Race day nutrition – how many carbs do you really need?

For those of you preparing for a spring marathon, 20-milers are becoming an all too familiar part of your weekly training ritual. In the last post I talked about fuelling up in the days leading up to those long runs but it’s just as (if not more) important to rehearse race day nutrition during those long runs as well. All your training benefits can potentially vanish on race day if you haven’t taken the time and effort to ensure that you know exactly what you’re eating and drinking on marathon morning.

I’m sure you’ve heard this before but it’s worth repeating. DO NOT TRY ANYTHING NEW ON RACE DAY. Or race week for that matter. This is not the time to discover that coffee or eggs don’t sit well with you an hour before you run. Or that your training partner takes twice as many gels as you do….maybe you should try that too? In training, absolutely yes; on race day, an emphatic NO! I’ve witnessed the first-hand consequences and it’s not pretty.

I often speak to marathon and half-marathon clinics at our local Running Room store. Based on the questions I most often encounter, here are some guidelines I give with respect to fuelling up immediately before and during long runs and races that last more than 2 hours.

Breakfast before the long run

  • aim for 200-300 calories for each hour prior to exercise
  • reduce the glycemic index if you’re more than an hour away from your run
  • include protein to keep you full and to ensure slower release of glucose into your bloodstream
  • keep it low in fibre!
  • you wake up dehydrated in the morning as your body has undergone various metabolic functions overnight. Be sure to drink 8-16 oz of water (not sports drink) when you wake up
  • sports drink is fine in the final 10-15 minutes before you begin to run (it is high glycemic)
  • generally, aim for 30-60 grams of carbohydrates for breakfast. Some suggestions: oatmeal with bananas & walnuts; sprouted or whole grain bread with almond butter; banana or apple with peanut butter; protein smoothie; eggs and fruit.    ***Experiment in training with what works for you***

It is equally important to practice what you consume during the long run. Your goal here is to maintain fluid and electrolyte levels, and to spare glycogen stores in order to prevent or at least delay fatigue. It is crucial to minimize the depletion of muscle and liver glycogen, even if you have carbo-loaded by the book. Fully packed carbohydrate stores in your body will last only for about 2 hours.

The sooner you begin topping up your tank, the less likely you will be to test the limits of your “wall”.

Fuelling tips during the long run

  • under “normal” conditions, the average runner needs 16-32 fluid ounces per hour of exercise. For best absorption, drink 1/2-1 cup of fluid every 15-20 minutes. You will require more on very hot or humid days.
  • for every pound you lose on a run, 2 cups of water are required to replace.
  • 1 pound of sweat = loss of 500 mg sodium (the equivalent of 1/4 tsp of salt)
  • dehydration will increase body temperature, reduce blood volume and thereby weaken muscular endurance and strength. Result —-> you slow down
  • your gel or sports drink should include electrolytes; studies show that ingesting electrolytes (remember: sodium, magnesium, calcium, potassium) during the run will improve performance and help delay fatigue. Electrolytes are important for muscular contraction and for optimal absorption & retention of fluids
  • **how much do you need?** Carb intake during prolonged exercise should be approximately .5-1.0 grams per kilogram of body weight per hour. A 165 lb (or 75 kg) athlete would therefore need 37.5-75 gms per hour. That is equivalent to 2-3 gels or 1-2 gels plus 8-20 ounces of sports drink per hour (most gels contain 20-25 gms of carbs and sports drinks contain 12-14 gms/8 oz)
  • important: each gel must be taken with 8-10 ounces of water (not sports drink) to promote absorption and avoid gastrointestinal distress

A number of athletes I’ve “coached” for nutrition initially have not believed they need that much carbohydrate intake during a run. These numbers do not come from my imagination, they come from research studies. Each of these non-believers came to me after their marathons, pleasantly surprised and rather stunned that they did not bonk.

Two final points I’d like to emphasize:

  1. Practice NOW, while you are training. If something doesn’t work, you still have several weeks to keep trying.
  2. Start taking your gel or sports drink within 20-30 minutes of beginning your run. Remember, you are trying to spare your glycogen stores, so stay topped up. Also, your rate of absorption is likely to be higher when carbs are consumed at a gradual rate rather than trying to gulp down 2 gels at once.

If all this is very different from what you’ve been doing, take the time to experiment now. Nutrition requires as much planning and practice as executing the workouts. After all those miles logged, why would you leave race day nutrition up to chance? You don’t ever have to come face to face with that wall.

Please let me know how it goes!!

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2 Responses to Race day nutrition – how many carbs do you really need?

  1. Terry Myers says:

    Wow!!! This nutrition plan was perfect for me on my 20 miler today!!! Amazing! I did a GU every 30 minutes, chased by 8 or more oz. of water, and supplemented the rest of the half hour with Gatorade.

    I carried 2 28 oz. water bottles and did 2 10 mile loops, refilling (quickly) at the start of the 2nd lap.

    I’m training for my 1st marathon which is on 4/28. I’m a 49 y/o male, 5’11″ @ 177 lbs and am in my 5th year of sprint triathlon. I raced mountain bikes 3 years before that and played competitive tennis for 7 years before mtb racing. I’ve ran a couple of half marathons at 2:06:xx and 1:59:xx.

    I kept my pace today between 10:00/mi and 10:30/mi. The last couple of miles I was pushing 11:00/mi due to right IT Band filing a formal complaint.

    Thanks again for putting together a perfect nutrition plan!

    Terry Myers
    Franklin, TN (Nashville)

    • Lucia says:

      Hi Terry,

      I’m thrilled to hear the plan worked so well for you! I hope training continues to go well for your marathon. Now go get that foam roller on your IT band! Good luck and let me know how your race goes.

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