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How This Dietitian Preps For Endurance Races

It was during my first 50-kilometer trail race in the Michigan wilderness that I became enamored with endurance races. A week after the pain of that accomplishment subsided, I signed up for (and eventually completed) my first 50-mile race, which took place on the grueling mountain trails of San Diego.

Throughout the past eight years, I’ve participated in endurance races with distances up to 100 kilometers—and I’ve tried just about every diet and supplement regimen out there in attempts to improve my performance and recovery. The one thing that remains true: The longer the race, the more vital it is to have a proper nutrition and hydration plan.

While I still occasionally catch myself making the same rookie mistakes I did on day one, here are some key nutrition pointers that have helped me over the years.

1. Know Your Hydration Needs

I can’t express the importance of this enough, but hydration is crucial when it comes to endurance competitions. A body weight loss of even two percent from sweat can negatively impact performance. I’m someone who sweats a lot (I’ve recorded up to a six percent sweat loss in just a few hours) so you can imagine how crippling under-hydration can be during longer endurance races. I’ve had to cut both training sessions and races short when the losses became too significant.

How do you avoid this? The majority of endurance athletes sweat between two to 10.5 cups per hour. Since this is a pretty big range, I recommend assessing your sweat rate.

Sweat rates vary based on several factors, including but not limited to: weight, temperature, humidity, type of exercise, exercise intensity, clothing, and being in a fasted or fed state. For example, my sweat rate during a 70-degree, moderately-intense run is around 54 ounces per hour. In order to support peak performance in this scenario, I need to drink almost seven cups of fluid per hour.

You can calculate your sweat rate by weighing yourself before and after activity, adding the change in body weight to the volume of fluid consumed during activity, and then dividing that total volume with the exercise time. From there, you can figure out how much fluid you need to drink per hour of exercise.

For an easy calculation, try my quick sweat rate calculator:

  1. Body weight (in kg) pre-exercise: ______kg
  2. Body weight (in kg) post exercise: ______kg
  3. Change in body weight (A minus B): ______kg
  4. Convert kg to grams (C x 1000): _______g
  5. Volume of fluid consumed during activity: ______oz
  6. Convert oz to mL (E x 30): ______mL
  7. Find sweat loss (D + F): ______mL
  8. Exercise time: ______minutes or hours
  9. Find sweat rate (G divided by H): _______mL/min or mL/hour
  10. Find sweat rate in ounces (Multiply I x 30): _______oz/min or oz/hour

2. Recharge with Electrolytes

In addition to water, we also lose electrolytes through sweat. The main electrolyte lost in sweat is sodium, and losses vary between 30 milligrams to 500 milligrams per cup of sweat lost. Other vital electrolytes lost in sweat are chloride, potassium, magnesium, and calcium.

Electrolyte formulas vary, so it’s best to test different options to see which ratios make you feel best. An electrolyte powder providing 200 milligrams of sodium per cup serving will only work for the athlete who loses 200 milligrams of sodium per cup of sweat. Through much experimentation, I’ve found that I feel best near a three-to-one ratio of sodium-to-potassium (though you may prefer two-to-one).

Once you have your sweat rate figured out, you can figure out your electrolyte needs. I suggest starting with 100 to 200 milligrams of sodium—and a third as much potassium—per eight ounces of water. From there, experiment with different ratios and concentrations to find what works best for you. One thing to keep in mind: Your diet and other fuel impact the best electrolyte ratio for you. If you use a carb product like Honey Stinger Organic Energy Chews during your race, for example, take into account the sodium and potassium it provides when calculating how much electrolytes to add to your water.

3. Fuel Up or Fast

Our quickest energy source is carbohydrates, so the majority of endurance athletes use a carbohydrate-fueling method. In seasons when I used carbohydrates as fuel, I consume a well-balanced yet carb-focused meal about two hours before training.

After my first hour, I take BCAAs and glutamine. (I use True Athlete Grape Endurance and Recovery and True Athlete Glutamine Sport.)

From that point on, I also follow the ’30 to 60 grams of carbohydrate per hour of exercise’ rule. I usually start with a Honey Stinger, gel (like GU Energy Gel), or powdered carb source (like Karbolyn).

Then, after two hours, I shoot for about 200 calories per hour. After four, I start incorporating more protein to help ward off muscle breakdown. I’ll do gluten-free PB&J and a protein shake (like True Athlete Natural Whey Isolate mixed with water or a pre-made Orgain Vegan All-in-One Protein Shake), and I might even munch on some beef jerky or a tuna pack.

I recommend experimenting with different carbohydrate fuel sources to pinpoint what gives you the best energy levels without causing digestive issues.

Alternatively, some endurance athletes train their bodies to become fat-adapted by doing fasted workouts or carb-cycling. I began doing this myself once I realized my hanger and low blood sugar symptoms every couple of hours throughout the day were due to carbohydrate dependence. Training your body to use fat stores as energy can be useful later in a race when your body has depleted its glycogen (the carbs stored in your muscles).

Read More: Should You Try Carb Cycling

The notorious wall, or “bonk,” many athletes reference can be avoided (or drastically reduced) if your body can effectively flip over to using fat. In fact, I have run and successfully finished several keto ultras and marathons. My recovery was remarkable, I experienced no walls, and fueling was less of a headache. That said, I did have much slower finish times in comparison to my carbohydrate-fueled events. While this conversion can certainly improve over several seasons of adaptation, I haven’t committed to testing it out. Instead, I’ve been opting for carbohydrates and incorporating fasted workouts to improve energy in later stretches of the race.

If you notice energy swings, hanger, and signs of low blood pressure, experimenting with carb-cycling and becoming more fat-adapted may do your performance a solid.

4. Recover Smart

In a carbohydrate-fueled system, carbohydrates are needed post-workout to replenish your body’s glycogen stores. Two popular post-workout carbohydrate calculations are half your weight in grams of carbohydrates or 0.75 grams of carbohydrates per pound of body weight. For example, a 150 pound person would consume 75 to 113 grams of carbohydrates

Depending on the duration of exercise, I use both of these formulas. The longer the race, the higher the proportion of carbs I include.

Protein is also essential post-workout to rebuild and repair your muscles. I usually shoot for around one gram of protein per three-to-five grams of carbohydrates—and I try to consume everything within one hour of exercise.

Plus, when sessions are longer than one hour and/or are more intense, I incorporate BCAAs, glutamine, and EAAs into my post-training supplement regimen.

5. Cut Down on External Stressors

During a 100-kilometer season in my early 20s, I began experiencing night sweats, steady weight gain, and poor recovery. I’ve learned a lot about my body since that season, and I am happy to say that those symptoms never chronically reappeared once I addressed the root cause: stress.

While exercise provides a plethora of health benefits, it is still considered a stress. Our bodies are fairly resilient to stress, but as training volume increases, it becomes imperative to be mindful of other potential triggers in order to maintain balance.

When overall stress levels become unmanaged, hormones, sleep, performance, and recovery can suffer. I find that in order to maintain balance, I must be increasingly mindful of processed foods, added sugar, alcohol, adequate sleep, and external stressors (like big projects or long work hours) leading up to race day.

My best advice: Listen to your body, consume whole foods, and consider supplementation if needed. My supplement go-to’s include turmeric, omega-3 fatty acids, tart cherry, bromelain, and glucosamine chondroitin with MSM. When I notice my overall stress levels increasing, I add one or more supportive adaptogens like ashwagandha, maca root, holy basil, rhodiola, or schisandra.

If you’re a The Vitamin Shoppe Healthy Awards member and endurance athlete, consider signing up for a complimentary nutrition consultation with one of our qualified nutritionists. We can assess your training, race day, and recovery needs to help you fuel (and perform!) optimally.

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