I figured asking you would be the best source. How did you learn and study anatomy? I'm having trouble with proportions and muscle movement. Got any tips? Thanks for taking the time to read this!
I learned by making a whole lot of mistakes! That, and taking a vested interest in developing my skills in my free time.
Through personal experience, learning both proportion and muscle movement is best tackled through learning about the skeleton. Studying the skeleton puts into perspective the origins of the various masses of the body - what they do, why they are there, what gives them their form. It will also introduce you to how the body moves. Understanding how the skeleton works will give you a very important groundwork for how the muscles in the body interact, and how and why they deform when in motion.
Speaking strictly on proportions of the human body, it is in your best interest to familiarise yourself with the concept of “7 ½ heads”; this is the average height of the adult human male as proposed by Paul Richer after extensively studying the human body, using the human head as a measuring stick. It should be noted however, that 7 ½ heads is not a hard rule, it is an average. Taller people will be more “heads” tall, shorter will be fewer, etc. Measuring with the head using this average will help to ingrain basic proportions and identify important landmarks on the body faster.
Here is one of the charts created by Richer:
Here’s a chart based on this principal made by Adrew Loomis:
Many portions of the body share the same lengths (ex: the length from the acromion process to the bend of the elbow is the same length from the bend of the elbow to the middle of the palm, you can see it notated above by Richer in a dotted line); knowing these will help to maintain consistent proportion in drawing the human form. This, in tandem with the 7 ½ heads average, will aid you immensely with human proportion, and will help pave the way to proportioning other, non-human subjects.
Tackling the muscles of the human body is considerably more difficult but well worth the effort. Just to reiterate, understanding the skeleton helps immeasurably with understanding musculature. If muscle movement is what you’re specifically after, make a concentrated effort to learn where muscles originate on the body, where the fibers stretch to, where they insert back onto the skeleton, and what their function is. Learning about the direction of muscle fibers sounds like excess work, but it is easy to look up and does in itself help to dispel what muscles pull in what direction.
Familiarise yourself with the names and functions of the muscles of the body. Knowing important muscles by name (by their actual Latin name, not something like “arm muscle” - you’ll want to be specific) as well as function will help you to identify those same groups in other people (as well as animals; there is considerable comparative anatomy between humans and animals, but that’s a tangent for another ask) as you observe them. As you familiarise yourself with these muscle groups, be sure to actively look for them when observing, and taking mental note of how they tense, flex, torque, and relax, and draw them in action if you can. Watch sporting competitions, people doing dumb shit on YouTube, people just going about their daily lives performing simple tasks - or even look at yourself in the mirror. Doing ecorche drawings - drawing the musculature of the figure over top a photograph - is also a massive help and will force you to think about what you are seeing. Some examples would be:
Give it a try!
To help you in your studies, here are a few names of muscles and landmarks of the human body that you will want to get to know and commit to memory: Teres Major, Trapezius, Rectus Abdominis, Quadriceps, Greater Trochanter, Acromion Process, Ulnar Furrow, 7th Cervical Vertebra, and Anterior Superior Iliac Spine.
Remember to start small! The human body is pretty damn complex, take it in pieces.
ETA: there were a load of typos in this answer I am sorry. I think I’ve caught them all. That’ll teach me to answer Asks at 12am.