String ring pull-ups are a bit of a novelty in my mind. A way to add variation. A way to break the monotony. A way to make the same-old pull-up a little more arduous, but not too much of course.
Other than a change in pace in exercise selection, there are a few different reasons you might want to rotate ring pull-ups into your routine.
First, you may need to get better at being on the rings for whatever reason. Let’s say you want to do muscle-ups, levers, tucks, skin the cats, or other adult-themed gymnastic movements; it may behoove you to dedicate some extra time to the rings. The rings are a finicky apparatus needing additional balance and stabilization compared to its affixed brethren. Any spare time spent on them will help you adapt to rings.
Second, you may have stalled out on your strict weighted dip pull up routine. Let’s say you’re doing Starting Strength or Lean Gains and you’ve stalled out on the progressions for pull-ups. You’re eating enough. You’re sleeping enough. All the boxes are checked. If this is the case for you, ring pull-ups might be an excellent exercise to rotate in for a few months to help break any plateau.
To learn, checkout the Definitive Pull-Up Guide. Additionally, the string ring pull up shows up on the pull-up program below.