(RI) Reciprocal Inhibition – describes the process where the muscles of one side of a joint relax in order to accommodate a greater contraction in the muscles on the other side of the joint.
Without RI muscles on both sides of a joint may fire simultaneously and work against each other.
RI is typically used to achieve greater range of motion in a stretch. You may have heard of “Contract/Relax” – yea thats RI and the Golgi Tendon Organs at work.
How it occurs doesn’t really matter to you.
What does matter is what you do after.
The only reason to stretch a muscle is to promote length and greater range of motion. Once that extra range is created you must then train it!
Mobility is Posture Specific: I would not suggest stretching any muscle in isolation – but to do mobility exercises that relate directly to a functional movement (like a squat).
This way you point all your arrows in the right direction.
This process takes advantage of the stretch reflex and is an effect way of literally training your reflexes. Something you will want to have later in life.