Grasp the bar with a wider-than-shoulder-width pronated (overhand) grip.
Hang with your arms and shoulders fully stretched.
Exhale as you pull your body up until your chin rises above the bar.
Hold for a count of two and squeeze your back muscles.
Inhale as you lower your body until your arms and shoulders are fully stretched.
Comments and tips
Pull with your elbows, not with your biceps.
Make the exercise easier by bending your knees and getting someone to hold your feet. You can also use an assisted pull-up machine.
Make the exercise more difficult by wearing a weighted vest or dip belt, by holding a dumbbell between your feet, or by trying some of the numerous advanced pull-up variations (see second video).
The pull-up is a compound exercise that will help you to develop major functional upper-body strength and a wide tapering back. If doing lat pull-downs, your goal should be to graduate to pull-ups at some point. The pull-up is more beneficial than the pull-down because it gets your core more involved, and is more functional and much more versatile.
If you can’t do pull-ups, keep increasing the amount of weight that you pull down until it nears your own weight. Then, practice the negative pull-up (see third video), which will help you to develop the strength necessary to perform proper pull-ups.
If you use a supinated (underhand) grip, it becomes a chin-up.