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How to Pace & Fuel a Marathon

Stick to your goal pace from mile 1 and beware of goal inflation. Know your maximum and minimum sustainable pace—there should only be about a 10-15 second differential. Resist the urge to go out too fast to put time “in the bank”. That will come back to bite you in the late miles, it always does! It’s way too easy to take a marathon out too fast, especially in big city marathons that may require you to “surge” around other runners at the start. Be patient and trust your fitness. The marathon distance demands respect.

The first half of your marathon should feel like you’re in control. Run steady, smooth, and focus on your fueling (more on that later). Ignore those around you who may be over pacing the early miles. There’s a good chance they will come back to you. Go through a mental checklist periodically to make sure your shoulders are relaxed, your body is upright to help maintain good running style throughout the race. I suggest writing down your target 5k splits on your forearm with a Sharpie so you can keep those splits "tight" from the start. You should go through the half marathon marker within 60 seconds of your goal if you have paced well.

Mile 16-20 is where the real race begins. You’re going to start to feel the fatigue and this is when the distance and pace starts to take a toll on the legs. It’s likely nothing you haven’t run before in terms of distance, but the intensity is going to amplify your fatigue. Use your momentum and keep your cadence in check. This is where your mental discipline of training will help you maintain your effort and positive attitude. Do your best to stick to your paces during this stage and keep the sugar coming in as it will help you focus.

Remember, during your race you’re going to experience emotional highs and lows. This is totally normal. Endure the valleys, and control the emotional highs. If at any point you are in a pretty bad “valley”, there’s a good chance you need calories.

At mile 20, you are going to need to dig deeper than ever before. The final 10k of a marathon is the most rewarding and most challenging. Until now, your race required patience to hold back. During these final 6 miles, you get to dig deep, callus your mind and use any energy that you have left. This is the stretch that a well-prepared marathoner like yourself should relish. As the finish line nears, continue to hit every aid station and gradually increase your effort. Keeping your blood sugar stable will keep you alert so that you can focus well to the end. Be smart with your effort and don’t overreach. Overreaching at this point can lead to a serious cramp and a painful last couple of miles. Enjoy the fruits of your labor and have fun out there.

FUELING: How much do you store?

Carbs are sugars (and starches) that fuel the body as gasoline fuels a car. Just like a car stores fuel in the tank, the body stores carbs as glycogen in both our muscles and liver. These reserves are relied upon to stabilize blood sugar and allow for optimal muscle function/performance.

Athletes who meet their daily needs of carbs and consume meals consisting of 50-60% carbs can expect to store about 2 grams of glycogen per pound of muscle tissue. Additionally, athletes can store roughly 100 grams of carbs in the liver.

This means that when your glycogen stores are properly topped off, you should be able to run about 2 hours at a moderate intensity without “bonking”. Obviously, this never really happens as athletes rarely function on a “full tank”, so be sure to fuel properly during exercise.

Remember, you are not just fueling today’s training session. If you finish a session on an “empty tank”, you are compromising the next training session--even if that next session is tomorrow.

FUELING: How much do you need?

When training or racing beyond 45 to 90 minutes, aim for approximately 1 gram of carb per 1 kilogram of your body weight. For example, a 70kg athlete should aim for roughly 70 grams of carbohydrate each hour of training or racing. This value is quite high and you will absolutely need to “train your gut” to tolerate this amount of fuel.

The human body can handle a maximum of 90 grams of carbohydrates per hour. Of those 90, only 60 grams can be from glucose with the remaining 30 being from another source--typically fructose.

Choose products with an ingredient list that includes multiple types of carbohydrates. Common carbohydrate sources used in sports nutrition products include maltodextrin, glucose, dextrose, sucrose and fructose. Common products used on race day include sports drinks, energy gels, energy bars and energy chews.

THE MATH: How much do you need?


1 gram of carbohydrate per kg of body weight

EX: 70kg athlete should target 70 grams of carbs per hour of effort


Your body weight (in kg) in fluid ounces

Example: a 70kg athlete should aim for 70 ounces of fluid per hour of effort


For runs over 60-70’: One PowerGel every 35-40’ or a few PowerGel Shots every 20’


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