When it Comes to Endurance Performance - Separate Calories from Hydration

There is a growing trend for endurance athletes to replenish electrolytes and calories separately. Traditional sports drinks provide calories in the form of carbohydrates as well as essential electrolytes (sodium, potassium, calcium, magnesium). Often this combination is completely fine, but as training and event distances get longer, intensity increases or in extreme weather conditions, this single source approach has its draw backs.

Environmental Considerations

When temperature or humidity rise, our bodies must sweat more to keep us cool. This increases our need to rehydrate and replace lost electrolytes. Regardless of how hot or humid it is, our calorie requirements per hour remain pretty much the same. In fact, our body’s ability to digest carbohydrates actually decreases somewhat in hotter and more humid conditions because blood is diverted to the skin’s surface to cool us, leaving fewer resources available for the digestive system. This is actually a good thing. Our body’s survival instincts prioritize keeping us cool over getting additional calories. Heat stroke is much worse than bonking.

Training and racing in cold conditions creates the opposite challenge. Since we don’t sweat as much when it is cold, our hydration needs are not very high, but our calorie requirements don’t decrease. All of us have returned from a long effort on a cold day without drinking nearly as much as we would have on a hot summer day. The danger here is that if we are relying on our beverage for our calories, but are not drinking, we will not get the calories we could easily digest and utilize. 

Intensity Considerations

As intensity increases, our bodies use more resources to fuel muscles. The higher the intensity, the more heat we generate and thus additional resources are required to cool ourselves. To cool ourselves we sweat more, increasing our need to re-hydrate. During higher intensity exercise we consume more calories per hour, but our ability to digest calories at higher intensities decreases.

Avoid Too Many Calories

Too many calories during training or racing can prevent you from reaching the finish line. If you consume more calories than you can digest during exercise, those carbohydrates will linger in the digestive tract and actually inhibit the absorption of fluids. So not only will you not get the calories, it will slow your re-hydration efforts. Many endurance athletes report this experience as feeling “bloated” and uninterested or unable to eat or drink anything else. Worse than feeling bloated, this can also be the cause of severe stomach upset or other forms of GI distress.

Hydrate with Electrolytes, Refuel with Calories

A hydration strategy that separates rehydration and calories can eliminate the risks of over or under consuming calories.

Replenish electrolytes with your hydration. There are several brands of dissolvable effervescent electrolyte tablets on the market that provide balanced electrolytes with <10 calories each, including nuun tablets, Zym tablets and Hammer Endurolytes FIZZ. There are also low calorie  (60/per serving) energy drinks with electrolytes such as Accelerade Hydro or Enervit G Sport.

Get your calories from a separate source.  There are a wide variety of sources for getting the calories you need to fuel your endurance. These can be gels, bars, chews, or even other liquid sources. If you prefer getting your calories from a liquid then there is no problem mixing up a bottle of your favorite energy drink, just make sure it isn’t your only source. Many long course or ultra endurance athletes will mix a concentrated bottle of Hammer Perpetuem as a multi-hour bottle. You can do this with any sports drink. Consume your calories regardless of form (bars, gels, chews or liquid) on a regular schedule and rehydrate as you are thirsty. 

Nothing New On Race Day

As always, we recommend that you train with what you will use on race day. It is okay to tweak your hydration and nutrition plan based on the weather, distance or intensity, but you shouldn’t radically switch strategies. If you plan on using this strategy on race day, make sure you train with it as well.