From what I understand, human arms can be thought of as third class levers, so that the distance from your elbow to the place where the muscle attaches is effectively the distance to the fulcrum, so that arms produce proportionally less strength on the end, and proportionally greater distance when lifting a load. So this is somewhat of an anatomy question (although I suppose if it was to be used for an exoskeleton, it could be robotics) but can leg muscles and the muscles that attach to the ends of arms and legs be roughly modeled in such a way? What muscles/muscle groups don't classify that way?

  • $\begingroup$ Interesting question. I feel like in many cases it would be hard to model the muscles attaching to the hand/foot because of the retinacula in those areas holding them in. I think similar considerations might apply to the muscles moving the fingers/toes. I assume many neck muscles, e.g. sternocleidomastoid might classify in this way, and maybe same for some abdominal muscles. $\endgroup$
    – Anon
    Jan 6, 2017 at 1:46
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    $\begingroup$ Well I can imagine the muscle that attaches from your back to your upper arm (pardon me for not using the anatomical name) as having the fulcrum at the attachment point, and maybe the same with the legs. $\endgroup$
    – Tom
    Jan 6, 2017 at 2:10
  • $\begingroup$ Your question is not that clear - the title asks how to model muscles as levers, while the body seems to focus more on if they can, and if so which ones can and can't. Going by the title, the question is too broad because you don't specify what sort of modeling you'll be doing. Going by the body, it's also too broad, because there are many different types of muscles with different modes of action and varying degrees of fitting into a "lever" model. Please edit your post to focus on a single, clear, answerable question. $\endgroup$
    – MattDMo
    Jan 6, 2017 at 19:19
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    $\begingroup$ AFAIK, you can't model muscles as levers, since they only contract. The bones are the levers. In (physical) model terms, you could think of the skeleton as a bunch of sticks bolted together, with ropes tide to the muscle attachment points. Pull on the rope, and the stick/bone moves. $\endgroup$
    – jamesqf
    Jan 6, 2017 at 19:48


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