100 push ups
It does work well and it builds strength very quickly.
PRs: Boston Marathon, 3:27, April 15th 2013
Cornwall Half-Marathon, 1:35, April 27th 2013
4 years racing, 14 marathons, 14 BQs
A. 5K PR (...well, I just did that)B. DON'T. GET. HURT. (...any more than I already am)