Human movement is dependent on the amount of range of motion (ROM) available in synovial joints. In general, ROM may be limited by 2 anatomical entities: joints and muscles. Joint restraints include joint geometry and congruency as well as the capsuloligamentous structures that surround the joint. Muscle provides both passive and active tension: passive muscle tension is dependent on structural properties of the muscle and surrounding fascia, while dynamic muscle contraction provides active tension. Structurally, muscle has viscoelastic properties that provide passive tension. Active tension results from the neuroreflexive properties of muscle, specifically peripheral motor neuron innervation (alpha motor neuron) and reflexive activation (gamma motor neuron).

Factors contributing to muscle tension.

Obviously, there are many factors and reasons for reduced joint ROM only one of which is muscular tightness. Muscle “tightness” results from an increase in tension from active or passive mechanisms. Passively, muscles can become shortened through postural adaptation or scarring; actively, muscles can become shorter due to spasm or contraction. Regardless of the cause, tightness limits range of motion and may create a muscle imbalance.