Take 2 dumbbells. Stand with your legs shoulder width apart, bend your knees slightly. Let your arms to hang down with your palms facing each other.
Moving only your forearms, slowly curl the dumbbells up to shoulder level. Turn your palms up when they pass your thighs. Keep your elbows pressed against your sides throughout the exercise.
Hold this position for a moment and slowly lower the dumbbells. Turn your palms in when they are halfway down. Make sure that only your forearms are moving throughout the exercise.