If you've been following my advice and thinking in terms of "chest-ups" rather than "chin-ups," you may have felt the effects of last week's back day long after you left the gym. You wouldn't be the first!
What can I say? I'm a stickler for form when it comes to the upper back, perhaps more than for any other body part, and the reason is simple: Most people don't do enough high-quality back work to counteract their pressing.
This week, dig deep, pin those shoulder blades back, and keep your torso rigid, particularly during the single-arm rowing work. You'll need the strength and stability you're building now when we switch to pull-ups—or "prone grip chest-ups," as you'll be performing them—and T-bar rows next week.