Dumbbell triceps kickbacks are not ideal for hypertrophy (muscle growth) for a few reasons: 1.) The limiting factors are going to be gravity the strength of your shoulder adductors, not the triceps. 2.) The triceps are only going to be working through a very short range of motion. 3.) It’s easy to rely mostly on momentum and minimal muscle contraction. Instead, skull crushers, cable push-downs, and dumbbell overhead triceps extensions give you more bang for your buck. Stop wasting your time with this exercise.