Called the waiters curl, the variation will emphasize your biceps to the nth degree by using some smart grip manipulation.
Cavaliere breaks it all down in his Instagram video's caption. By resting the flat side of a dumbbell on top of your hands, not gripping the end, and keeping your wrists bent toward the backs of your forearms, youll de-emphasize the forearm flexors and put the onus on the biceps. Raising the dumbbell by pressing through the inner palm will force you to generate consistent supination as you curl. Remember, the biceps arent just responsible for flexing the elbowthey also supinate the forearm, rotating the forearm so that the palms face up.
Like with all biceps curl variations, the importance of good positioning cannot be overstated here ( check out this guide for some more details on that ). Think about pinning your shoulder blades together the entire time. Otherwise, your shoulders are apt to roll forward, which could lead to aches, pains, and injuries over time. A roll forward will also remove some tension from the bicepsand that defeats the whole purpose of the exercise, right?
You can perform the waiters curl with various rep and set schemes, just make sure to take them to fatigue or borderline failure for the greatest muscle stimulus. Also keep in mind that youll use far less total weight that you do with traditional bilateral curls. For example, here, Cavaliere performs his reps with a single 50-pound dumbbell, and were pretty sure can crank out regular curls with more than 25 pounds per side.