overtraining and results

I wanted to ask a question - just out of curiosity. I had a too strenuous training regime a couple of weeks ago and I ended up a bit overtrained. I suffered then from chronic exhaustion and my results became much poorer. All improvement that I had made during the past three months was gone. I started to swim 50m fc at terrifying time of 41-43 secs, though I had already been able to do the same in 38 secs for 50m (not great, I know, but my swimming career is yet rather short). I decided to have a rest. I was going to the pool only two - three times a week, decreased the volume to 1500-2000 and abandoned any demanding tasks. Just leisure swimming - technique and turns. After about 10-12 days I was feeling great. No sign of exhaustion. In fact the fatigue disappeared already after about three days of rest. But then, whenever I tried to experiment with speed and swim one or two 50s or 100s I found my results still as poor as at the time when my exhaustion reached its peak. I could not understand why my body does not want to stand a heavier effort even though my subjective symptoms of overtraining (i.e. fatigue etc) are no longer felt. Now I am back in form - even did my pb at 50m :) (probably because I focussed so much on technique during the past three weeks). Still I am very curious why it was so hard to me to swim faster, even though I did not feel any chronic exhaustion any longer? Is it possible that the effects of the overtraining last still longer than you subjectively experience them?