Great job on the 21:48 – despite the strained hammy. You are absolutely on the right track with your thoughts on how you strained it. I am guilty of hammy injuries myself. My hipside hammy is constantly tight and I am often straining it (I relate that to my partial knee replacement on my non-thr side). I think the best advice that I could give you is to really focus on strength training for your legs (like you’ve never done before) along with some good/regular stretching. It’s a new ball game and you’ll still be able to run, but it’s going to take more focus to avoid injuries. Hope this helps and again….great job with the 21:48.