The maintenance of a full, non-restricted range of motion has long been recognized as critical to injury prevention and as an essential component of a conditioning program.
The goal of any effective flexibility program should be to improve the range of motion at a given articulation by altering the extensibility of the musculotendinous units that produce movement at that joint. It is well documented that exercises that stretch these musculotendinous units over a period of time increase the range of movement possible about a given joint.
Stretching techniques for improving flexibility have evolved over the years. The oldest technique for stretching is called ballistic stretching, which makes use of repetitive bouncing motions. A second technique, known as static stretching, involves stretching a muscle to the point of discomfort and then holding it at the point for an extended time, this technique has been used for many years. Recently another group of stretching techniques known collectively as proprioceptive neuromuscular facilitation (PNF), involving alternating contractions and stretches, has been recommended.
Before discussing the three different stretching techniques it is essential to define the terms agonist and antagonist muscles. Most joints in the body are capable of more than one movement. The knee joint, for example, is capable of flexion and extension. Contraction of the quadriceps group of muscles on the front of the thigh causes knee extension, whereas contraction of the hamstring muscles on the back of the thigh produces knee flexion.
To achieve knee extension, the quadriceps group contracts while the hamstring muscles relax and stretch. The muscle that contracts to produce a movement, in this case the quadriceps, is referred to as the agonist muscle. The muscle being stretched in response to contraction of the agonist muscle is called the antagonist muscle. In knee extension, the antagonist muscle would be the hamstring group. Some degree of balance in strength between agonist and antagonist muscle groups is necessary for normal smooth coordinated movement and for reducing the likelihood of muscle strain caused by muscular imbalance.
