Sit on a cable machine with your feet flat on the ground and your back straight. Grasp the cable attachment with an underhand grip, palms facing up, and your arms fully extended. Keeping your upper arms stationary, exhale and curl the cable attachment towards your shoulders, contracting your biceps. Pause for a moment at the top of the movement, squeezing your biceps. Inhale and slowly lower the cable attachment back to the starting position, fully extending your arms. Repeat for the desired number of repetitions.
GIF