Do a stretch-based back movement before any big pulling exercises on back day. This "primer" exercise reverts your body into a normal posture by getting you into the opposite positions you most likely spend most of your day in.

The single most effective movement to prime the back is the straight-arm pulldown and its variations. This movement involves isolating the latissimus dorsi. In most cases, it's functionally shortened. Doing both an end-range stretch along with a peak concentric contraction works wonders.

Straight-Arm Pulldown

The straight-arm pulldown is based on internal tension. If you're using a cable stack, it's less about the external load you're placing on the tissues and more about how you're building and bracing your tension throughout a full range of motion throughout the set.

As you'll see, this movement will be humbling, so make sure you set your ego aside and train this exercise for the feel and pump.

Related:  More Primer Exercises to Boost the Big Lifts

Related:  4 Exercises for a Thick Back