There are three energy systems. They each work a little differently in the human body and each utilizes different types of foods. It is possible, in a sense, to fuel each system. Here’s the simple version of the biochem going on in your body when you are training:
The Adenosine Triphosphate – Phosphocreatine, or ATP PC is an anaerobic system. This means it does not use oxygen. It is used during intense and explosive movements such as sprints or lifts. The ATP PC system generates ATP rapidly, but only for about 3-15 seconds because the creatine stored in the muscles is limited. 1 ATP per 1 PCr is produced.
What happens in the body -> the creatine kinase enzyme breaks phosphorus and creatine apart, the phosphorus combines with adenosine diphosphate (ADP) to form ATP
Foods that fuel this system -> Foods containing creatine, such as meat, fish, and dairy products. Creatine can be synthesized in the body from arginine, glycine, and methionine, found in nuts and seeds. Creatine monohydrate supplements work to ensure the highest level of stored creatine is in the muscles before working out.
Glycolysis is an anaerobic system and does not use oxygen. It is used during moderate-intensity exercises under one minute. Glycolysis generates ATP rapidly, but does not produce a lot of ATP, about 2-3 ATP, and lasts for about 15-50 seconds and limited by lactate build up.
What happens in the body -> one glucose molecule containing 6 carbons is oxidized and to form two pyruvic acid molecules. ATP is generated directly from the breakdown process of glucose to pyruvate. ATP is also generated when hydrogen molecules that are removed in oxidation are transported through the electron transport chain to produce ATP aerobically.
Foods that fuel this system -> Carbohydrates, such as whole grains, beans, fruits, and vegetables.
Oxidative Phosphorylation is an aerobic system. This means it uses oxygen. It is used during longer events such as running, swimming, biking, or rowing. The oxidative system generates fairly unlimited ATP as long as macronutrients and oxygen are of sufficient supply and 38-39 ATP produced in a cycle.
What happens in the body -> Glucose and fat oxidation produces Acetyl CoA, which is oxidized and combined with oxaloacetate to shuttle into the Krebs cycle. Hydrogen molecules are produced and sent to the electron transport chain where ATP is produced.
Foods that fuel this system -> All carbohydrates, fats, and proteins.