Very interesting thread.

I have personally experienced the ratio to be more like 6 or 7 to 1 assuming a geared bike. Some of that is probably because I don't run too much, I'm asthmatic and I'm a clyde at 6'3, 205. I run comfortably at a 9:30 mile, and can do that for 7-10 miles easily enough. When riding, I average 15-17 mph, and typically ride 35-80 miles at a time.

That said, in terms of intensity of workout and impact on the body, I've started riding fixed a fair deal. For me, using distance, it's closer to 3 or 4 :1 fixed vs. running, moderate hills and a ratio of 46x16 on the fixie. Anyone else ride fixed to train, and have an opinion on the ratio?