When healthy young men perform a specific Tai Chi movement with an elastic band, they generate more force at the elbow and activate more muscle fibers in several arm muscles compared to performing a...
Mechanism
Synthesis from 1 study
Bending the elbow and moving slowly with hands facing forward makes the arm muscles work harder because the position and speed make it harder for the band to slip away, forcing those muscles to push and hold longer. Keeping the shoulders low and hands neutral helps the shoulder muscles stabilize...
Most probable mechanism
When the elbow is held bent and the arms move slowly with the hands facing forward, the muscles that bend the elbow and stabilize the shoulder work harder because the position and speed make it harder for the resistance to slide off, forcing those muscles to push and hold longer. At the same time, keeping the shoulders low and the hands neutral makes the shoulder stabilizers more efficient, while avoiding wide or fast arm movements prevents other muscles from taking over.
The elbow joint is held in a sustained flexed position, increasing the mechanical leverage of resistance forces acting on the joint and requiring greater force production from the biceps brachii, brachialis, and brachioradialis to maintain control.
Slow, uniform movement velocity reduces inertial forces and dynamic loading, prolonging the time under tension for elbow flexors and shoulder stabilizers, which increases neuromuscular recruitment and sustained activation.
Restricted shoulder horizontal abduction and low humeral head position optimize the line of pull for the infraspinatus and coracobrachialis, enhancing their mechanical efficiency in stabilizing the humerus and generating force against resistance.
Neutral hand position alters the direction of resistance relative to the glenohumeral joint, increasing the demand on the infraspinatus and coracobrachialis while reducing the contribution of muscles that act under varus or elevated shoulder positions.
Scapular protraction and internal rotation position the humerus for horizontal adduction, increasing the lever arm and force requirement for the coracobrachialis to control movement against elastic resistance.
Sustained elbow flexion and reduced shoulder abduction torque decrease the mechanical demand on elbow extensors and posterior shoulder muscles, resulting in lower activation of the triceps brachii, posterior deltoid, and subscapularis.
Evidence from Studies
Supporting (1)
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Contradicting (0)
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