You already know how important it is to consume carbohydrates during a marathon.
Running at a fast pace plows through your carbohydrate resources, and if you run out, you’ll be forced to slow down substantially.
Marathoners call this “hitting The Wall.” Even though The Wall doesn’t occur until about 22 miles into a marathon for most runners, there’s solid evidence that refueling during a half-marathon is a good idea too—as your carbohydrate reserves dwindle, your brain gradually slows your running pace in an attempt to last longer before completely running out of fuel.1
But what about all those people who bring along fuel belts for a 10k or even a 5k? How short is too short to bother with refueling during a race?
What Races Require Fueling During the Run?
There are an enormous amount of scientific studies on taking carbohydrates during or right before a race, time trial, or run to exhaustion.
What we need to do is home in on the ones which straddle the divide between “too short to bother” and “long enough to take in some carbs.”
Starting on the short end, a 1981 study by Bonen et al. tested the effects of carbohydrates taken before or during stationary bike ride to exhaustion that lasted an average of 26 minutes.2 Though ingesting carbs had some effects on blood glucose levels, the subjects who consumed carbs either before or during the ride to exhaustion performed no better than the subjects who didn’t take any carbs at all.
A 2000 study by J.B. Mitchell and colleagues at Texas Christian University investigated whether fueling up with carbohydrates an hour before a treadmill 10k would have an effect on performance in moderately-trained runners.3 Again, the carbohydrates had no impact on race times. The finish times for the carbohydrate-fueled runners and the water-only runners was virtually the same: just a bit under 42 minutes for both groups.
Moving up to longer exercise durations, a 1995 study in the International Journal of Sports Medicine followed cyclists who ingested either a sports drink or an artificially sweetened placebo drink during a 60 minute hard ride on a stationary bike.4 This time, the data showed that the carb-fueled cyclists were better able to maintain their power output throughout ride. More specifically, power output between 40 minutes and 60 minutes was substantially higher in the carbohydrate group—they didn’t slow nearly as much as the riders who used the sugar-free drink.
Once we start looking at studies on 60 minutes or more of hard exercise, the advantages of carbohydrates are clear.5
The narrative of the scientific research indicates that 40-45 minutes is a fairly strong breaking point for how far is far enough to justify taking some carbs, either before the race or during.
According to a 2011 review by Louise Burke and other researchers, the advantages of carbohydrate refueling in a race between 40 and 75 minutes are mostly the result of the carbohydrates stimulating the central nervous system, not actually from increases in your body’s carbohydrate reserves.1
Here’s the deal:
Because your brain senses that you’ve got carbohydrates coming into your body, it decides that you aren’t in any danger of hitting the wall, so it lets you push yourself a little bit harder. This is convenient, since it means you don’t need to target any specific amount of carbohydrate ingestion—just a few sips of a sports drink will do the trick.
Conclusion
Getting back to our initial question, a 5k is definitely too short to bother with carbs, either before or during the race.
For a 10k, it will depend on how fast you are. Speedy runners who expect to cover the distance in under 40 minutes don’t need to worry about carbs at all, but if you typically run between 45-60 minutes in a 10k race, you might consider taking a swig of sports drink before or during the race.
The benefits of fueling don’t really kick in until you get to a 60-75 minute race, though, so don’t feel compelled to wear a fuel belt or make a dash for the aid station in anything shorter than an hour if you don’t want to.
What Fuel is Best?
Now you know what the cutoff is for deciding whether to have fuel or not, but deciding which to use can be an overwhelming decision. We have already informed you thata fuel source with protein can increase your risk of GI stress, but ultimately, your fueling decision comes down to finding out what works for you.
We know that is not what you wanted to hear, and we wish we could give you one product that rules the others, but unfortunately it comes down to practice, and what your body tolerates the most.
Here’s the deal:
Carbohydrates are stored in both the muscles and the liver. Your performance on race day relies on using the glycogen stored in the muscle. For glycogen to make its way to the muscles, it must first be digested, make it’s way through the intestinal wall, and then absorbed by the muscles. This process takes time and isn’t very efficient.
However, gels will often “wake you up” in a very noticeable way because our brain only runs on the glucose stored in the liver. As the muscles start to absorb more blood glucose, the brain gets less glucose and starts to get hazy (you’ve probably noticed this feeling on your long runs or if you ran without eating enough).
Often, a gel will wake you up and help the mind feel energized, but it doesn’t necessarily help you physically.
When running hard, your body often diverts blood away from the digestive track to help give your legs more blood (and therefore oxygen). Sometimes, your body shuts the stomach down completely while other times it just slows down.
This is why it isn’t uncommon to see runners throw up fluids or gels right after ingesting them late into the race.
Therefore, you want to begin taking gels relatively early into the race. By taking the gels early, your body shouldn’t be under great duress and you have a better chance of processing the sugars faster and without stomach issues.
Any specific brand recommendations?
Our post on Which Energy Gel is the Best providedthe ingredients list of some popular gels, in addition to an explanation to what those ingredients are, and what the pros and cons are of each.
This should help your decision making process a little, and if you are considering Sports Drinks or Gummies, they are compared in another previous article.
What’s the bottom line?
The key to finding the perfect gel is testing, trying, and sampling a wide variety of flavors. Using this ingredients list, pick your favorite and give a few a try. Find the taste you like best and make sure to practice on your training runsbefore making fuelinga part of your race strategy.
If you need more information on fueling, or if you have a marathon coming up, check out ourMarathon Nutrition Blueprint: A Guaranteed Formula to Never Bonk During the Marathon Again. You won’t regret it!
