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Fueling on the Run

By Lauren Trocchio, RD, LD, CSSD

Fueling a run: When is it important?

Most runners would answer this statement with “always!”, and athletes in general are continuously told the importance of fueling their workouts and races. But what exactly does that mean, and do the same guidelines apply to every run?

First, let’s think about fueling in two different categories: how you fuel on a daily basis (meals and snacks) and how you fuel directly before, during, or after a run. Paying attention to one without the other is like changing your oil but forgetting to fill up the gas tank – you need to address both for things to run appropriately.

Daily Fueling

When it comes to foods, there are endless ways to meet daily fueling needs, but a few general guidelines do apply:

  • Fuel (fairly) frequently. You don’t have to constantly have food in your hand, but most individuals do well by avoiding gaps of more than 3-4 hours between meals and/or snacks.
  • Spread out protein. Research indicates protein is put to its best use when consumed in fairly equal amounts (typically 20-40 grams) spread out evenly throughout the day (see #1). This seems to maximize protein’s muscle building capability and provide satiation with meals.
  • Consciously consume carbs. The bulk of research indicates carbohydrates are critical for any high intensity (anaerobic) work and a limiting factor for endurance exercise. Yes, we can train our bodies to use more fat for energy during exercise, however we won’t have that extra gear without carbs on board. That being said, there is evidence to suggest a benefit of occasionally consciously timing carbohydrate intake to create “low-carb” workouts as part of training programs. More on this later.
  • Focus on lean protein, unsaturated fats, and nutrientdense carbohydrates.

If you routinely skip meals, have meals without adequate protein, choose refined foods with minimal nutritional value, and/or avoid carbohydrates entirely, your training will suffer, and no amount of “during” workout fueling will fix it.

Fueling Directly Around a Run

We’ve talked daily fueling, so now we have to address the fueling that may occur directly around a run: the before, the during, and the after. Predominantly this sort of fueling focuses on carbohydrates and protein. Fluid and electrolytes are important as well, but for now the discussion will be on calorie-providing nutrients.

What exactly does consuming carbohydrates before or during a workout do for us? Yes, carbs give energy for working muscles, but they also provide other important functions, like helping maintaining blood sugar levels and in turn focus and concentration.

So when may pre-run carbohydrates be important?

  • The workout will be greater than roughly 75 minutes in length.
  • It’s first thing in the morning and the workout is high intensity or a key training workout.
  • The workout is less than 75 minutes but you haven’t eaten anything in the last 4-5 hours.
  • Race day!

There is evidence suggesting the occasional “train low” workout – which means training on low carbohydrate stores – may allow greater fat adaptations (or use of fat as an energy source). However, this approach is not recommended during high intensity or long workouts or on a frequent basis as it can increase risk of overtraining and potentially suppress the immune system. Rather, runners can experiment with this during low to moderate intensity workouts.

When is during-run carbohydrate important?

  • The workout will be greater than roughly 75 minutes in length.
  • The workout is less than 75 minutes but you didn’t fuel directly before the workout or eat anything in the 4-5 hours leading up to it.
  • Race day for events greater than 60-75 minutes. (Note: carbs can reach working muscles in less than an hour, but studies have shown a performance benefit just from swishing a sports drink during short races. So it seems performance enhancement may come from a central nervous system component triggered orally.)

The body has a limited supply of carbohydrates, hence the interest in tapping into almost unlimited fat stores. However, a combination of the two nutrients will always be used, just at different proportions. Therefore, carbs will always be the limiting factor, particularly in endurance events. Ever bonk in a race? Bonking is usually a result of your muscle and liver glycogen being depleted, and your body can’t even keep its blood sugar at a good level so it forces you to slow down the pace.

Finally, when is post-run nutrition (a combination of carbs and protein) important? And to narrow this down a bit more, let’s say when is post-run nutrition important within 30-60 minutes of completing a workout?

  • After any workout when completing multiple workouts in a day (eg morning run and afternoon lift).
  • After any workout as part of a race or competition training program.
  • After any high intensity or endurance workout.

If you are an active individual that hits the gym a few times per week, then your refueling timing has some flexibility. But if you are training for an event, doing high intensity or long workouts, or doing multiple workouts per day, post-workout fueling within 30-60 minutes becomes more important. Post-workout fueling allows you to a) replenish carbohydrate stores (particularly important after a taxing workout or when another workout is anticipated later in the day) and b) repair and rebuild muscle.

Looking for ways to carry it out? Stay tuned for future posts on example workout fueling!

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