I don't know if it's a "WTH" effect (and I'm still struggling with English).
I've started ROP the 01/09/2016 with a 16 kg for the clean&press (it was my 12 RM) and a 24 kg for the swings (I believe that my PR was 10*10 swings in about 6 minutes). I lost a bit of fat and added a fair amount of muscles on my abs, glutes, back and shoulders.
I received my 32 kg KB the 22/05/2017. After reading
this Reddit post, I thought it was a good idea to do one-handed swings with it, 2 reps on the minute for 10 minutes. My goal was to get used to the 32 kg bell. Then I added some time (20 minutes was my target). And then I added reps (5 reps was my target, but I'm still at 3 reps now). I did those swings during the "rest/play" day, that is around 2 - 3 times a week, which is 11 training session until my new PR (see below). Despite the "heavy" weight, I wasn't burnt after the swings, my hands are still a bit painful because of the weight (my hands are soft), but that's it. I remember the first time I used this bell for the swing (the 23/05/2017), it felt heavy.
I gradually added the 32 kg in the main ROP training. I'm know only using the 32 kg.
The 18/06/2017, I did 10*10 reps in 5:08 with the 32. My technique wasn't great (my breath wasn't in sync for about 7 reps), but my grip was good enough, the problem was my hearth and my lungs. I think that in two or three months, I shall do it with a good technique.
Also, yesterday I was impressed by my arms: they are bigger than before. I think it's the heavy swings that did that, because they feel a bit sore after the Hard and Medium days.
I noticed that I run faster (or my acceleration is greater, I don't know). During a thrash metal concert, I wasn't bothered by the pit: I had enough strength and endurance do stay in it.