Last week I was doing some high-rep sets of calf raises and something odd happened. On my 5th and final set I planned to go to failure, with at least 60 reps as the goal. At about 50 reps it burned badly enough that I wasn't sure if I would get 60. But then I did and tried to keep going. At 65 I thought I would try for 5 more, and when I hit 70 it started getting easier. I finally stopped at 85 because my legs were feeling weird. That's when I noticed my lower legs were slightly numb. I could still walk and feel my feet a little bit (less than normal sensation), but it was definitely odd that there was no burning at all like there normally is after a set.
The numbness subsided after about 20 minutes or so, but another strange thing was that I was not sore at all the next day. (I'm always reminded the next day that I did calves the previous day, at least a little bit.)
I did not do calves for an entire week after that. Last night I repeated the exact same workout, but this time I stopped at exactly 60 reps on the last set with the expected amount of burn at that point. Today my calves are sore just like they normally are.
Is there any explanation for this or should I chalk it up to some sort of coincidence that I went beyond burn, which led to numbness, AND I was not sore from that workout?