This is an advanced exercise. This exercise combines a step up with a bicep curl.
Steps
Place a box or bench in front of you. Place a dumbbell in each hand with a palms up grip. Keep your back straight, your shoulders back and your abs drawn in.
With one leg, step up on to the box and raise your other leg up (as if taking another step). At the top of the step curl your arms up bringing your biceps towards your shoulders.
Return to the starting position and switch legs.