I think the name “531” name is confusing you, because it really no longer describes the program or progression very much. You are expecting the “3x3” week to have have three sets of three, and with most programs, like Krypteia, you are using 5’s PRO and everything is 5x5.
So, the only difference between the 5x5 week, the 3x3 week, and the 531 week is the percentages. You are not “changing your TM” from week to week, just using a different percentage of it.
TM = 200 lbs, let’s say.
Week 1 (5x5). Your working weights are 65, 75, and 85 percent of that. So, you’d do 5 reps at 130 lbs, then 5 reps at 150 lbs, then 5 reps at 170 lbs. Then, you’d do your FSL, which is 5 sets of 5 at 130 lbs (the weight of your first working sets.
Week 2 (3x3). Your working weights are 70, 80, and 90 percent of 200 lbs. So, you’d do 5 reps at 140 lbs, then 5 reps at 160 lbs, then 5 reps at 180 lbs. Then, you’d do your FSL, which is 5 sets of 5 at 140 lbs (the weight of your first working sets.
Week 3 (5x3x1). Your working weights are 75, 85, and 95 percent of 200 lbs. So, you’d do 5 reps at 150 lbs, then 5 reps at 170 lbs, then 5 reps at 189 lbs. Then, you’d do your FSL, which is 5 sets of 5 at 150 lbs (the weight of your first working sets.
That’s it. So you’re right in that 3x3 is a bit of a misnomer. Also, note I didn’t put in the warm up sets, but do those too.
This would be what’s called a “leader”, and what is listed above would be one cycle. You would typically increase your TM by 5-10 lbs, then run it again the same way but with these new (slightly heavier) weights. That would be your second cycle of a leader. You would typically take a week here to deload or test, and Jim calls this the 7th week protocol. Finally, increase your TM again and run it again. The only difference is that you push the heaviest set for a personal record each workout.