Muscle energy is defined by the Education Council on Osteopathic Principles (ECOP) as “a form of osteopathic manipulative diagnosis and direct treatment in which the patient’s muscles are actively used on request, from a precisely controlled position, in a specific direction, and against a distinctly executed counterforce.”

Muscle energy is a direct and active technique, meaning it engages a restrictive barrier and requires the patient’s participation in relieving the somatic dysfunction. The goal of muscle energy is to reduce pain and help normalize range of motion within a restricted joint or muscle by relieving tension within the surrounding muscle groups.

There are two types of muscle energy: post-isometric relaxation and reciprocal inhibition. 

For post-isometric relaxation, the patient is instructed to move away from the restrictive barrier, whereas for reciprocal inhibition, the patient is instructed to move toward the restrictive barrier. Post-isometric relaxation is much more commonly used.

Muscle energy achieves pain relief and muscle relaxation by utilizing specialized structures in the muscles called Golgi tendon organs and muscle spindles. The Golgi tendon organ is a proprioceptor that senses how much tension a muscle is exerting. The muscle spindle is a mechanoreceptor that senses changes in muscle length. Together, these units help manage muscle control and coordination.

When the Golgi tendon organ senses increased tension within a muscle belly, it responds by inhibiting the contraction of the respective (agonist) muscle group while activating contraction of the opposing (antagonist) group. A muscle spindle within the muscle belly is activated when it senses an increase in length, resulting in contraction of the agonist muscle and relaxation of the antagonist muscle.

Post-isometric relaxation takes advantage of the physiology pertaining to Golgi tendon organs, resulting in relaxation of hypertonic musculature. Reciprocal inhibition, on the other hand, takes advantage of the biomechanics behind muscle spindles and prevents overstretching of muscles via activation of the antagonist muscle.