Muscles are made up of stands of muscle fiber that contract and release sensory information to the central nervous system. In-between the strands of muscle fiber are muscle spindles that also contract and release sensory information to the central nervous system.
When the deep fiber of the spindle loses the ability to “pick up slack” and contract… the afferents (sensory signals) aren’t released to the central nervous system.
The afferents in the muscle spindle signal the muscle to lengthen… when they’re not released you feel muscle tightness. The muscle loses the end-range of motion… the rotational component. When the muscle contraction is not fully activated to the end range….force potential and proprioception are lost.
Rotation leads to the natural end-range of the hip muscles… allowing the full length of the muscle to fire.
The deeper fiber of the spindle needs a specific treatment to restore the “contract and release” ability of the spindle….a co-contraction. This treatment involves lengthening the muscle to full range using rotation and applying a voluntary isometric force.
The tight muscle is loaded with rotational force and held. After 3 to 10 seconds the rotation is increased until the full rotational length of the muscle is met… approximately 45 degrees.
The combination of length plus rotation creates a co-contraction that reaches the muscle spindle. The muscle spindle is able to release sensory afferents and the muscle is able to contract and lengthen to it’s full length.
When the muscle can contract to the full length you will have a higher recruitment of motor neurons which translates to a stronger contraction. Fully functioning muscle spindles also improve proprioceptive deficiencies since more sensory neurons are releasing information to the central nervous system.