heavier bike + saddle time

[sundial]

So I can do the same workout on my rain/commuter bike, with a full messenger bag and I will be moving slower for the same power output/hr than would happen with my race bike. It doesn't mean the workout is any different, just the speed.

Ok, here's what I'm thinking. Sometime back I read Covert Bailey's Fit or Fat book and he made an interesting illustration. He gave the example of he and his aunt walking the same distance but using different levels of effort. He placed a 5 lb backpack on his aunt while he walked without the backpack. They both covered the same distance but because she exerted more effort, she experienced more work and thus an aerobic benefit unlike his. Granted they both covered the same distance, but she worked harder to get there, thus burned more calories.

That's what has me questioning the heavy bike/distance/cardio correlation.