Cycling can be an intensive fat burner. Try to pace yourself with 80 to 100 rpm. There are digital computers you can attach to your bicycle to keep track of your rpm and mileage. You will ride faster before you become tired, but put less strain on your knees. Your pace can easily be determined by calculating how many times the right leg rises up in ten second increments. Once you have this number, multiply it by six. Try to maintain this rpm.