Rack Pulls and Block Pulls allow us to pull some very heavy loads for a reduced range of motion. This has the benefit of being extremely stressful to the central nervous system (i.e. we get good at straining against super heavy weight) and also directly targeting the lumbar muscles in a way that no other exercise even comes close to. The downside to Rack Pulls and Block Pulls is the same as the upside they fry our CNS and our lower backs.
For this reason, they must be used with extreme care. Frequency must be limited to every other week at most, although I think once every 3rd week might be even better for longer term usage. When you go all out on a Rack Pull it takes a while to recover. Ive seen guys come in and pull 600ื5 on and the following week they cant budge 500 off the pins for a single. You cant do them heavy weekly. Rack Pulls should be rotated with regular deadlifts or with other deadlift variants explained in this article as part of a rotation of movements that get included in a lifters heavy pulling day.