During a forceful tennis serve, why does the elbow joint experience significantly higher shear stress compared to the shoulder joint, given both contribute to the kinetic chain?

💡 Explanation

The elbow joint experiences higher shear stress due to the shorter moment arm relative to the muscles acting across the elbow. This reduced lever arm requires greater force at the joint to generate the same torque, because force is inversely proportional to the moment arm in torque calculations; therefore, shear stress increases. Rather than inherently weaker ligaments or greater muscle force at the elbow, the biomechanics of the lever system dictate the stress distribution.

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