Originally Posted by DrPete

Doesn't surprise me a bit. There's nothing magical about a bike, and if you constantly do one thing and one thing only for exercise, you're more likely to suffer whatever sport-specific problem that involves. It's a machine designed by people, nothing more. Use it all the time and you're bound to have some problem related to it.

Sure you have to weigh it against heart disease, diabetes, hypertension, etc., but really, there's no rule that says you can't mix it up a bit and go for a run or walk every now and then...