I agree with AntiM .. it's the time that you excercise that really counts .. walking is a very good excercise .. partly because, you do it constantly for a while .. and it's easy !! Hey, you get a chance to look around the neighborhood, check out the scenery! It's the time you excercise that counts ... biking is very good ... just try to get your totalk aerobics to about 30 to 45 minutes ... 3 times a week