This is a good example of the Squat Assisted Pull Up (or Squat Pull) using playground equipment.
Though the author Ed Pierini offers some suggestions, those wishing to use them as a “panaerobic” exercise in the way suggested by Dr. Schwartz might do them for timed continuous reps (working up to 15 minutes or more) or even as ”intervals” such as 30 seconds of as many reps as possible alternated with 30 seconds active rest. That combination might be repeated 10 or more times.
Dr. Schwartz also envisioned these being done at a “Pan-X” device (patented as a “Strength-endurance exercise apparatus
US 4932653 A”) where it was possible to move from this exercise after 2 minutes to other exercises using as much overall muscle tissue as possible (not isolation exercises done in a “Circuit”).