The pull-up is a key exercise in the development of strength and shoulder health. When done correctly. Many of the issues with pull-ups occur as a result of incorrect shoulder mechanics, often resulting from ineffective methods of scaling. We discuss these mechanics and scaling options in Scaling Pull-Ups With Bands: An Improved Method.
The end point of a standard pull-up is with the chin over the bar. While this position does allow a measurable endpoint, it also excuses poor scapula (shoulder blade) mechanics. It's possible to get the chin over the bar while in scapula elevation (shrugging of the shoulders), meaning the muscles involved in this elevation (upper trapezius, levator scapulae etc) are strengthened (as arm flexors of the elbow), while the important muscles involved in scapula retraction and depression (mid trapezius, rhomboids etc) are neglected.
The shifting of the end point of the pull-up to a chest contact with the bar forces scapula depression. Effectively, this ensures the previously neglected muscle groups are now required to complete a full repetition (and the range at the elbow may also be more - increasing elbow flexor strength). Just like a full squat recruits more lower body posterior chain musculature (and is therefore favourable in most cases over a heavier partial depth squat), a chest to bar pull-up recruits more upper body posterior musculature. This acts to create strong and stable scapulae, and will also fast-track development in associated movements like bar and ring muscle-ups.
Initially, upon introduction of this new standard, and individual will need to reduce loading considerably. By being limited by the ability to generate strength at the end of range, we can begin to even the strength imbalance that exists between muscles involved in scapula elevation and protraction, and those involved in scapula depression and retraction. Long term, this standard will build not only more joint health, but more strength through the entire shoulder girdle, providing benefit to a vast range of associated exercises.