Zone 2 running pace not improving despite increase in overall fitness
Howdy y'all, I've (25M) got a training question
As the title suggests, when training for long times on end (I typically increase training volume for 2 months and I'll take a couple weeks at a lower volume to recover, then increase the volume again) my zone 2 pace doesn't seem to move much.
It's this weird phenomenon where I'll train 10-15 hours a week (divided between running, cycling and (alas) swimming). My general fitness will skyrocket, my resting heart rate drops, my cycling fitness (both threshold and zone 2) increases steadily, swimming's still swimming and my running threshold pace moves along nicely. (Went from 5.10min/km-ish to 4.30min/km, over a prolonged period of training). But despite all of this, my zone 2 running pace just seems to be stuck.
I started out at about 6.30min/km, it feels VERY easy, my HR would be around 155. Mind you, I have never done any lactate testing, but I can go on forever at 6.30 and at that HR I have no HR-creep whatsoever (unless in extreme heat). My threshold HR has stayed the same, but as said my pace has increased by about 40sec/km. Yet my zone 2 HR/pace just won't budge. It'll be 6.10min/km at times, but that's just on a good day. On a bad day it'll be 6.30 again and sometimes my HR will randomly skyrocket to about 165bpm.
Last summer I thought to myself ''hmm, maybe I should just do even more volume at zone 2", so I scrapped all of my tempo workouts and replaced them with long runs, had 2 long runs every week for a couple of weeks, with some shorter (also easy) runs throughout and then also cycling (peaked at about 50k/week of running). Result: my tempo pace increased even further and my zone 2 stayed the same again. It moved by like 10s, if even that.
So, I'm puzzled. Everything always seems to point in the right direction, all of my paces are increasing. Yet, my zone 2 seems to be going absolutely nowhere. I'm convinced all of my buddies are running their "zone 2" in zone 3, because they'll get home from an 8k absolutely blasting their breathing and sweating like a wild horse, flaring their nostrils,... And I'm over here, getting home from a 15k with next to no fatigue, so I'm really willing to guess I'm not in zone 3, yet adaptations seem to be odd.
Weird thing then is, my race pace is faster than ALL of my friends' pace. I'll always finish before them. Even though their "zone 2" is a minute faster than mine and their intervals are generally also run at a higher pace. Although, same thing there. I think they are running their so called "threshold" fully anaerobic. But that's just my idea, idk.
Are my expectations just too high? Is zone 2 pace not supposed to move a whole lot? I don't think I'm running zone 1 either, given that I'm still very much an amateur?
I'm puzzled. It just seems odd. I ran a 1.39 half marathon, which I find fairly decent, yet my zone 2 pace is chugging along with the grannies at your local park, lol.
Any advice is appreciated 😄 Thanks so much in advance!