A simplified qualitative method can be used to determine relative
torque forces. As an example we can compare the relative torque
forces through the hip, knee, and ankle joints. First, take a
photograph of barbell squat in a full descent with a perspective
perpendicular to joints plane. Draw a line of force through resistance
on its center of gravity, straight up
and down, parallel to force of gravity. Gravity acting on both
body mass and added mass (barbell) contribute to resistance.
Incidentally, compression forces act upon joints during squat
stance. On the barbell squat, center of gravity is over instep
(between forefoot and heel). If it is not, individual will fall
over, toward the center of gravity.
Now, draw three separate horizontal lines, perpendicular to
line of force from each joint articulation (ankle, knee, and
hip) to line force. If image is not exactly viewed from the side,
"horizontal" lines can be drawn in perspective to picture
as shown. Once diagram is complete, a relative comparison can
be made on the torque forces of the hip, knee, and ankle.