It's a great training option for when recovering from many injuries that require less running to heal, but a lateral calf injury is not one of them, at least for me. I thing the reason is that the foot pedals and direction of motion, locked into linear sagittal plane motion, keep your feet locked into a straight line in the sagittal plane which, for me, focuses increased stress to the lateral calf (I normally run with a slightly abducted angle of foot plant which evens out the work to both heads of the gastroc). I learned the hard way.