The Wolf wrote:
A person who can race a 5k in 15 minutes running 1:15/km slower on easy runs is running at a much easier effort than a person who can race a 5k in 19 minutes who is also running 1:15/km slower on easy runs. You are running harder effort than Sirpoc even if your pace difference between 5k and easy is the same in absolute terms. It's not the same in relative terms.
Don't believe me? Go to the lactrace calculator and enter in 15 minutes and 19 minute for 5k and see if the recommended easy pace is the same gap from race pace. For 15 minutes, it recommends 4:30/km (a + 1:30/km difference), and for 19 minutes it's 5:38/km (+ 1:50/km difference).
That all being said, if you've been training this way for months and have been consistent, healthy and improving, then there is nothing to worry about.
I would like to note, i mentioned it as a speed limit, not an assigned pace. Also, I know people have anointed lactrace some sort of godly calculator, but I’ve tested lactate even after long easy runs at times and +1:00/km has left me at resting lactate levels. Not saying this means it’s optimal for recovery or improvement, but it’s not to say that 4:50/km pace is otherworldly hard and unsustainable for someone running a 5k in 18 flat. I believe sirpoc even says in his early posts that he would run like 5:05-5:15/km when he was in the mid to high 18s and starting the method.