Carbohydrates for marathoners

How to avoid 'hitting the wall' during long runs.

If you’re a marathoner (or training to be one), you may have noticed that many popular supplements intended to improve your physical performance, fall flat when used during endurance events. Pre-workout supplements and stimulants, for example, don’t work because a marathon typically lasts longer than the stimulant itself, leaving you crashing mid race. Even Creatine, a supplement used to improve physical performance, is counterproductive because it results in temporary water weight gain, which makes running harder.

Carbohydrate supplements however, are far more effective than traditional physical performance enhancers. Gel packs, or energy gels, are ideal for improving marathon performance because they are easy to ingest during a race.

Energy gel supplementation

So what makes gel packs so effective? Runners talk about eating a big bowl of pasta the night before a race because “carb-loading” is a good way to increase glycogen levels. A lot of glycogen is used in the first 10 minutes of exercise, and the rate of glycogen use falls until it is depleted altogether.

Have you ever ‘hit the wall’ during a marathon?

Glycogen depletion is responsible for that feeling. Eating a lot of carbohydrates the night before might delay the wall, but it won’t necessarily prevent it altogether. This is why energy gels are an ideal way to get mid-race carbohydrates. They are dense and viscous, which reduces the risk of intestinal upset, even during exercise. Plus, they’re light and portable, which means you can carry them with you or easily snag a few from an aid station. Just don’t forget to properly dispose of the wrapper!

The evidence

A recent study investigated whether energy gel supplementation in the middle of a race can help delay or prevent hitting the wall during a marathon. Researchers split non-elite marathon runners into two groups. One group was provided energy gels containing 20 grams of carbohydrates and 30 milligrams of caffeine (equivalent to one cup of tea), and were told to eat two before the race, one when they believed they had hit the wall, and another every 20 minutes afterward. The runners in the second group were left to fend for themselves. Researchers also monitored the water intake of both groups.

The results show that the energy gel group was able to maintain its speed throughout the marathon, while the control group began to drop off around the halfway point. Though both groups were running at about the same speed at the beginning of the marathon, researchers found significant differences at the last three checkpoints of the race, beginning at the 18 mile mark.

The runners supplementing energy gels averaged a completion time of 3:38.31 while the control group had an average completion time of 3:49.26. Energy gel supplementation was found to improve time by just over 10 minutes, or by about 5%.

Preparing for the race

Runners having trouble with energy levels or anxious about hitting ‘the wall’ for the first time can consider energy gel supplementation to improve their time and avoid getting hit by a ton of bricks.

Never try anything for the first time during a race. If energy gels sound right for you, try taking one or two during a long training run. You don’t want to find out gels disagree with you when you’re lining up at the starting line.

New to running? Click here to check out our guide to supplementing for joint health.


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