Do most voluntary human movement involve the rotation of a body part around an imaginary axis of rotation that passes through the center of a joint?

Yes, the most voluntary human movement involve the rotation of a body part around an imaginary axis of rotation that passes through the center of a joint.

Explanation:

The "Center of Gravity" is an point around which body weight is 'evenly distributed'. The gravity center of the body of a human can change to a considerable extent because the 'segments of the body' can drift their 'masses' with joint rotations.The force of gravity in the body is in downward direction, towards the center of the earth The "line of gravity" is very significant for "determining a person's ability" to maintain balance. A reaction is needed when this 'center of gravity' falls outside the base.