I don’t. Zero, zip, nada. Nor does John Smith. I run them all out of blocks.
In terms of recovery, John Smith uses ~4 min after each, and from what I’ve read Pfaff uses 4-5 min. Mine is very definitely a split run with just walkback rest for reps and a 1 lap walk for set break. Builds up power which you can use later when you start doing 60s Charlie’s way with longer rest.
BTW, while doing, say, 3X5X40, I’ve had a couple Jamaican coaches on the same track explaining (correctly) to their athletes exactly what I’m doing and why, so I don’t think I’m the only person doing this.