I've been doing the core work from PUB regularly lately (re pikes, I went from not being able to balance on the ball to being able to do every other pike. My aim is to do all of them). I've never been able to do pushups on my toes before. Anyway, I was viewing P90X chest and back at the weekend, and I decided to see if I was any better at pushups on my toes - I did 10 with relative ease, then stopped because I started to feel my back sinking (ie started losing my form). I am so pleased. I would recommend core work (planks, etc) for anyone who struggles with pushups.
Shaz
Shaz