Should You Eat or Drink Your Calories?

Bonk or cramp? There's a thin line between the two and that's the line triathletes walk in long-distance training and racing. If you don't take in the right amount of food and fluid, you'll bonk. Take in the wrong stuff, or at the wrong rate, and you face a wide array of GI issues, cramping among the least of them.

So how do you get the calories and fluid you need without taxing your GI system? This article compares the two primary fueling methods triathletes use while training and racing—chewing calories versus drinking them.

There is general consensus among coaches, exercise physiologists and nutritionists that for training sessions and races beyond two hours, athletes should supplement with something in order to maintain their performance output. When an athlete's glycogen stores drop too low, they experience significant fatigue and a sharp decrease in performance. In its most extreme form, athletes hit the wall or bonk.

More: What You Need to Know About the Dreaded Bonk


That's where energy drinks and bars come in—to provide a ready-made energy supply that helps athletes continue to train and race at their best.

But, eat too much or at the wrong times and you can experience all types of complications in the form of gastrointestinal (GI) problems, stomach aches and nausea, which can slow you down. Alternatively, if you don't consume enough fuel, you can experience early fatigue and a decrease in performance. Finding the right balance is imperative.


In addition to fueling, athletes need to hydrate to perform well. Let's highlight two of the ways dehydration negatively affects the body.

First, as blood plasma depletes due to dehydration, the heart's stroke volume—the volume of blood pumped per heartbeat—diminishes. Due to this reduced cardiac output the heart has to pump faster just to deliver the same number of oxygenated blood cells to working muscles. This phenomenon is known as cardiac drift and reflects the additional stress heat places on the body. If you've ever experienced an elevated heart rate that stays way above your effort level, you've probably experienced this phenomenon.

Second, dehydration compromises the body's thermoregulatory response and its ability to stay in homeostasis. As part of the body's cooling mechanism, it pulls heat away from the body through sweat evaporation. The body also cools through the principals of convection (dispersal of heat through blood circulation) and conduction (body heat radiating away). The blood vessels expand to allow additional blood to circulate into the superficial capillaries in the skin to pull heat away from the body.

More: Cracking the Code on Sweat Rates

Without taking in additional fluids, your body can only perform for so long without purposely slowing down to protect the vital organs from overheating. You can usually tolerate up to a 2 to 3 percent loss in body water and still perform, but beyond that you may start to develop minor symptoms such as headaches, dizziness, nausea, disorientation and sluggishness.

Ultimately, athletes need to manage the twin perils of glycogen depletion and dehydration in order to perform at peak levels in events lasting longer than 2 to 3 hours, and especially in hot and humid conditions. For hot Ironman events such as Kona, it's imperative to nail down a solid nutrition and hydration strategy.

More: The Fourth Discipline

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