Stand with feet wide and hold a single 8-pound dumbbell with both hands overhead, arms extended. Shift body weight to left leg as you pivot on right foot and rotate torso to left (reaching even higher with dumbbell). Then bring dumbbell down beside right hip as you raise bent right knee to hip level. Reverse motion, returning to reaching upward toward left, to complete 1 rep. Do 8 to 10 reps. Switch sides; repeat.
Start on floor in plank position, body balancing on hands and toes. Keep hips level and bend left knee out to side toward left triceps. Return to plank, switch sides, and repeat to complete 1 rep. Do 2 sets of 10 to 12 reps.