The EZ bar preacher curl is a great exercise to isolate the biceps, while minimizing the strain on your wrists. Adjust the seat on the preacher bench so that your upper arms sit comfortably on the padding when seated.
Load the desired weight on the barbell.
Sit on the preacher bench and grip the EZ bar with your hands shoulder width apart using an underhand (palms facing up) grip. (note: You can use a wide or narrow grip on this exercise)
Keeping your back straight and eyes facing forward, take the weight off the rack so that you’re supporting it with your arms slightly bent. This is the starting position.
Slowly bring the weight up until your forearms are at a right angle to the floor.
Squeeze the bicep at the top of the movement, and then slowly lower it back to the starting position.