When healthy young men perform a Tai Chi movement with an elastic band, their shoulder joints move more slowly and steadily than when they perform a reverse fly motion with the same band.
Mechanism
Synthesis from 1 study
When you move your arms slowly with bent elbows and low shoulders, your muscles don’t have to fight sudden jerks or heavy pulls. This lets them work steadily, keeping the motion smooth and even, without speeding up or slowing down unexpectedly.
Most probable mechanism
When the shoulder moves slowly and smoothly with limited range, the forces acting on the joint stay steady, so muscles don't need to suddenly speed up or slow down. This lets certain muscles work more steadily to hold the arm in place, while others don't have to fight against sudden jerks or heavy pulls. The way the arm is positioned — with the elbow bent and the shoulder low — makes it easier for some muscles to do their job without needing to generate big bursts of force, which keeps the motion smooth and even.
Shoulder horizontal abduction is performed within a restricted angular range, reducing the mechanical demand for rapid acceleration and deceleration of the humerus.
Slow and uniform angular velocity minimizes inertial forces and dynamic loads on the glenohumeral joint, decreasing the need for compensatory muscle bursts to control momentum.
Sustained elbow flexion alters the line of pull of the resistance band, increasing torque demand on elbow flexors while reducing demand on elbow extensors, promoting stable, low-velocity movement.
Low shoulder elevation and neutral hand position enhance mechanical efficiency of the infraspinatus and coracobrachialis, allowing them to stabilize the humeral head and control adduction with sustained, low-intensity force.
Scapular protraction and internal rotation position the humerus to favor continuous horizontal adduction, requiring prolonged activation of coracobrachialis without high-velocity contractions.
Reduced torque demand on shoulder abductors and external rotators decreases recruitment of posterior deltoid and subscapularis, eliminating high-force, high-velocity muscle contributions that drive variability.
Lower neuromuscular activation of triceps brachii and other extensors prevents eccentric braking and explosive extension, further stabilizing movement velocity.
Evidence from Studies
Supporting (1)
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Contradicting (0)
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