig.1). After a period of a few seconds, another set of proprioceptors signal a reflex relaxation of the muscle. This is the body's method of preventing overstraining and tearing of the muscle fibers.

Certain stretching techniques, such as ballistic and static stretching, use the reflex contractions and relaxations signaled by the proprioceptors in an attempt to increase an athlete's flexibility. Ballistic stretching involves the use of quick, bouncing movements and is not routinely recommended due to the risk of muscle strains (Fig. 1). Static stretching requires the muscle to slowly be placed into a position of stretch and then held at that point (Fig. 2).

Recently, a third flexibility technique called Proprioceptive Neuromuscular Facilitation (PNF) has grown popular. PNF allows the muscle to be stretched to a greater degree by increasing the proprioceptor signals through a 5- to 10-second voluntary muscle contraction followed by a 5- to 10-second voluntary muscle relaxation. With the hold-relax PNF method, the muscle is placed into a static stretch. The athlete is instructed to "hold" and contract the muscle against resistance from a partner for 10 seconds (Fig. 3). The athlete is then instructed to "relax," and the partner slowly moves the muscle to a new static position. The technique is repeated two to three times.

Just as with any stretching activity, PNF should be performed after a proper warm up, using correct body mechanics and motion that is pain free.

David Yeager, ATC, CCS
Columbus, Georgia