Stabilizer muscle

A stabilizer muscle holds a bone steady or limits movement at a joint so motion can occur elsewhere.^{1International Sports Sciences Association, Bodybuilding: The Complete Guide to Unlocking Muscle Hypertrophy, 1st ed., p. 34.},^{2International Sports Sciences Association, Fast Track Study Guide: Applied Science, p. 29.} During a leg lift, the rectus abdominis contracts isometrically to stop the pelvis tilting forward.^{1International Sports Sciences Association, Bodybuilding: The Complete Guide to Unlocking Muscle Hypertrophy, 1st ed., p. 34.}

ISSA distinguishes static stabilizers, which hold a joint still with an isometric contraction, from dynamic stabilizers, which work concentrically or eccentrically while the joint moves.^{3International Sports Sciences Association, Corrective Exercise, 1st ed., p. 149.} The rotator cuff illustrates dynamic stabilization: during an overhead press, it restricts excess shoulder motion through the concentric and eccentric phases.^{3International Sports Sciences Association, Corrective Exercise, 1st ed., p. 149.}

In practice

Even a one-arm dumbbell curl needs wrist muscles to hold the wrist neutral, shoulder muscles to stabilize the joint, and neck, back and core muscles to stabilize the spine.^{4International Sports Sciences Association, Strength and Conditioning, p. 43.}

Trunk strength transfers force between the feet and hands.^{5International Sports Sciences Association, Corrective Exercise, 1st ed., p. 146.} In a standing overhead press, weakness in the trunk lets it bend or buckle as force passes through it.^{5International Sports Sciences Association, Corrective Exercise, 1st ed., p. 146.} A heavy dumbbell held at one side pulls the trunk toward lateral flexion, requiring the opposite side’s muscles to hold posture.^{5International Sports Sciences Association, Corrective Exercise, 1st ed., p. 146.}

ISSA’s corrective exercise text argues that some tight muscles don’t need stretching; activating underactive stabilizers can instead improve mobility at the neighboring joint.^{6International Sports Sciences Association, Corrective Exercise, 1st ed., p. 194.}