Um, ouch

So the other day I accidentally ended up doing workout 1B from the New Rules of Lifting for Women. Today, therefore, I decided to do workout 1A. Yeah, what’s your point?
It’s a simple workout; squats, push-ups, seated rows, step-ups and jackknifes. I don’t have access to any kind of squat rack, so I decided front squats would make a reasonable substitute for back squats, and that I’d start light with 20kg. I haven’t squatted in a long time so I knew it’d be tough, and indeed the first set was challenging. What I didn’t expect was the burning, cramping pain in my quads that developed just as I was about to start set 2. Oh my. Apparently I’ve let myself go even more than I thought…
The second set didn’t feel particularly awful, and the rest of the workout was fine, but an hour later I already had pain in my quads that felt like really bad DOMS.
This should not happen after 2 sets of 15 (light) squats, and it does not bode well for tomorrow…