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To achieve peak nutrition, mountain athletes need to fuel their bodies with the appropriate amount of nutrients to create enough ATP, the body’s energy currency. This essential molecule carries the energy for every baseline process in the body, including the continuous muscle contractions that take place on those long slogs up to the summit. You need a constant stream of ATP to keep you moving and to keep pushing you toward your objectives. The more ATP you have, the more you can do. The kind of outdoor sports you do will determine how you spend the currency.

One of the essential laws of thermodynamics that pertain to mountain athletes is this: energy is never really created and it’s never really destroyed. Instead, energy is transferred from one entity to another. In a nutshell, the energy in the food you eat is converted into a usable form for the mountains you climb, as well as for the baseline energy needs of your body. If you take a closer look at the macronutrients in food, you’ll see that they are made up of organic molecules, with many carbon-hydrogen bonds. When these bonds break, you get a burst of energy that is used to fuel the process by which ATP is formed from ADP (adenosine diphosphate) and P (phosphate).

ATP use is triggered by nerve communication as you are about to contract a muscle. Although it can come from new nutrients, most of the ATP in your body comes from stored nutrients, so the food you ate yesterday or the day before will be used for today’s energy needs. The exception is long endurance activities, such as multipitch trad climbing, backcountry skiing, and big wall climbing, which require a lot more energy, so during these activities foods you consume at that moment will also be used for energy, in addition to stored energy. Otherwise, during most activities—including short-duration exercise (such as bouldering and lifting)—the energy you need comes from long-term stored nutrients in the liver cells, the muscle cells, and the fat cells. For these reasons, if you want to perform well in the future, it is important to have optimal nutrition quality and good daily eating habits.

The two most important stored nutrients that provide energy for ATP production are glycogen (carbs) and triglycerides (fats). When these nutrients are broken down into simpler forms, they generate enough energy to bind ADP + P into ATP and to act locally in the tissues where they are stored. These nutrients provide energy for cells that don’t have energy stores of their own, such as the brain and red blood cells. In times of low food intake (during fasting, extreme dieting, or very long endurance endeavors), they will continue to circulate through the body to provide cells with enough energy to generate ATP. This process is essential for survival.

Your body breaks down larger molecules into a more usable form:

Glycogen Glucose

Triglycerides Fatty acids or ketone bodies

Proteins Amino acids

ATP 101

To recap: You need a constant stream of ATP to carry out both your most basic and higher-level functions. The energy that is needed to generate more ATP comes from triglycerides and glycogen. It’s the breaking of the phosphate bonds in ATP that releases the energy for the task at hand—for example, muscle contractions and enzyme production. Once this bond is broken, it leaves us with ADP + P again, and the body will repeat the cycle of breaking carbon-hydrogen bonds to regenerate ATP.