Good start. I would recommend you use flowing lines, particularly if the body is bending and/or tristing. It would make for a more interesting picture. Expand your practice to the many photos provided by Line of Action or On-air Video. Also, do longer sessions. Plus, do many more. On your own, study human anatomy - both muscle & bone structure. Make drawings of these items. The internet has a lot of information on these subjects.
Remember: Practice makes better. So, practice, practice and practice some more. You will find in the long run, it will pay off in your work.
I like the 60sec practice. From 30sec I suggest to use more S lines, you can exaggerate the pose to make it more dinamyc, remember that the body isn't a box, so try to avoid straight lines and think on them like circles or ovals, at least meanwhile you learn to know how to overlap, overlaping helps a lot to reach the 3D look.