The day after the day after

Question: When I haven't been to judo in a few weeks, I'm more sore 48 hours after practice than I am 24 hours afterward. But after getting back in shape the soreness seems to constantly decrease with time. Other people tell me similar things with other new exercise regimes. So I don't think I'm idiosyncratic. Why does this happen?

My initial thought --and here I reveal the depth of my ignorance-- was that since the tissues have been healing, the worsening allodynia isn't due to increased prostaglandins, bradykinin, leukotrienes, etc, released by the damaged muscle. Rather it's from dorsal horn wind-up, and neurogenic inflammatory factors like substance p and neurokinins A and B. It makes sense that those would continue to increase over time.

But that wouldn't explain why this doesn't seem to happen when I'm already in shape, even when a workout is much harder than usual.

Or is it just the obvious answer that the difference between relative inactivity and a moderate workout is less than the difference between a moderate workout and a really hard one?

Ideas?