I agree that cross training helps cycling in many ways both physically and mentally. I began an off-season supplemental workout this fall and already am seeing dividends via the power-meter while on the bike.

I have been doing 2:15 circuit intervals using a bike on a trainer as my recovery between each of the four stations. In the circuit I have a Versa Climber, Concept 2 Rowing Machine, upside down Bosu Ball squats with rotating arm positions every 10 squats, and 16" box step ups holding dumbbells. My watch countdown timer is set at 2:15 and it beeps for 10" when it is time to change stations. My hope it to get to the next station and moving within 15" giving me 2' of sustained efforts. I go on the bike with platform pedals between the 4 stations and concentrate on good pedaling form and recovery rather than working hard. I have been doing a warm up circuit then 3 more complete circuits at a hard/sustained pace. Over time I hope to switch up the time on each machine and or increasing the work done at each station.