Whether logging miles on the trail, sending a climb, or in the backcountry, your body needs fuel to support your adventurous pursuits. What you put into your body impacts your ability to maintain training intensity, duration, and overall performance. Throughout the day our body uses a combination of energy sources, whether it be fat, carbohydrates, or protein. However, when exercising at moderate or high-intensities, our body relies primarily on carbohydrates. Therefore, when training or competing, carb intake should be our main focus to provide our bodies with the energy they need so we can crush our performance goals.
Carbs equal fuel
We need to keep the gas tank full to keep the engine running. Our body can store carbohydrates in what we refer to as muscle and liver glycogen. However, just like the gas tank in your car, your body can hold only so much fuel. As activity continues, your glycogen stores begin to diminish – aka the fuel in your tank starts to get low. If these stores are not replaced, your ability to maintain intensity and work output decreases, while the rate of tissue breakdown increases. In turn, your training is compromised and a greater physiological toll is taken on the body, which not only impacts your performance in the present but also the future.
Consuming carbs during training aids in maintaining blood glucose levels and sparing glycogen. This translates into improving your ability to go longer, harder and ultimately enhances your performance. Generally speaking, carbohydrate recommendations are based on the duration and intensity of exercise. Below, we will go over common recommendations pertaining to how much, when, and what types of carbs you should be consuming to fuel your training. Keep in mind: Carb intake can depend on personal goals, training regime, GI tolerance, and many other variables. Therefore, finding the best fueling strategy for you may involve some experimenting.
Typically if your training session is less than 45 minutes, carb intake may not be necessary, unless intake was inadequate leading up to your training session (i.e. you haven’t had enough carbs throughout your day). Consuming carbs likely won’t be detrimental, however, it’s just not the focus. Instead, it’s typically recommended you focus on proper fluid and electrolyte replacement.
1 hr - 2.5 hrs of Moderate/High-Intensity:
When activity extends beyond 60 minutes at a relatively high-intensity, fuel stores begin to be challenged. In these scenarios, a carb intake of 30-60 g/hr is recommended to maintain blood glucose & glycogen levels to support training.
>2.5 hrs of Moderate/High-Intensity:
Fuel intake becomes crucial when exercise extends beyond 2.5 hours. Recommendations include consuming 60-90 g/hr of carbs. However, our gut is only capable of absorbing about 60-70 g/hr of one type of carb, therefore, it is suggested to ingest a combination of carb sources. This is what we refer to as “multiple transportable carbohydrates.” When consuming a combination of carb sources the body can absorb & utilize up to ~105 g/hr of carb, which results in greater amounts of fuel provided to the body to use as energy. This can be done by incorporating a combination of both glucose and fructose to maximize the absorption of carbs in your gut. Examples that fit this would be products such as sports gels, liquids, or chews. If you prefer to consume energy from real food sources, focus on carb-rich foods such as fruit, honey, or bars.
During exercise, there is a focus on consuming carbs that are easy to digest, as such high intakes can be a common challenge for many athletes due to GI distress. Some individuals experience diarrhea, cramping and other issues when consuming foods while training. This typically occurs due to an increased flow of fluid from the blood into the intestine. If you experience issues such as these, this is where experimenting with different carb amounts, timing, and types may be beneficial to find the best fueling strategy for you.
To help reduce GI upset, there are several factors to consider. First, there is promising evidence that multiple transportable carbohydrates, mentioned earlier, may help reduce GI distress. So, not only will you have increased absorption of carbs and fuel for the body, but potentially less cramping and intestinal distress as well. Second, it has been shown that regardless of carb form (solid vs gel vs liquid), each promotes similar glycogen resynthesis in the body. This allows you as an athlete some flexibility when choosing your carb sources and the form you consume them in. Lastly, they have found no differences in performance when carbs are either administered in a large bolus or spread throughout a prolonged bout of exercise. Therefore, you can find what may work best for you, either having a large amount at once or spreading smaller amounts throughout your training session.
There are many factors that play into how to properly fuel your training … you know your body best! So experiment with different carb sources, timing, and amounts. Take note of how different fueling strategies make you feel and how it impacts your overall performance. And although we focused on carbohydrate intake specifically during exercise, it is also important to keep in mind your carb intake before, after, and throughout the rest of your day. A lot plays into fueling your body appropriately, and it’s a continuous learning process. But with the proper knowledge and tools to support your body’s needs, you can keep the tank full and the engine running to crush your performance goals.
Kerksick, Chad M et al. “International society of sports nutrition position stand: nutrient timing.” Journal of the International Society of Sports Nutrition vol. 14 33. 29 Aug. 2017, doi:10.1186/s12970-017-0189-4
Asker E. Jeukendrup. “Carbohydrate feeding during exercise.” European Journal of Sport Science. 8:2, 77-86. 2008, doi: 10.1080/17461390801918971