The HR strap (old style Garmin) got me in the left side just outside of being below the boob. I wonder if I didn't have the little tab in all the way (or whether it rubbed when I was stretching).

Calf Pain: I don't think it's a nutritional deficiency. I'm hoping it's just a combination of the fact that I've been running 3 weeks and I'm doing this program in barefoot shoes (though I have been walking in them for 2 years and doing gym workouts in them). No foot pain with them (new!), so I really don't want to go get fitted for a traditional running shoe. It feels like the calf is too full and tight - it's not really a cramp per se. Both are affected, but the right is much worse. Very odd, and not something I've encountered biking (but have had walking fast up hill).