CC82, I've hit 100 mile weeks running, I've tried 50 miles running + 100miles on the bike. Last year I averaged 10 miles/day for 6 months.
I've also reverted to one long a week and two speed sessions.
And sometimes just sessions, rest and races. Always the same.
At sub-maximal paces I can cruise along without apparent effort. But speed always makes my lungs explode. In fact, in 25 years of running I can only remember one occasion (Richmond Summer league relay 1000m 1994) when I ran fast the whole way without my lungs reacting.
If I tried an 800m at a pace I should manage, my lungs crash in 30 seconds along with everything else. I have to slow down.
The only explanation that I've ever come up with is that I haven't an ounce of anaerobic capacity in my entire system. Almost zero.
I can operate on the edge of it but no further.
In a race (distance) I could be comfortable, almost. If I tried a surge for even 5 seconds, I'll blow up bad enough to almost have to stop.
I see - it was just "out of interest" really as you'd mentioned a few times that your mileage was quite low recently.