4. The Atlas
Targets shoulders, arms, abs, butt, and legs
Standing on step with right leg, hold dumbbells with arms extended out to sides just below shoulder level, elbows slightly bent and palms up, and bend left knee 90 degrees in front of you; start with left knee just below hip level.
Raise arms and left knee a few inches simultaneously (to shoulder and hip level, respectively), then lower to start.
Do 10 reps; switch sides and repeat.
Do 24 reps, alternating sides.