A foot cradle apparatus of a muscle training device is provided, having a foot cradle with a tread and a side wall at least partially limiting the tread, and a fixation unit for fixing a human foot in the foot cradle. A foot fixation unit that is simple to handle and has small dimensions and a low weight is created in that the fixation unit is formed as a lockable, pivotable bracket, whose pivot bearing has a pivot axis oriented substantially parallel to the longitudinal axis of the foot cradle and is provided in a compact bearing unit which is connected fixedly at least indirectly to the foot cradle and which is attached to an inner side wall, close to the inner side of a patient's foot, of the foot cradle and is connected fixedly to the tread via the inner side wall.