I was a bit ambivalent about using them today, but I'm glad I did. My previous sprints were done on flat ground, which is probably less safe than running uphill even if it takes more effort. I'll do hill sprints next week again.
I'm vaguely following the Primal Blueprint exercise program, but as encouraged, I'm not being very strict about it. It's been the most natural way to keep fit I've ever tried, I don't feel bad if I skip a workout. I only workout when I feel like it. I don't go to gym, I do pushups, squats, pullups and planks at home. I don't let myself get tired, when I start getting tired I stop. I don't do ANY distance running anymore, which I realise now made me very tired and was probably not suitable for someone with a cardiac history.... or anyone for that matter. I walk lots, and from yesterday, I dance once more. Can't think of any better way to keep fit!!