Fall Marathoners Training: How to Prepare and Push Through 20-Milers

Training for a marathon is a substantial investment of time and energy, and now that you’re beyond the halfway point, you’ve put plenty of miles in the bank. You’ve established your base miles, extended your long run and potentially added in some specific pace work.

Now it’s time to face your biggest mileage and longest bouts of intensity. For this four-week block, your training will take even more dedication and personal sacrifice. It’s the time to remember your “why” and add in the most critical building blocks of your training cycle.

“This big phase of training is the most rewarding,” said Deena Kastor, Olympic bronze medalist in the marathon, based in Mammoth Lakes, Calif. “Take a pause and look at how much you’ve grown, mentally and physically.”

Here’s how to finish off weeks eight to 12 feeling strong and confident.

Your Workout Plan

As before, your weekly bread and butter is your long run. This time around, you’re headed toward the big ones: 20-milers. You’ll likely have two or three of these (with 14- or 15-milers on the weeks in between), and most plans call for the first around week nine or 10.

This is the most critical phase of your build up, which can be intimidating. “There’s a lot of emphasis on the 20-milers,” said Ms. Kastor. “It’s easy to put a lot of pressure on yourself to nail them, but remember it’s consistency that matters most.”

Keep up the other weekly runs that you began last cycle and start extending your goal pace runs. Be mindful to run your easy miles at a relaxed pace so that your body can recover from the harder ones.

“This is the time when little aches and pains can show up,” said Maor Tiyouri, an Israeli Olympic long-distance runner. “If you don’t get on top of them, they can turn into injuries.” If you’re worried about a nagging pain, take a couple of days off and see a physical therapist rather than trying to run through it.

Skill to Learn: Progression Run

If you’ve got a goal pace in mind, try a “progression run” within your long run every two or three weeks to practice challenging paces on tired legs. After warming up with about three miles of easy running, try to hit the next two about 90 seconds per mile slower than goal pace.

Then gradually aim to get closer to your race pace: For miles five to seven, run 60 seconds slower than goal pace. Run miles seven to nine 30 seconds slower than goal pace, and then from nine to 11 aim for goal pace. Finish whatever mileage you have left at an easy, relaxed pace.

Your Nutrition and Health

As you get into your higher mileage, feeding your body before, during and after runs becomes even more essential. That means focusing on carbohydrates, your main source of energy, all week long.

“Prior to running, make carbs and hydration a big priority,” said Starla Garcia, a dietitian and marathon runner based in Houston. “You also want to focus on fueling early in any runs longer than 90 minutes,” she said.

About 30 minutes into your run, start eating “runner foods” like gels, gummies, sports drinks or easily digestible, high-carb snacks like fig cookies, dried fruit or applesauce squeeze packets. “Keep taking in calories every 30 minutes or so and don’t worry about overdoing it,” said Ms. Garcia. “You want to be on the higher end of your calorie intake.”

Post-run nutrition counts, too, and should consist of a two to one ratio of carbs to protein, like a peanut butter sandwich. “If you don’t eat, you’ll have delayed soreness and will feel tired and sluggish,” Ms. Garcia said. “Try eating within an hour of finishing. If you don’t have an appetite, try to at least get down a smoothie.”

Rest is more important than ever, too. Hand off car-pooling to your partner and turn down late-night social invites. “Let other areas of your life slide right now in order to fit in rest and recovery,” said Erin Ayala, a Minnesota-based psychologist and performance consultant.

Your Mind

One thing is certain at this point in your training — the fatigue will come, both mentally and physically. What matters is how you respond, said Ms. Kastor. “Show up with the best mental version you have. That can be your biggest strength.”

While the 20-milers in this cycle are important, don’t let their value stress you. Assume one of the very long runs might not go as planned, and don’t let that get you down.

“If you start doubting your ability to complete the marathon because you have a bad long run, go back to your training log and celebrate what you’ve accomplished,” Ms. Kastor said.

On those long, challenging runs, the real work begins with your mental game, Ms. Ayala said. “You’re going to have some ‘dark and stormy’ miles,” she said. “Your body will hurt, you’re tired and your mind wants you to ease up. Be ready for that talk from your brain and visualize how you’ll respond.”

Those tougher miles are a trial run for race day, and learning to respond will make them easier to manage. “We spend a lot of time in our heads on long runs,” Ms. Ayala said. “Your negative thoughts don’t have to be truths. Acknowledge them, let them go and then continue.”

Amanda Loudin is a freelance writer covering health and science.