Preacher curls

Adjust the preacher rack so that you can comfortably bend your elbows and so that your body can be positioned in an angle away from the rack (if standing).
Hold the preacher bar with straight arms, breathe in, and flex your core.
Breathe out and pull the bar upwards until you are just above a 90 degree angle with your arms.
Pause at the top.
Breathe in and lower the bar back towards the starting position for 2-4 seconds and extend your arms as much as you can with control to get a deep stretch in your biceps.