Quadruple GainzZz! WTF??

[Fiddler]

Background: I'm smallish, old, and have been nursing a torn-up shoulder (muscle / tendon damage from a fall, no surgery) for over two years. Squat and DL are pretty good (CL1 - Master level for my age) but presses lag far behind. I've been doing Andy's 5-3-1 over 40 program since June.

Usually, it's a grind for me to gain 2.5 lbs per 3-week cycle on my presses. It's singles week, and today I went in to do a bench press weight that I had failed on 3 weeks ago. Warmups didn't feel that great, but I loaded up my planned weight and it went up OK. Twice. Third set, I thought "that wasn't really a max effort," and added 2.5 lb to the bar. That went up OK, too. So I did a fourth "set" (if 1 rep is a set) with an additional 5 lbs on the bar. It went up, too. Tried another 5 lb after a suitable wait, but the magic was gone. Still, 10 lbs increase where 2.5 is usually a grind???

This has me puzzled. According to the rep calculators and the pattern I have established for the past few months, I should have been able to do the planned weight, maybe 2.5 pounds more than that on a really good day. But I got four times as much progress as I had anticipated. Nothing really different from usual. Usual routine, OK food, OK sleep, but nothing special. Wasn't feeling all that great. I'm thinking my shoulder maybe just reached a point in its healing where it suddenly got a lot stronger; I noticed that I didn't have to "fudge" to get the weak side up. Is that something that happens on these long, long rehabs? Of course, it's also possible that I was just having a good day, but that's a Hell of a good day for me. (BTW the dumbbell presses I do after bench presses were quite a bit stronger, too - 5 reps last week, 10 reps this week.)

Has anybody had similar experiences, or an explanation? I'll definitely take the gains, but I'm sure curious to understand what's up. I'd like to repeat the process if I could.

[melody]

Sometimes you have a good day, just like sometimes you have a bad day. Enjoy it!