Incorrect moment diagram in squat article?

[me80iq]

No, it's not...we are concerned with the Forces / Torque / Moments present during an instant in time, which is what the diagram is illustrating.

Kinematics: the branch of mechanics concerned with the motion of objects without reference to the forces which cause the motion.

Statics: the branch of mechanics that is concerned with the analysis of loads (force and torque, or "moment") acting on physical systems that do not experience an acceleration (a=0), but rather, are in static equilibrium with their environment.

Dynamics: the branch of mechanics concerned with the study of forces and their effects on motion. (a does not = 0)

You might find this hard to believe, but a number of us SSCs have backgrounds in Engineering or Physics. This material has been scrubbed, discussed, argued over, etc.

Yeah you're right I mistyped. I meant this isn't statics, it includes kinematics. Which is what separates dynamics and statics.

I do believe that some SSCs have backgrounds in engineering or physics. I also have a bachelor's in mechanical engineering. Doesn't mean much. People still makes mistakes all the time. As I have done here :^).

[AndrewLewis]

So, for the edification of the layman (such as myself)... the descriptor provided in the diagram is statics. What would it be if you calculated the moment, leverage, torque and compression on each joint for a period or instance of the movement?

Look up "free body diagram."

Basically, you make a figurative 'cut' at the location you are interested in and balances the forces and moments assuming a net force and net moment of 0. From there, you have to use the area of the cross section to calculate the stress (compression/tension) on the component at that's specific location.

[David A. Rowe]

Who cares, David? The diagram is designed to show you that moment force is calculated from the gravity vector, that there are 2 points of rotation on either end of the thigh and the shank, and that there are therefore 2 moment arms on each of these segments, the lengths of which can be manipulated by your position/technique to variously affect the muscle groups that operate the moment arms. Does it do that? I didn't write an engineering book because I'm not that smart. I was trying to illustrate a concept. Did I succeed?

Well, I cared in the context of picking up pieces of information that help me frame things better. I've learned very late in life that I'm dyslexic, so it helps me to put those things in their categories, visualize it and move one. I have been on the forums in various capacities for a while now, and I've had a few encounters with you, coaches and staff where my question was either stupid, seemed tedious or pet the cat the wrong direction because it seemed to be coming from the same sort of individual who asks incredible shallow and repetitive things.

Believe me... I get your frustration. I deal with it personally and professional, too. Please take me at face value when I say the information and material produced by you and others has helped me tremendously, and that I'm not trying to critique or condescend. I'm just trying to clarify, and it's because I'm trying to learn. Because I'm not well informed, either, when it comes to engineering, but I do find it fascinating.

[Mark Rippetoe]

You're fine, David.