Posted by **jim** on Sunday, December 5, 2010 at 8:45pm.

A weightlifter performing a curl with a 320 N barbell stops the lifting motion with his forearms

in a horizontal position. (a) If the line of action of the weight of the barbell is 27 cm from the

axis of rotation (elbow joint), what is the magnitude of the moment that the elbow flexors must

exert to maintain that position? (b) If the weight of the weightlifter’s forearms and hands were

taken into account, would the moment that the elbow flexors had to exert be more or less than

that calculated in part (a)? If the biceps were the only elbow flexor muscle active (a rather

unlikely event) and its moment arm about the elbow joint was 4.3 cm, calculate the biceps

muscle force needed to maintain this equilibrium position.

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