The elliptical (cross) trainer has now replaced treadmill and exercise bike as the most popular device for your cardio training. And not without reason.
It trains your upper and lower body at the same time and by paddling backwards you can use the muscles in your lower body in a different way. You can also use the muscles in your lower body in a different way by adjusting the slope. By increasing the resistance you can increase the intensity of your workout and work on your strength as well as your endurance. Training at a lower resistance, on the other hand, is good for your speed.