Just been running and doing normal boxing stuff alot, sparring, millions of situps , shadowboxing, and i feel about 200% faster back when i did weights. I have actually lost half a stone and now i feel alot more flexible and quicker.

I noticed too when I would lift weights for a day that when I went on the heavybag I was throwing faster and so much harder punches with more of a "pop" on them instead of just my normal punches. It might just work for me, but I do recommend throwing in some weight lifting at times.