Ultra Running

Eight Concepts for Fueling Long Runs

fueling long run

Many runners struggle with their fueling on long runs. The problem is, there are a lot of different products out there and everyone is different regarding how they handle certain foods. In this article by Ian Torrence, learn what you need to keep in mind when formulating a fueling plan. His eight simple concepts with help guide you to your best fueling choice…

Fueling right for the long haul is a vital component to a winning strategy.  However, whether the race is 10 miles or 100 miles, developing a nutrition plan isn’t a simple process.  Our best “recipe for success” will vary depending on the products we use, our individual needs, race distance, and conditions. Fine-tune your nutritional game plan and eliminate the guesswork with these basic concepts.

Concept One:  Glucose is an efficient fuel source for endurance athletes.

Glucose is the most basic form of carbohydrate or sugar.  It is also our body’s “go to” source for energy during moderate and fast running.  Glucose is stored as glycogen in our muscles and liver and the trained athlete can store enough glycogen to provide energy for roughly two hours of moderately intense activity like marathon racing.  It’s no surprise then that many runners begin to hit the “wall” at around two hours into their marathons.  One part of avoiding these extreme energy lows during races is to replace sugars during the race to spare your limited glycogen stores, thus the need for a proven nutritional plan.

Concept Two: Intensity determines fuel usage.

Our body utilizes stored fat for low intensity activities like easy running.  However, the body does need to use a small amount of sugar to begin this fat burning process.  If you completely deplete yourself of carbohydrates you’ll make this fat utilization process extremely difficult and running will be next to impossible. If you’ve ever hit the wall, then you know what I mean.

As your effort and pace increases, the body relies more and more on glycogen as the primary energy source.  Obviously intensity levels vary for every runner depending on the race distance but in long races, there is a fine line between pace and glycogen usage. Run too fast for too long and you’ll deplete your glycogen stores before the finish line.

Concept Three: Race success relies on preventing a drop in blood glucose as well as depletion of muscle and liver glycogen.

To maintain adequate blood sugar levels and avoid an early depletion of your muscle and liver glycogen stores, you can manipulate several key elements during the months before your race as well as on race day.

In Training:

Runners who are more efficient at burning fat at race pace will spare their limited glycogen stores. There are two strategies for increasing your fat burning on selected easy and long runs.  One is for athletes who are new to running to train on low carbohydrate stores. The second is for runners who have experience with “training low” – running in a carbohydrate depleted state.  Runners may want to select a few long runs and easy runs within their training program to try these strategies. Note that I said, “Select a few long runs and easy runs.” This is not a strategy for every easy run and long run but something you can do a few times across your training plan to boost your ability to burn more fat at race pace.

Carbo-Depleting Newbies

(little to no experience with carbohydrate depleting runs)

Before Workout: Begin the workout after a night’s sleep and eating no breakfast. If you run in the evenings, fuel with very little carbohydrate throughout the day and before the run.

During Workout: Water and electrolytes are okay. No carbohydrates for runs under 90 minutes. If your run exceeds 90 minutes, use 20-40 grams of carbohydrate per hour starting at the beginning of the run.

After Workout: Refuel immediately adhering to the principles in our RUNRR article.

Advanced “Depleters”

(have experience with carbohydrate depleting runs in several previous training cycles)

Before Workout: Do a post-dinner run the night before. Begin workout after a night’s sleep and no breakfast. You can also run twice a day and refuel with very little carbohydrate between the first and second session.

During Workout: Water and electrolytes are okay. No fuel for runs under 2 to 2.5 hours.

If your run exceeds this then use 20-40 grams per hour from the beginning of the run.

After Workout: Refuel immediately adhering to the principles in our RUNRR article.

The bottom line here is that if you are new to running on low carbohydrate stores, do some runs that last up to 90 minutes without any carbohydrates before or during. If you are more experienced at “training low” then stretch the no carb runs to 2-2.5 hours. If you run longer, then don’t fuel before but do begin fueling at the start of the runs.

In Your Race:

Now that you can burn more fat and spare your carbohydrate stores at race pace from using the advice above, you’ll want to fuel appropriately during the race so you can race your fastest.

Before Race: Begin the event well fueled with your carbohydrate stores topped off.

During Race: Most runners do not fuel adequately during goal races.  Consume 30-60 grams per hour depending on distance and intensity of the event. Note: The typical energy gel contains roughly 20 grams of carbohydrate.  Optimal fueling requires some trial and error in training to find the products and timing that works for your body (see Concept Four below).

After Race: Refuel immediately.  RUNRR

Concept Four: Eating and drinking will see you through to the end.

Hopefully, you are now convinced that you need a robust nutrition strategy to run your best.  The next question, of course, is how to choose a carbohydrate source. After all, carbohydrates (sugars) are the best fuel for intense endurance events.  Note:  Ultramarathons may require additional dietary fats and proteins due to widely fluctuating efforts and duration.

It’s important to realize that not all sugars are created equally.  There are high, moderate, and low glycemic sugars.  The glycemic index indicates how quickly the sugars raise blood glucose levels. Below is a chart of several common sugars that you will find in sports nutrition products.

Glycemic  indexes for common sugars Scale: 0-100 where 100 raises blood glucose levels fastest
glucose ~99
maltodextrin ~85
high fructose corn syrup ~78
sucrose ~68
agave nectar, raw honey ~30
brown rice syrup ~25
fructose ~20

Here’s what athletes find: Slow burning fuels (low glycemic index) are not optimal for high intensity and long duration endurance events.  They perpetuate “the bonk” because they are slow to digest, cause the body to utilize and rely on stored glycogen, and create gastric distress because they linger in the digestive tract.

Fast burning fuels, those with high glycemic indexes, will keep blood glucose levels high, thus reducing the need for the body to tap into stored muscle and liver glycogen.

Start with products that contain high glycemic sugars and see how your body reacts. Experimentation over a few long runs and tune up races will help you dial in exactly what works for you.

And remember, a body in motion works differently than a body at rest.  Therefore, the fuels you ingest will also be put to work differently.  Some products that work well during easy runs may not work as well at race pace so the mantra “practice makes perfect” applies. Try your chosen fuel at different intensities and durations to make sure it will work on race day.

Concept Five: You must pace yourself realistically.

Linked closely with nutrition is pacing. When it comes to racing long races, too many runners feel that “putting time in the bank” – running faster than goal pace in the early going – is a good idea. Wrong. Banking time is a very bad strategy for long races. Running even splits or at a consistent effort is the best approach because erratic pacing or running too fast too early will use up your glycogen very quickly.

To find a realistic race pace, we advise that you use shorter events throughout your training plan to test your fitness then plug your race results into the McMillan Running Calculator. Check out the Race Times tab to estimate a sensible race time for your goal race.  And of course, be prepared to modify your pacing plan depending on race day conditions.

Concept Six: Tonicity or why you feel ill late in the race.

Do not neglect the concept of tonicity, the measure of the amount of substance dissolved in a liquid.  The optimal fueling ratio is a 6-8% carbohydrate solution (4-8 grams carbs/100ml or ~3.5 oz of water).  This hypotonic mix empties from the stomach quickly and is absorbed by the intestines easily, which is why it is the ratio for most sports drinks.

However, what was once a hypotonic solution can quickly become a hypertonic solution as you dehydrate and lose electrolytes during a long run or race. This is why many runners find that the drink they used early in the race becomes intolerable later in the race.

Hypertonic solutions contain a higher concentration of electrolytes and/or carbohydrates than the body and are not as easily digested.  They pull water from the body and cause cramping, discomfort, and nausea.  As you get deep into the race, you may need to dilute your fuel to match the growing dehydration that is inevitable in long competitions.

Concept Seven: Adjusting nutrition for weather

You’ll also need to account for weather conditions in your nutrition strategy as it affects your fluid’s tonicity relative to your body and, in turn, your fueling rates. The warmer the temperatures, the more water you’ll need for proper calorie absorption. Here’s a quick guide to hydrating in varying conditions.

Weather conditions Suggested fueling rate
Warm to Hot temperatures 100 calories/12oz of fluid
Cool to Cold temperatures 100 calories/6oz of fluid

It’s important to note that athletes have individual heat tolerances.  What’s considered hot for a runner who’s trained in Minnesota all winter will not be the same for a runner who has done the same training in Phoenix, Arizona.

I should also note that electrolyte use and hydration rate will vary depending on an individual runner’s sweat rate, fitness level, daily sodium consumption, and weather.   Take a sweat rate test (search the Internet to find the protocol) to determine how much fluid you’re losing under different weather conditions and efforts. While running at high intensities begin the hydration process before you feel thirsty.  When working hard in hot conditions, ingest 400-800 mg of sodium/25-32 ounces of water/hour.  If necessary, use electrolyte pills or tablets to reach those levels.

Concept Eight: Sip and carry.  Don’t grab and gulp.

We highly recommend that you carry all the fuel you’ll need on race day or make sure you can re-supply along the course (either at race-provided water stops or from your crew in ultra races).  Wear a hydration system and don’t rely on aid station tables to have what you need when you need it.  The weight of your equipment is negligible compared to the loss in time you’ll accrue if you run out of food and fluid.

The Finish Line

These fueling guidelines are as important as your training plan. Recognize that there are many personal differences and preferences when it comes to fueling. Experiment and find what works for you. Start with these proven guidelines then modify based on your experiences. Over time, you will determine the best race day nutrition plan that helps you race your best. Good luck!

McMillan Coach Ian Torrence is a legend in the ultra & trail running community. He’s completed 180 ultramarathons, winning a staggering 52 of them.  He suffered through every available nutrition strategy to come up with these guidelines.

 Source: McMillan Running

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