The Pull Up is a simple exercise to perform and can be modified to suit all levels of exercise enthusiasts. The only equipment needed for performing a Pull Up is a horizontal bar, high enough that you cannot touch the floor while hanging with straight arms. This can be as elaborate as a Pull Up-specific machine in a gym or a simple pole affixed inside a doorway at home. As StrengthUSA.com advises with all exercises, it's important to ensure a proper warm-up and stretching routine prior to all activity.
To perform a Pull Up, start by hanging from the bar with a palms-away grip, shoulder-width apart. Squeeze the bar with your fingers, instead of bearing the brunt of the weight with your palms. -- This will decrease discomfort and painful calluses. Slowly begin to raise yourself up, keeping your shoulders back and leading with your chest. It is important to keep looking up during the lift and drive your elbows toward the floor. Once your chin raises above the bar, slowly lower yourself back down to the starting position. ... You do not want to collapse into this position as it will put dangerous stress levels on your joints and muscles, and can lead to injury.
To increase the difficulty of the Pull Up you can add a weight belt to your waist and increase the load. You can also increase or decrease the width of your grip on the Pull Up bar. Another way to increase the difficulty is to perform the Pull Up with only one arm, but this is only recommended for those experienced in such exercise.
Muscles involved: Latissimus dorsi, Trapezius, Triceps, Biceps, Serratus anterior, Obliques