I’ve noticed something lately and I think I’m on to something here:
To emphasize the Lats, do your pullups while contracting your abs through the whole range of motion (and rounding your back).
To emphasize your upper back musculature (lower traps, teres major, rear delts), do your pullups while contracting your lower back through the whole range of motion (and arching your back).
Please try both variations and comment on how you felt your muscle recruitement patterns changed with each one.
I’m eager for some feadback!