There’s a quiet trade most marathoners make without noticing.
They (and when I say they… I also mean the collective and royal “we”), protect the long run at all costs and stop racing entirely for 16, 26… 52 weeks. They call it “staying focused.” I called it that too, for the first half of my running life because I deep down don’t love racing (it ruins my training schedule and the logistics around races drives my obsessive compulsive brain insane… I digress).
I realized, though, that it’s actually the thing keeping a lot of us stuck at the same marathon time, year after year.
The 5K is where suffering actually lives. The last 5-10 minutes are usually a “my legs are on fire and I want to lay down on the side of this road” kind of energy. Same exact internal conversation you’ll have at kilometer 32 (20 miles) of your marathon when the wheels come off… but a smaller time frame.
Matt Fitzgerald (running coach, author of 30+ amazing running books, etc.) backs this up. He says marathoners should be doing as much Vo2 Max speed and tempo work as 5K runners, especially in those first 6-10 weeks of the marathon build period. That’s what raises your aerobic ceiling and that’s what makes marathon pace feel like cruising instead of grinding.
How the 5K is the real cheat code for the marathon
And then there’s the part that flips this from “fine, race a 5K” to actual cheat code:A 5K isn’t just a workout. If you actually let it, it becomes a full marathon dress rehearsal compressed into 15-30 minutes.
You get to practice:
- the nerves
- the morning fueling/hydration
- the warmup.
- the shoe choice
- the “do I take a gel or not 20 minutes before the gun start” question.
- the pacing math.
- the mental game when it hurts.
And so much more!
You get to mess all of it up at low stakes:
- Wrong breakfast? You lose 20 seconds, not your sub-3 hour goal.
- Forgot anti-chafe stuff? Lesson learned, cuz it costs nothing.
- Tried a new caffeine gel and felt sick at kilometer 4 (2.5 miles)? Now you know not to do that in November on the real course.
You can’t practice running 42.2km (26.2 miles) on a long run but you can practice the race day of a marathon by doing a proper 5k.
I also believed the myth that a 5K will destroy 4-5 weeks of marathon training. FALSE.
If you’re fit and have some base built up, the recipe is dead simple:
- 3 day before easy. Like, actually easy and no hero workouts (I also wouldn’t lift weights in those 3 days as we don’t need the fatigue)
- Go and suffer in the 5K (yes really, fully empty the tank, that’s the whole point).
- 3 days later do a shake-out easy 30 minute run some mobility, nutrition/hydrate up and get good sleep.
- By day 7 you’re back to marathon work like nothing happened.
One-week dip in volume for a massive bump in fitness, race practice, and toughness. The math IS actually mathing here.
I paced a guy that I coach and talk about a lot in here, Brenton, through his second ever 5K this past weekend (Ironically he’s done 10-15 marathons though, ha!).
Eight weeks ago he thought 5Ks were a waste of time but this weekend he ran 18:29 nearly 30 seconds faster than his lifetime best. And… he’s not even training for 5Ks.
The full episode has Brenton’s actual race footage, me pacing him, the start line conversation about pacing, and why this is the cheat code for sub-3 marathoners.
Watch it or listen on your next workout to it here.
