Why is My Longest Marathon Training Run Only 20 Miles?

What Should Your Longest Training Mileage Be for the Marathon?

Runner Runs Past Washington Monument
Alex Wong

Question: Why is My Longest Marathon Training Run Only 20 Miles?

"I'm training for my first marathon, and I was surprised to see on my training schedule that my longest training run is only 20 miles. Shouldn't I be running longer during training, in order to be ready to run 26.2 miles?"

Answer: 20 Miles is Enough and Not Too Much for Marathon Training Distance

Many first-time marathoners wonder why so many marathon training schedules don't go beyond 20 miles.

How can you be prepared -- both mentally and physically -- to run six miles beyond your longest run?

There is a lot of debate about this issue. But most running experts will tell recreational marathoners that it's not a good idea to run more than 20 miles at one time during training. The reason is that running more than 20 miles takes a toll on your body. You'll need a long recovery period, and you run a high risk of getting injured.

Running 18 to 20 miles as your longest training run will prepare you to complete the marathon. So, the potential negative effects of running longer than 20 miles outweigh any possible benefits, such as feeling more mentally ready to run 26.2 miles.

The Effects of Long, Slow Distance Training

Also, it's important to remember that being prepared for your marathon is not about just one long run -- it's about the consistent training you've been doing for months. If you've been following your marathon training schedule, you'll be ready.

The training schedule is built to increase steadily the distance of your longest run. Most schedules aim at increasing it no more than 10% per week. This is a rule of thumb for athletic training to consolidate the fitness gains without increasing the risk of injury. You add a little more stress to your muscles, aerobic metabolic system, and mental toughness.

But the stress is only enough that you are fully recovered in a week for your next long, slow distance run.

With your long training runs, you are building calluses on your feet so they will be less likely to blister. You learn where you chafe and what to use to prevent it. You learn how to hydrate right and when to take on energy snacks. You also develop the mental toughness and confidence to get through hours of running.

Tapering Two Weeks Before the Marathon

During the two weeks before your marathon, you'll be cutting back your mileage. This tapering period will allow your body to recover from all those months of training. You'll feel rested and ready to take on the 26.2-mile distance.

But What About that Final 6.2 Miles?

Race day is going to be different from a training day. It's exciting, maybe even a little terrifying. You'll have the other runners to compete with and people cheering you on during the final miles. When you pass "the wall" after 20 miles, you'll be focused on the finish line.

It's only a 10K with a 20-mile warm-up! By tapering to allow your body to be in top, uninjured condition, you will make it across in style.


Bosquet, Laurent; Monpetit, Jonathan; Arvisais, Denis; Mujika, Inigo: "Effects of Tapering on Performance: A Meta-Analysis. Medicine & Science in Sports & Exercise. 39(8):1358-1365, August 2007.

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