I have added these back into my training program: single leg barbell step ups. Jill Mills first put them in my programming a few years ago and they are harder then they look (although I feel like I was making them look pretty challenging, lol). The height of the step a total reps is more important than the weight on the bar. Eight reps each side for 2-3 sets is good. Make sure the step you’re using puts your hip below parallel. These work your hip, lower back, upper back, and core. Keep your chest up and drive your neck into the bar as you drive up onto the step. You want your back to stay in the same position it would on a squat. Working each side in isolation doesn’t allow one (stronger) side to compensate for the other. This makes isolation work a good training tool.