Barbell Preacher Curl

The preacher curl isolates the biceps as strictly as any curl can, by bracing your upper arms flat against the angled pad of a preacher bench. With your arms pinned in place, there's nowhere for momentum to hide: the biceps have to do every bit of the work, especially through the stretched bottom of the rep where the pad's angle loads the muscle hardest. That makes it a favorite for building the lower part of the biceps and for anyone who tends to cheat standing curls with body swing — the bench simply won't let you. Run with a straight or EZ barbell, it delivers a deep, focused contraction. The trade-off comes from that same locked-in stretch: overloading the bottom position can stress the elbows, so leave your ego off the bar, and it trains only the biceps rather than the whole arm. Lower under control all the way, don't bounce out of the bottom, and keep the reps strict. As a targeted biceps builder, it's about as clean as it gets.