fantastic!

Thanks! I was pretty happy with it too, though I sort of got the proportions a bit wrong and didn't end up with space for head or feet.

haha that's okay, as long as you're getting the basic idea =) you can improve on proportions as you go along. gotta start somewhere and this kind of thing doesn't just happen overnight.

Erk. Muscles. But good pic xD

Thanks!
We are all made of muscles...

hmm,
it's a decent attempt,the sternocletomastoid is placed awkwardly but you've got the right idea the trapezius are attached in the right place, but remember the muscle is in use since the arm is lifting, so instead of relaxed it should be tense and thick. i love how you took the time to see how the pectorals work by being attached to the humerus and not the ribcage (error made by millions) and adding the latissimus and the teres major under the pectorals, the serratus are present but the ones on the right are a bit anomalous to define their location now the top row of the abs are somewhat still attached with the serratus across the body.
on the arms, on the one that's lifted the coracobrachialis is missing and by the height and angle the arm is in, there should be little to no visibility of the deltoid on the top. now on the coccyx you might've gotten it right but remember theres a ligament that makes the inguilan line with narrows down the abdomen
the right arm just loses information quickly as i head in the mid section of the bicep and below, theres no brachialis no brachioradiais, no pronator teres, basically none of the flexor and extensor muscles it just becomes into a garbled mess.

now on the thighs, there is some readability in the muscles, enough for me to recognize, the vastus medialis and lateralis are present, wrongly, but there, good job adding the sartorius and what seems to be the tensor fascia latae, though on the left life it should have a tiny sliver of the gluteus medusa peeking out on the side, the adductors are visible but awkwardly placed, it should be placed into the pectineal line, (pubis) all those adductor muscles group in that particular place.

lower than that it just becomes unreadable

my advice for you is to study the skeleton, you have a basic grasp on anatomy, but you need to know the landmarks and laces were certain muscles attaches to

I was just drawing what I was seeing in a diagram. I don't actually know much at all about the muscles and where they attach.

"I was just drawing what I was seeing in a diagram"
u sure?, or did you guess the rest?'
"I don't actually know much at all about the muscles and where they attach."
haha that's why i gave this critique and and suggested that it's beneficial to learn this.

Well to truly draw exactly what you see is quite a difficult task. I try to draw what I see, but I don't always get every tiny detail perfect.

it's not difficult, it's just time consuming, people tend to dissmiss things because there's too much information/detailing in things, so they skip it and try to formulate their own way to bs the whole thing, i'm rootin 4 u tho haha