Ok...I'm baffled about my recent gains/improvements in my training recently. I was comparing 2 long runs that I did recently on the same (or closely similar) route, one way back in May, the other just last weekend. The route is about 15 miles on mostly flat terrain. May's time was 2:03. (~7:57-8:00 pace) Last week's was 1:55 (7:35-7:40 pace). HR was in the right training zone (140s-mid 150s) though my HR was slightly elevated due to hot weather and dehydration. This is just off base training with mileage buildup from ~45 back to 60 mpw 2 weeks ago with 1 cutback week for every 3 weeks of buildup.The only "speedwork" I was doing during those 8 weeks of buildup were strides and progression runs. Also when I started doing formal speedwork sessions this week the average time for my 400s on Wednesday was faster than expected (1:25-1:26) based on my previous 5k (20:03) and 10k (41:41) times. (I expected 1:30ish or at the most sub 1:30) Is it possible to improve that much on only 8 weeks of base building? Or have I made error somewhere by running my 400s too fast (or my long run too fast?) I still have about 2-3 weeks of base then a 10k race at the end to check on progress before moving to speedwork phase. I find it fascinating to see how my body adapts to training stress.