Squat Physics

[Goat97]

Hi! 

My friends and I were having a heated debate yesterday. The question was whether when one squats is the downward force exerted on the legs (hips to feet) the same if the shoulders and arms help support the bar OR if the arms are just there to hold the bar in place? The arms holding the bar do not move they are just flexed and holding the bar off the shoulders. The distance the bar has to go down is equal to the distance the legs are going down in both problems.

If there are any variables that i could have forgotten to say please add them,  thanks!

 

[swansont]

Your legs are supporting all the weight carried by your upper body, regardless of whether your arms are exerting themselves or not; the downward force is the same.

What does not account for, is the fact that you are not a rigid body. You may have to exert yourself more to stay balanced if you are e.g. holding the weight over your head. These are forces exerted perpendicular to the vertical.

[J.C.MacSwell]

Assuming the weight and body move in the same manner the force on the legs is the same. If the speed of the movement varied the forces would vary as well. 

[Bender]

Since your arms are springs, the force on your legs could be lower when you start going down, but higher when you near the lowest point.

[mistermack]

If the bar rests on the shoulders, none of it's weight is transferred through the arm joint. You could theoretically take your hands off the bar. 

If you hold the bar off your shoulders, all of the weight is routed through the muscles and joint of the arms. 

In both cases, the same identical weight is routed down through the spinal column to the legs and feet. It's just routed differently at shoulder level.