This is a drawing of a male skeleton, with the muscles overlaid on one side. Study the sizes of the bones in relation to one another, and then notice how the muscles fit over and attach to them. When parts of the skeleton are moved, this has an effect on the shape and form of the muscles relating to that area. This can be seen in the drawing of the arm muscles as the arm bends at the elbow; the bicep contracts and bulges as it pulls the lower arm up, but the tricep located on the back of the arm is stretched and so appears flatter. This is essentially how all the muscles of the body work, they contract or stretch, and as each muscle deforms one way, there is another muscle deforming in opposition to maintain balance and physical stability. It’s an amazing system, well worth taking lots of time to study.
Following in the footsteps of artists who inspire you is a good way to get yourself drawing. It’s how I started out after all! However, sooner or later you will realize that what you’re actually doing is copying their interpretation of how anatomy works without, perhaps, fully understanding it yourself. This is when it’s good to do your own research, essentially building the bones of a deeper knowledge that will improve your work dramatically. I’m not dismissing the notion of learning from your heroes either, as I still do that today, but if you improve your own knowledge, you’ll also be able to glean a little more about the process of how those other artists work.
I’ve also supplied drawings of the leg and back muscles as a purely visual point of reference, so at a glance you can see the different muscle groups, where on the body they attach, and what their relative sizes are. When skin is layered over the top, it will stretch and contort, fold and ripple depending how the muscles beneath are being flexed, stretched, or contracted as the bones move. Bones, muscles, and skin are intrinsically connected, and good figure drawing depends on a solid understanding of how they interact with one another.