Short answer: Nope!
Using an elliptical machine or cross-trainer is a close substitute for walking or jogging on a treadmill or outside. Your body should move in roughly the same way, whether you’re walking around during day to day life, cruising on the treadmill, or turning the pedals on an elliptical machine.
When you walk, jog, or run, your heel leaves the ground as your back leg powers you forward. This same movement is used with an elliptical trainer. The main difference (obviously) is that you don’t actually go anywhere. To get your workout in and heart rate up, you still have to move the pedals, which requires the same “push” from the back leg that you use to move yourself forward when walking or running. (If you’ve tried using the crosstrainer with your heels stuck flat, it’s probably felt kind of awkward, yeah? That’s why!)
That doesn’t mean that you should spend your whole workout without your heel on the pedal – that would be like walking around on your toes all the time. Your heel should lift at least slightly as you bring your back leg forward, and be in contact with the pedal as your leg moves from in front to behind. How much acutal “lift” you get will depend on the machine you use, as some have a more oval-shaped pedal track, which will require more heel lift, and some will have a more circular pedal track, which might have little lift, or even just a shift of your body weight onto your toes.
The heel lift is part of your normal stride or gait. But it’s just one piece of the puzzle in efficient walking, running, or crosstraining. Lifting your heel as your back leg prepares to swing forward helps connect your foot and ankle with the other muscles in the back of the leg, and through the back to the opposite arm (using an opposite arm-leg swing pattern helps us stay balanced and not falling over). The muscles of your calf contract to lift the heel and push the foot into the ground, working in a coordinated pattern with the other muscles used in your stride pattern. Changing the way you move one part of your body (or prevent movement) can greatly impact many other body parts, and may predispose you to higher stress and strain on your soft tissues and joints.
I’ve answered a similar question over at Quora if you want more info. But your best bet? Let your body move naturally. If you’re not in pain during or after your workout, you’re likely ok!
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