Cupped Hands/Palm Straight-Arm Barbell Pullovers
This is the best pre-exhaust lat exercise I know of.
I came up with this exercise after experimenting with the standard barbell pullover. Normally when you do barbell pullovers the palms of the hands face upwards as you lower the bar behind your head. I have found that if you hold the barbell mostly in the palms of the hands, using a thumb-less grip (what I call a cupped hand position), as the bar passes overhead the palms should face the feet. This recruits the lats well and provides a good stretch to the lats.
This is mostly a high rep exercise so do sets of at least 20 reps, up to 50 reps. Use a light weight to ensure proper form. If you go too heavy you lose the isolation effect on the lats. As I said, this is a fantastic exercise to pre-exhaust the lats before any chinning, pull down or rowing exercise. Or you can use as post-exhaust to trash whatever lat fibers are left.
Coach Charles R. Poliquin