Increase metabolic stress and time under tension with this mechanical drop set. Instead of dropping the weight, you'll be using an "easier" variation of the same exercise as you fatigue. The weight on the bar stays the same.
Set up at a preacher curl bench with an EZ-curl bar. Use a weight that you could curl 12-15 times. Do 8-10 reps on the steep, vertical side of the bench. Hold each rep for a 1-second contraction at the top.
Move around to the angled side of the bench and try to match the rep count from the first part of the set, with a slight pause in the stretched, bottom position of each rep.
Now stand up and rep out as many curls as you can.