I notice that most anatomy books don't show you how the whole muscle looks by itself, only how they look all bundled together. And they also tend to show muscles colored in red, which makes it a little harder to discern them individually.
These Halloween skeletons are not truly anatomically correct, usually. They are fairly simplified. But their proportions are more or less close enough. I'm primarily interested in the superficial muscles, as they apply to drawing, so I'll be simplifying it too.
Step 1: Materials
bake and bend sculpey mixed into muted colors $7-$8
optional: pin vise, small drill bit and large jump rings for jointing the arms.
You could try this with Sugru if you're fast enough. Though I worried that the 30 minute working time just wasn't enough. Note: Sugru does seem to bond to these plastic skeletons reasonably well.
Step 2: Muscles of the upper leg
Step 3: Muscles of the lower leg
I know I'm oversimplifying the lower leg (and lower arm)...
Step 4: Muscles of the torso and upper arm
Step 5: Muscles of the back and upper arm
supraspinatus, infrapinatus, teres minor
Step 6: Muscles of the lower arm
(I'm a little fuzzy on these lower arm muscles, they may be a bit mixed up)
flexor carpi radialis
I know I'm skipping a huge number of muscles in the lower arms. its very complicated.
Step 7: Neck muscles
there are others, but this skeleton is too tiny to do the neck muscles!
Step 8: Muscular fellows showing off their physiques
I don't dare bake the sculpey because I'm pretty sure these plastic skeletons couldn't withstand the heat. Maybe I'll try again using sugru to make it more permanent.
I didn't do the hands, feet or facial muscles because the skeletons are just too small. Maybe in another instructable.