Let’s address the elephant in in most marathon training plans.
That mythical 18–20 mile long run.
The one that ruins your Sunday, wrecks your legs, and makes you question every life choice around mile 16.
Here’s the honest question more runners are quietly asking now: Do you really need it?
I’ve met runners who swore by the classic 20-miler—and others who got injured every single time they touched that distance.
I’ve skipped them myself in certain cycles, leaned into alternatives, and learned the hard way where that gamble pays off… and where it bites you.
This isn’t a “long runs are useless” hot take. It’s a reality check.
Because yes—you can finish a marathon without those monster runs.
But whether you should depends on your goals, your body, your schedule, and how smart the rest of your training is.
Let’s break this down honestly: what you gain, what you risk, and how to replace the classic long run without lying to yourself about the trade-offs.
What Happens If You Skip the Classic 18–20 Mile Long Runs?
So, what happens if you train for a marathon without doing those legendary weekend 18- to 20-milers?
Let’s break it down — the good, the bad, and the brutally honest.
The Upsides
You’re Less Likely to Get Wrecked
Long runs over 3 hours? They might do more harm than good.
Research (shoutout to RunnersConnect and PubMed) shows that the risk of overuse injuries like IT band flare-ups, stress fractures, and knee blowouts goes way up after that mark.
If you’ve ever hobbled around for days after a monster run, you know the deal. Keeping your long runs shorter might keep you on the road instead of the sidelines.
Better for Busy Runners
Let’s be real — most of us aren’t full-time athletes.
If you’ve got a job, a family, or just don’t want to wake up at 4:30 a.m. every Sunday, this style makes life easier.
You can fit in quality work without blocking off half your day.
That alone makes it sustainable — and if your plan isn’t realistic, you won’t stick to it.
More Recovery = More Consistency
Ever done a 20-miler and felt like garbage for three days? Yeah, same.
If you’re not constantly beat up from epic long runs, you can actually get more quality training in — midweek tempos, hill repeats, whatever. And that adds up.
Mentally Fresher
Some runners love long, solo slogs. Others? Not so much.
Switching things up with doubles, tempo efforts, or even a bike session can make training feel less like a grind. It keeps the fire alive.
Personally, I’d rather mix it up than dread my weekend run every week.
You’re Respecting Your Body’s Red Flags
If every time you go over 15 miles something starts barking — your hip, your Achilles, your hamstring — then why keep pushing that same button?
I’ve coached plenty of runners who thrive once they back off from that mileage ceiling. Sometimes staying healthy means working smarter, not harder.
The Downsides
“The Wall” Is Still Real
Without those monster long runs, you’re not building the same fat-burning engine or glycogen stores.
Bonking at mile 20 becomes more likely — especially if you don’t practice fueling properly.
Even great nutrition can’t fully cover for under-training. Be ready.
Less Time-on-Feet Prep
Marathons are about duration, not just distance.
If your longest run is 12 miles, your joints, muscles, and brain might be in for a rude surprise at mile 22.
Think: cramping quads, barking feet, mental fog.
It’s like trying to hike 8 hours when your longest was 4 — your body just doesn’t know how to handle it yet.
Confidence Might Take a Hit
There’s something powerful about knowing you’ve already run 20.
You toe the line thinking: If I did that, I can do this.
If your longest is 14 or 16, the final 10K might feel mentally shaky. That said, I’ve seen runners crush marathons off shorter runs because the rest of their training was dialed in.
Planning Gets Trickier
Non-traditional plans take more thinking.
It’s not as simple as “add 2 miles to my long run each week.”
You’ve got to balance tempo runs, back-to-back days, and cross-training.
If you wing it, you might end up doing too little — or way too much.
You Might Lose a Few Minutes
Here’s the truth: if you’re racing for a time — not just finishing — those long runs can be difference-makers.
There’s a reason elites still do them.
Will you finish without 20-milers? Probably.
Will you race your best? Maybe not.
This is similar to the topic of training for a marathon on only three runs per week – I’ve already covered it here. You can cover the whole distance, but it’s not gonna be your full potential.
I always say: You can finish a marathon without long runs — but to run it hard, you’ll want them in the mix.
Creative Ways to Simulate a Long Run
Sometimes you don’t have the time, the recovery window, or the will to bang out a 20-miler.
Here’s how to still get the job done.
Split-Day Simulation
Run in the morning, rest, then run again in the evening.
Example: 13 miles easy in the morning, then 7 more at night. That’s 20 miles total — with recovery in between.
It’s not perfect, but it hits many of the same systems, especially for fuel depletion and pacing practice.
2 Hours Easy + 30–60 Minutes at Marathon Pace
This is brutal. But it teaches you what the back half of a marathon feels like — trying to move well while tired.
You also get to practice pushing late without dragging out the total mileage too much.
Fast-Finish Long Run
Steady effort for most of it, then crank it up in the last few miles.
You’ll feel like quitting — which makes it perfect training for race day.
Tune-Up Races & Real-Time Practice
Instead of slogging through a solo 20, why not jump into a race?
A half marathon at 4–6 weeks out is golden. You get the crowd energy, aid stations, race-day jitters — all things you want to experience before your goal race.
Want more volume? Add miles before or after.
I’ve had runners jog a few miles as a warm-up, race 13.1, then cool down for 3–5 more.
That adds up to 18+ miles with a nice confidence boost baked in.
The Interval Long Run Hack
This one’s funky, but hear me out: break your long run into chunks with short rests.
Run 5 miles, rest 5 minutes, hydrate, stretch, repeat.
Keep doing that until you hit your target distance — maybe 18 miles or so.
It’s not about slacking. It’s about form preservation and reducing breakdown.
You still get endurance benefits but avoid the ugly form-collapse zone that hits many runners after hour three.
Especially helpful for newer runners or those worried about injury risk.
Why It Works
Marathon day isn’t just about running long. It’s about problem-solving: managing pace, fueling, gear, and mindset when everything gets hard.
These simulations give you reps. You test out shoes, gels, pacing plans. You learn what works before you hit the wall.
And when you survive one of these workouts? Your brain remembers — and starts to believe you can do it.
Real Talk: Pros & Cons
Pros:
- Builds confidence without overcooking your legs
- Simulates race conditions — gear, pacing, fueling
- Crowd energy during races can lift your performance
- Less mental burnout vs. a solo 20-mile sufferfest
- Helps break the fear of the unknown
Cons:
- Nothing quite replaces a single long run’s grind
- Easy to turn simulations into accidental races — and overdo it
- Double runs = more prep, more laundry, more logistics
- May not save much time in the end
- Some runners hate splitting it up — mentally they prefer one-and-done