29 year old male who has been running for four years here. I also recreationally cycle for what it's worth.
I had a 19:45 minute 5k pr off doing 2 tempo runs (7:00 pace) a week, 3 easier sub tempo runs (8:00 pace) and one long run (mixed pace 7:15-8:45 depending on distance/feel) with a couple of strides at sub 6 pace twice a week for speed development. Time trails were also a staple.
I switched my training up in hopes of going for a 17/18 minute pr and did it like letsrunners do it. Lots of base building and easy milage at first, then dropped the volume and added about 3-4 sessions a week of quality/speedwork depending on what phase you are in training. I also train by jack daniels paces during speedwork.
I have lost quite a bit of fitness doing this. I am seriously struggling to even hit 21 minutes in road races now. My workout paces and time trails are really shpwing a drastic loss of fitness too. I've had to drop a couple of VDOTS.
My iron levels are fine, thyroids good and my BMI is flat on 20 and I seriously don't think dropping weight would help as I have been this weight and in much better shape than what I'm currently in. I eat a very good diet with lots of protein and juiced vegetables.
It feels like doimg this time of training has completely deconditioned me. Is it possible that some people just don't respond to running a load of easy milage (for me 8:30-9:00 pace) and thrive more off a harder effort for base? I see a lot of people saying how they dropped minutes just by making their easy paces easier but this just hasn't been the case for me.