Reciprocal Inhibition

RECIPROCAL INHIBITION

eciprocal inhibition

n : a method of behavior therapy based on the inhibition of one

response by the occurrence of another response that is

mutually incompatible with it; a relaxation response

might be conditioned to a stimulus that previously evoked

anxiety [syn: reciprocal-inhibition therapy]

Reciprocal Inhibition

• The Lengthening Reaction: (previous subsection)

• What Happens When You Stretch: (beginning of section)

When an agonist contracts, in order to cause the desired motion, it usually forces the antagonists to relax (see section Cooperating Muscle Groups). This phenomenon is called reciprocal inhibition because the antagonists are inhibited from contracting. This is sometimes called reciprocal innervation but that term is really a misnomer since it is the agonists which inhibit (relax) the antagonists. The antagonists do not actually innervate (cause the contraction of) the agonists.

Such inhibition of the antagonistic muscles is not necessarily required. In fact, co-contraction can occur. When you perform a sit-up, one would normally assume that the stomach muscles inhibit the contraction of the muscles in the lumbar, or lower, region of the back. In this particular instance however, the back muscles (spinal erectors) also contract. This is one reason why sit-ups are good for strengthening the back as well as the stomach.

When stretching, it is easier to stretch a muscle that is relaxed than to stretch a muscle that is contracting. By taking advantage of the situations when reciprocal inhibition does occur, you can get a more effective stretch by inducing the antagonists to relax during the stretch due to the contraction of the agonists. You also want to relax any muscles used as synergists by the muscle you are trying to stretch. For example, when you stretch your calf, you want to contract the shin muscles (the antagonists of the calf) by flexing your foot. However, the hamstrings use the calf as a synergist so you want to also relax the hamstrings by contracting the quadricep (i.e., keeping your leg straight).

Reciprocal inhibition

This describes muscles on one side of a joint relaxing to accommodate contraction on the other side of that joint.

The body handles this pretty well during activities like running, where muscles that oppose each other are engaged and disengaged sequentially to produce coordinated movement. This facilitates ease of movement and is a safeguard against injury. Sometimes, for example, a football running back can experience a "misfiring" of motor units and end up simultaneously contracting the quads and hamstrings during a hard sprint. If these muscles, which act opposite to each other are fired at the same time, at a high intensity, a tear can result. The stronger muscle, usually the quadriceps