That's good tracing. For memorization, just the old practice, practice, practice. Rewatch the video, re-do the excercise, go to the tools/timer section and find references of the back in different positions and trace them and draw them. Then, go back to the video. Things start to fall in their place after repetition. At least, that's what allowed me to memorize relevant muscles. Happy practice!

I get what you're saying! If you're totally new to anatomy it can be overwhelming to try to grasp not only the base form of each muscle, but how they insert and all the different shapes they make in different positions. That's a lot of info to cram into your brain. I've found it helpful to have a reference book open while learning. The first anatomy book I bought was Artistic Anatomy by Dr. Paul Richer and I still reference it to this day. Truthfully, learning and understanding Anatomy takes a decent amount of studying and memorization, but using mnemonics and visual queues makes it more fun and salient. Get creative with it! For example, you can remember the shape of the pelvis by picturing a butterfly. As for muscle grouping, George Bridgman (Constructive Anatomy, Drawing from Life) is a great resource, however some people find it difficult to translate his drawings without prior anatomical understanding, so I would recommend starting with a reference book and working on these tracing exercises, and doing a lot of them. The reps will pay off and the way you start grouping the muscles with the anatomical knowledge you are gaining will become your style!