If you run for a long enough period of time, you will eventually reach an age where you stop getting faster. That age is probably different for everyone though. I’m too lazy to look it up, but I remember reading a while back that runners typically start slowing down after about 8 years of consistent training. Given that I turned 51 late last year and have been running for just over 10 years, it’s reasonable to assume that my fastest days are behind me.
Unfortunately, reasonable people don’t run ultras.
There are theoretical and practical considerations as to whether I’ve already run my fastest races. Theoretically, I could dramatically ramp up my training volume and intensity. I’m a 50mpw hobby runner who does no speedwork and minimal strength training. A 40-50% increase in my mileage with speedwork and a consistent strength routing would undoubtedly take my fitness to an entirely new level. PRs would be a natural results, especially at those distances that I’ve never really raced well at before (I’m looking at you half marathon). Another natural result would be burnout, either physically or mentally. This is likely a card I will eventually play, but not until I’m retired and can devote more time and energy to training.
One of the practical aspects of endurance sports is that the further you go, the more experience and adaptability come into play vs. pure fitness. It doesn’t matter how much experience or savvy you have as a runner, your 5k time is going to be 95% correlated to what shape you’re in. Marathons are probably 80% fitness and 20% managing your pace early on. By the time you get up to 100 miles, fitness may only be 50% the name of the game. Hydration, nutrition, pacing, blister prevention, weather management, and a host of other challenges need to be met in order to get you your hard fought buckle. Many of these challenges only arise during races themselves so the only way to gain the experience you need is to encounter them in races.
A couple examples. You’ve probably run in rainy 40 degree temperatures before and you’ve probably got your gear dialed in for that. But there’s a big difference between a 3 hour long run and many hours of rain twelve hours into a run when your body stops being able to regulate it’s internal temperature. If you’re from sea level, then you never know how high altitude will impact you until you give it a try. And just because your nutrition plan works for a four hour run doesn’t mean it’ll work for a 34 hour run.
All of this being a long winded way of saying I think I can squeeze some time off my 100 mile PR without going crazy with my training. Now I don’t think a better executed race will drop 4 hours off my time, but a tweak here and a tweak there can probably save me 45 minutes to let me dip under 20 hours. Maybe. I’ve got a nice training block planned out and a flat course lined up to give it a shot. Worst case scenario is I get an interesting race report out of it.