But aren't we trying to avoid a pull?

Where does the pull up fit into developing as a runner?

Well, Arthur Lydiard prescribed 20 pull ups every day... Every. Day.

If we're going to express proper running form with a straight, upright  posture then the musculature from the base of the neck, to the top of the butt need to be in good form. The pull up is a movement that develops the latissimus, trapezius, biceps, rhomboids, and all the musculature of the posterior deltoid. Let's start from the top:

The trapezius is not a primary mover in the pull up, but they function to depress the scapula during the movement. When running, the shoulders need to be depressed in order to provide optimal range of motion, when they shrug up (as they often do when fatigue sets in and form goes to pots) range of motion is limited which causes sway back and excessive hip rotation to counter the lack of movement in the thoracic spine.

The rhomboids function similarly to stabilize the scapulas and the rest of the thoracic spine in maintaining an upright posture.

The muscles of the posterior deltoid are developed as well, and they function to provide the backward portion of the arm swing as well as maintain stability in the shoulders and posterior clavicular complex. Not only is this vital to proper form, it also allows the lungs more room to function making breathing easier.

The biceps are major movers in the pull up, but only function minorly in running. They assist in maintaining arm carriage and the high insertion of the biceps also provide some of the forward movement of the arm swing.

Finally, the latissimus dorsi are the major movers in the pull up, and have a major function in running as well. The latissimus are major stabilizers of the entire posterior chain and function to depress the shoulders and scapula. By providing stability of the posterior chain the latissimus allow the hips to maintain a more natural position. Also, with the depression of the shoulders, they are better able to move through their range of motion naturally, which prevents you from having to fight your own body mechanics.

Pull ups are a difficult movement, to be sure. However, they pay off when you do them frequently. I prefer the strict pull up as a means to develop strength in the posterior chain. There are variations of pull ups that allow for assistance (kipping, band-assisted, butterfly) and these are good for beginning to develop pull ups, but over time they lose their application as a strength building movement. So when kipping pull ups get to be standard, it's time to start adding strict pull ups. When reps prescribed are higher, it's acceptable to break single sets into smaller sets with as little rest as possible. The importance is not the speed of the pull up set, but the integrity of the movement and the completion of the volume.

Pull ups - as abhorred as they are - should be embraced as a weakness for many runners and attacked with the ferocity that you would attack a lack of a kick, or a need to develop more stamina.