Bayesian Curl

Stand facing away from a low cable pulley with your arm hanging slightly behind your torso rather than at your side. That behind-the-body starting position stretches your biceps further than a standard curl allows, so you'll feel tension even before you start bending your elbow. Curl your hand up toward your shoulder, keeping your elbow pinned behind your ribs rather than letting it drift forward as the weight gets heavier through the rep. Lower back to the stretched position under control rather than letting the cable pull your arm forward. The constant pull of the cable, combined with the extended starting position, is what makes this feel different from a curl done with a dumbbell at your side.