I started running again in March after a long break, but have made significant progress. (I'm a mid-30s former college runner that focuses on weight lifting these days but like to go on the occasional turkey trot)
March:
Started off on 20mpw, doing 3-6 mile runs at around 9-10 minute pace (slow I know). Ran a 10K in March recording a 43:30.
April:
Increased to maybe 25-30mpw, doing 4-8 mile runs at around 8:00 minute pace (still slow I know!) with an occasional tempo. Ran another 10K, did 39:20ish. Big improvement!
May:
Increased to 35-40mpw, doing mostly 6-10 mile runs, around 7:30 minute pace mostly. I do 1 tempo (or close to tempo) run each week, 1 long run of 12 miles and have done 2 interval sessions. I have made huge gains in both training and race times. I recently did a tempo run on my own where I ran a 10K in 40:00 flat, so I expect my fitness to be around a 37-38 10K.
Problem:
However, I am feeling tired constantly. No injury yet, none of the classic overtraining symptoms. I eat well, sleep well, take plenty of supplements and have only lost maybe 5 pounds since March (starting point of 165lbs). But my legs feel shot. Just yesterday, I went for an easy recovery run. I was slogging through 6 miles at 8:30 pace and sweating bullets. Just the day before, I did 12 miles at 7:00 pace. I've also done a few 6-8 mile runs at 6:30-7:30 pace in the last week.
So I know I'm much faster than I was a month ago based on my workouts and hard running times, but my easy and recovery runs have gotten slower and/or harder! What's going on? It has gotten significantly hotter where I live, so could it be the temperature? Or is this a sign that I need to start losing weight? I carry a lot of upper-body muscle.