A recent systematic review by Macadam et al in 2015 highlighted the cross over lateral step up exercise. They found that this exercise produced the highest GLUTEUS MAXIMUS EMG activity (103 +/- 63.6%) in their review. Some things to note in this exercise is that it does require a lot of gluteus medius activity as well, as you must be able to maintain good pelvis and knee stability. The elevated femur starts in a relatively adducted and internally rotated position and moves into abduction and external rotation. So we're also adding a frontal and transverse plane component to the normally sagittal plane step up/down.
All the same guidelines apply to the cross over lateral step up as the normal step up/downs that we highlighted yesterday. CONTROL THE DESCENT ALL THE WAY TO THE GROUND. Work on that eccentric control. If you're having a difficult time controlling the descent, try a lower box.