Is three runs a week enough for marathon training?

The dream of the three-run week

On paper, three runs a week sounds ideal. You get balance. Rest days. Time for a life. You read about elites who only run “quality sessions” and think, well, I’m basically doing that, just slower and with more snacks.

It’s the minimalist’s approach to marathon training: one interval session, one tempo, one long run — simple, efficient, elegant. The problem is, marathons aren’t elegant. They’re long, messy tests of fatigue resistance, and you can’t fake endurance with structure alone.

Where the three-run plan came from

The idea exploded after the FIRST (Furman Institute of Running and Scientific Training) program made it popular in the mid-2000s. Their “Run Less, Run Faster” philosophy claimed you could achieve marathon fitness with three focused runs a week, plus cross-training on the other days.

The science wasn’t nonsense. Three quality runs can absolutely build cardiovascular fitness, raise your lactate threshold and sharpen running economy. The issue is the asterisk nobody reads: the plan only works if you actually do the cross-training — cycling, swimming, rowing — at a decent intensity.

The physiology behind why it (sometimes) works

Each of those three sessions targets a different system:

• Speed or intervals improve VO₂ max — the amount of oxygen your body can use during intense effort.
• Tempo or threshold runs train your body to clear lactate more efficiently, delaying fatigue.
• Long runs build aerobic capacity and teach your muscles to store and use glycogen more effectively.

When you hit all three consistently and recover properly, you’re still training most of what matters for marathon performance. The missing piece is volume — total time spent running. Endurance adaptations (more mitochondria, stronger slow-twitch fibres, improved capillary density) depend heavily on total mileage. Three days a week can hit the basics, but it won’t max out your aerobic development.

What it’s like to train for a marathon on three runs a week

I followed a three-run-per-week plan for the NYC Marathon 2025. The logic was sound: balance strength training, protect against injury, avoid burnout. For the first half of the block, it worked beautifully. I was always rested for my long runs, hit my intervals like I had something to prove, and convinced myself I’d cracked the code to marathon training.

Every week, I felt sharper. My interval splits looked heroic, and my Runna plan gleefully upgraded my target from sub-4 to sub-3:30. My ego grew with every kilometre.

What I failed to notice was that as the sessions intensified, my “balance” quietly turned into avoidance. I dropped the ball on cross-training. The cycling, the strength work, the recovery routines — all the things that were supposed to make three runs a week enough, slowly disappeared.

By race day, I was fit, strong, and mentally ready. But my body hadn’t built the deep endurance, the cumulative fatigue resistance, that only comes from more consistent aerobic load. My nervous system simply wasn’t conditioned to keep firing once the miles stacked up. The result: cramps, everywhere. My quads, calves, even the inner thighs joined the mutiny.

It wasn’t that three runs a week “didn’t work.” It worked brilliantly until it didn’t. The structure gave me confidence, but not durability. Physically and mentally, I was ready to run a marathon; neurologically, I’d only trained for a very long tempo run.

When does three runs a week work in marathon training?

Three runs a week works beautifully if you already have a strong base and a realistic goal. If you’re aiming to finish rather than fly, you can absolutely get through a marathon on three runs per week. It’s also perfect for:

• Injury-prone runners who need more recovery time.
• Busy runners balancing work, family, or, you know, sanity.

On the flip side, there’s a point where minimalism stops being efficient and starts being lazy.

Who it doesn’t work for

If you’re chasing a time goal, building toward higher mileage, or want to feel strong all the way to mile 26, three runs a week probably won’t cut it. Marathon endurance is built through accumulated fatigue — the grind of multiple aerobic efforts stacked week after week. You can’t simulate that with fewer sessions unless your cross-training is both consistent and purposeful.

If your “off days” turn into actual off days, you’re undertraining. And if you’re constantly sore or exhausted from trying to make those three runs do the work of five, you’re overtraining. Both roads end in the same place: a slow, crampy death march through the final 10K on race day.

So, is three runs a week enough?

If your definition of “enough” is finishing your marathon upright, then yes, three runs a week can be enough. If your goal is a new marathon PB and involves running efficiently and comfortably on race day, probably not.

Three runs a week gives you structure and sustainability, but at the cost of depth. For first-timers, it’s a smart way to get through the distance safely.