Stand in front of a step with a resistance band looped around your upper back, holding one end in each hand.
Bring your arms into a "W" position, with your elbows bent and slightly out to the side of the body, and your knuckles pointing up towards the ceiling.
Simultaneously step up onto the step with one leg as you punch your hands up towards the ceiling against resistance.
Pause at the top of the movement then lower back to the start position with control.
Repeat.