What burns more calories, walking 4 miles or riding a bike for four miles? Which is better for muscle development?

I would think that the bike riding would be very beneficial for muscle building. Although the absolute best exercise is swimming.

You can sign up at Free Diet Plans at SparkPeople. They have an exercise calculator that gives the amount of calories burned for most activities. It's a pretty good site.

Well, if you use the bike then you'll do the 4 miles in less time, so you can ride further in the same time! :)

If you only do 4 miles then walking because the bicycle is a very efficient machine. However if it was the same amount of time it would depend on how fast you cycle.

Cycling can be a great way to work out as you can get the cardiovascular workout of running without as much joint strain - but you'll have to do more than 4 miles.

Cycling will be better for muscle development as you will have more resistance especially if you cycle uphill.