As described above, the inferior fibers of the latissimus dorsi muscle display a peak moment arm length at 71 degrees of shoulder abduction of -38.1 mm and a minimum moment arm length at 10 degrees of -3.3 mm. (strengthandconditioningresearch.com)
Jagessar (thesis) investigated the effect of differences in shoulder abduction angle (50, 70 or 90 degrees), scapula position (neutral or retracted), and lower back position (flat, neutral arch, arched) during the bench press. (strengthandconditioningresearch.com)
It's mostly involved in shoulder abduction when the shoulder is internally rotated. (fitnessandpower.com)