I just started on this path of the Cool Impossible, specifically working on forefoot strike and adding in some tempo and interval runs. My calves are definitely sore and I'm not too concerned about that since it's, hopefully, just a sign I'm doing things correctly BUT, after my first tempo run last night, I've noticed some tenderness in the left hip bone area. Years and years ago, I had an issue there and ended up having to take months off running. I chalked it up to bad shoes at the time. Discovering Chi Running though, I haven't had an issue since. Any thoughts on what this might be or how to correct before it gets worse?