Behind the head Lat Pull Downs are very damaging to the anterior capsule of the glenohumeral joint. This is because of the following reasons:

1. Most Lat Pull machines are not designed with sufficient ergonomics to allow optimal body positioning to do the exercise. Because you generally can't get close enough to the machine to have the cable hang over T1, the resulting compensation is a forward lean of the trunk, which places excessive stress on the shoulder joint in external rotation and horizontal abduction (the exact position which loads the weakest portion of the shoulder joint capsule). Repeated exposure under load will lead to glenohumeral joint laxity, which can be career threatening if you are an athlete.