For cardio, you could also do top-rope laps. Pick a route slightly below your peak, climb it, descend, climb it, descend, climb it, descend. It's fun to see if

For cardio, you could also do top-rope laps. Pick a route slightly below your peak, climb it, descend, climb it, descend, climb it, descend. It's fun to see if your technical improvement by the third time compensates for climbing slower because you're tired. And FWIW, I've been climbing 2 times/week for 3 years now and have no where near a six-pack :)