Muscular Force Diagram Problem: – Elbow Flexion
1 Draw the FBD for flexion of the humeroulnar joint.
a. Assume the person is facing the right side of the page and the movement is an angular arc moving to the right of the page.
b. The person is standing and the starting position is 30 degrees from the vertical plane. Assume the upper arm is held straight throughout the ROM.
2 Label all force vectors, angle, and distances.
3 Calculate the force exerted by the biceps brachii muscle on the ulna during 45 degrees of flexion toward horizontal, given the following data and formula:
Distance from humeroulnar joint to biceps brachii insertion 
Radius/ulna centre of mass length 
Distance from humeroulnar joint to wrist 
Mass of radius/ulna 
Mass of weight 
Angle of bicep brachii 
degrees