I’ll bite as someone who trained way harder than he should have using Paavo in high school in the early 2000s.
It was the first training system I ever knew existed and I spent my first year only following it with about 50% commitment (frequently lying to my coach, along with 75% of the team) about how far and fast I’d done my “medium pace” runs, for starters. I didn’t climb up the “steps” very fast either and thus my weekly mileage stayed in the 20s and 30s, meaning my “long fast tempo” runs weren’t yet ridiculous.
Then I realized I was pretty good and wanted to be great, something clicked and I bought in 100%. Thus commenced a vicious cycle — I religiously did my all-out timed mile every Saturday and used that to base my “medium” (100 seconds per mile slower than the timed mile) and “fast” (54 seconds slower per mile) paced training run.
Say I had run a 5:00 timed mile by myself on Saturday morning with my watch. I would then go out and run, say, 8 miles @ 6:40 pace. Since I was now up to ~40 miles a week, I would run 3 miles on Tuesday afternoon at 5:54/ mile and then on Thursday I’d bust my ass to run 6 miles at 5:54 pace. Monday was the easy long day — 10 miles at whatever pace I wanted and over time I began pushing that to try to eke out more aerobic benefit. Everything else was 6:40/mile.
At some point my coach recalled a top star of his from years earlier who ran 80+ miles a week at sub-6 pace. This became the North Star in my head and as I got faster, I pushed my medium paced runs faster and faster to try to get to that. (Thus I pushed Paavo even harder than Paavo intended to be pushed and was lauded for my efforts!)
The truly brutal point came when I’d finally reached Step 6 and thus was expected to knock off 8 miles every Thursday at sub-6 pace.
How did this play out? I was among the best in my conference but never could win a conference title in XC or track. Always out kicked or having fallen behind.
I’d thrive mid season and set PRs. In fact, the whole team seemed to peak halfway though the season. By championship time, other teams using Jack Daniel’s would suddenly BLOW by us and we’d be utterly confused. Over time I started betting surpassed by people at other schools that I knew I was better than.
By senior year I and my buddies had lost faith in the system and our coach. We tried various other approach we read about on these forms (Hadd etc) and realized about Jack Daniel’s only when it was too late — outdoor track senior year.
Anyway, I can’t say that Paavo was completely destructive. But I would say it’s far far far from optimal and there’s no point in going with the program, unless perhaps you have a coach capable of keeping everyone in check…but such a good coach would no doubt reject Paavo for something better in the first place