Sit on a preacher bench with a dumbbell in one hand and your upper arm resting on the pad. Hold the dumbbell with a neutral grip (palms facing your body). Keeping your upper arm stationary, exhale and curl the dumbbell up towards your shoulder. Pause for a moment at the top, squeezing your biceps. Inhale and slowly lower the dumbbell back to the starting position. Repeat for the desired number of repetitions, then switch arms.
GIF