Dumbbell one arm concentration curl (on stability ball)

Sit on a stability ball with your feet flat on the ground and your knees bent at a 90-degree angle. Hold a dumbbell in one hand with your palm facing up and your arm extended down towards the floor. Rest your elbow on the inside of your thigh, just above the knee. Keeping your upper arm stationary, exhale and curl the dumbbell up towards your shoulder while contracting your biceps. Pause for a moment at the top of the movement, then inhale and slowly lower the dumbbell back down to the starting position. Repeat for the desired number of repetitions, then switch arms and repeat.