This accessory exercise for the deadlift will strengthen your spinal erectors. This helps you to deadlift heavier while keeping your spine stable and safe.
Deadlifting heavy gets a bad reputation because some people get injured. But the most common injuries come from bad form and/or the spine alternating positions throughout the lift.
Rounded thoracic RDLs will allow you to introduce spinal flexion under small loads. And they'll help you gain the strength you need in your spinal erectors to protect the mid back and up.
An important factor is allowing your scapula to protract and retract to its full extent as well as creating as much spinal flexion and extension as possible.
Didn't it seem that the bodybuilders of yesteryear had bigger chests? (We're talking chest circumference here and not pec size, mind you.) Ellington thinks so and he knows why - it was all due to the all-but-lost art of ribcage expansion.