Ok so say that i run 2 miles, how far would i have to bike to equal that same exercise?

I have a knee problem so my doctor told me that i should bike and not run. And somewhere i heard that riding a bike is easier than running. So i don't mean does 2=2. I mean how do i burn the same amount of calories. Hope that makes sense.

To answer AGAIN, same exercise time at same heart rate = same amount of exercise. In fact your output is easily measured indirectly via HEART RATE.

Further, as I stated, cycling is much easier on your knees, and feet. So maybe that's where you heard cycling is better than running!

Here's a way to find out, if it's allowable for you to do a test run.

Get a heart rate monitor, shouldn't cost you more that $25. Make sure it has calories and average heart rate recall. Do a two-mile at your usual training pace. There's your baseline. What you need to do on your bicycle is to do some rides and compare the final numbers of those rides to the numbers you generated on your run.

It takes me about an hour and a half on the bike to burn the calories I burn in half an hour running, but that's assuming all other things are equal (e.g. hills, headwinds). The heartrate monitor, while not actually measuring calories burned, will give you a more stable indication to use and make comparisons.

I have never found a good conversion formula for that. A lot depends on what kind of bike you are using; a fat tired mountain bike would burn more calories per mile than a slick road bike for example. It would also depend on how hard you went at it; if you just lolly-gagged down the trail, you'd burn far less calories per mile than if you challenged yourself. My best guess comes from my limited jogging experience. Many, many moons ago, jogging a mile would be a farily big challenge; to get that same kinda 'tiredness' on my road bike, I'd have to bike at least 20 miles. Maybe even 30. Using my mountain bike and riding in an area with some hills and other obstacles to make it a good workout, I'd have to go around 10 mi.

This question is a bit more complicated than it looks. I started cycling again a couple of years ago. When I started out, it was quite a big effort to get along at a reasonable speed. Now I easily move at double my original speed with very little effort. That's efficiency. Nobody can compare your output when cycling and running: you might be a very efficient runner who runs fast, or a very inefficient runner who runs slowly and the same applies to your cycling. Just listen to your body: get your heart rate up to the same level as when you were running and keep it there.

I'm no fitness expert, but if we're talking cardio...

figure that you have to spend more time and cover a greater distance on the bike than you would running to build up the same heart rate.

If you go by time, an average person can probably run 1 mile in the time it takes to bike 3, however biking is less intense so it's probably closer to 4 or 5 miles on a bike. This depends on the person and terrain though. e.g. if you live in a hilly area then maybe it's closer to 4 miles if you live some place flat then I'd say 5 miles. hope this helps!

This is not too scientific, but I use 1:2. If you usually run 2 miles, bike 4 miles which should take you about the same amount of time as your 2 mile run. When you are biking, keep the cadence high. 80 - 100 RPM and you will retain most of your fitness.

MR and Rob are pretty much correct. I'd go with 2.5 to 3 miles. But, like MR states you must cycle at the same effort level.

10, 20, 30 miles? no way. That's like saying a 120 mile ride is like running 4 miles - HOG WASH.

I have heard experts use a 5:1 distance ration. You would cycle 10 miles for a similar benefit. My own less than expert observation concurs.