Reciprocal inhibition in physiological terms is the contraction of the agonist muscle: describes the process of muscles on one side of a joint relaxing to accommodate contraction on the other side of that joint. Joints are controlled by two opposing sets of muscles, extensors and flexors, which must work in synchrony for smooth movement. When a muscle spindle is stretched and the stretch reflex is activated, the opposing muscle group must be inhibited to prevent it from working against the resulting contraction of the homonymous muscle. This inhibition is accomplished by the actions of an inhibitory interneuron in the spinal cord.
An example is, in the hip flexion the psoas is an agonist, and in the knee extension the agonist is the quadriceps. In its contrast or opposite to the agonists, are antagonistic muscles relax in opposition to the agonist, and that coincidentally are interconnected through nerve innervations, whose function are to allow the muscle activity coordinated by the contraction of some and the relaxation of the other policy makers and stabilize the bones. The antagonists of the psoas and the quadriceps, referring to the previous example, are the gluteus Maximus and the hamstrings respectively.
That seems not seem interesting, even it can be ignored. However, here comes the kit of the issue, the pairs of opposites is one of the great revelations of the scriptures and most ancient sacred philosophies. They state Reciprocal Inhibition is the central point in the sacred texts in the I Ching, the Tao Te King, and the Hindu philosophies. The Hindu one is which reaffirm the compression of the qualities of matter, physical and mental, where you go in future articles.
The concept of stress/strain, contraction/relaxation walks in parallel along with the concepts of yin and yang. Ying and Yang are the representation of the pairs of opposites. In yoga practice is projected toward the biomechanics. The daily practice of yogic discipline, well oriented and guided, allows the practitioner to acquire the ability to gain emotional balance, being level-headed finding the balance between opposites or pairs of opposites.
The reciprocal inhibition is the external, and first step to go ahead and face the importance of working those opposites less perceptible in our ordinary life. Examples, the thermal balance has the perception cold and heat, the emotional states has joy and sadness, success and frustration.
That means, it is going to transform us a better balance way, obviating the polarities and imbalance we suffer.