Here are some quick observations, I hope it helps :) The forearm does look a bit short relative to the upper arm. I would push the value contrast more. Right now it reads a bit flat. The deltoid insertion and the separation between bicep/tricep could use stronger shadows to show that wrap-around form. It look a bit blury the way you shaded. I would commit more. It's a study, be bold ! For the left study, try to commit to cleaner cross-contours. These will help you understand volume better and translate in a better value study later. Watch your elbow placement, atm it feels slightly too low.