a standard man intending to do reverse curls in a gym. He holds his arms straight, using an overhand grip to hold the bar. If the mass of the bar is given as 140 kg, what is the tension in each of his shoulders? Consider the weight of the arm and the weight of the bar. Note: Use 4.9kg as the mass of the arm of the standard man.

Question

MathMate · Answer

I don't do reverse curls, and am not too sure what it is. This is what I learned:
http://www.exrx.net/WeightExercises/Brachioradialis/BBReverseCurl.html

I suppose the best approximation is to assume that the two shoulders assume the total weight of the bar and the arms (4.9 kg includes the wrist and the fingers, hopefully).

So load each shoulder would shoulder
(140+4.9+4.9)/2=74.9 kg = 734 N

However, since it is a tension on the arm, I am not too sure if it would be a tension on the shoulder. The calculation of the muscle/tendon forces are rather complex without a good knowledge of human anatomy.