Sit on a bench holding a moderate-weight barbell, gripping with palms facing up, inside shoulder width. Curl bar to chin height. This is starting position.
Lower until arms are bent 90 degrees; curl bar up.
With bar still at chin height, fire through glutes to stand up, then lower bar under control to full extension.
Curl bar back up to chin height, press it overhead, return it to top of curl, then sit back onto box.