The right answer is A. Decrease in fat stores.
Fats, or lipids, are the main source of energy for our body. They are stored as triglycerides in adipocytes, cells that make up adipose tissue.
Lipolysis is the process of breaking down fat into energy that can be used by the muscles. Glucagon, secreted by the pancreas, and adrenaline, secreted by the nervous system and the adrenal glands, break down triglycerides into glycerol and fatty acids, the latter serving as fuel for the muscles.
During a physical exercise of the aerobic (endurance) type, our muscles consume the glucose present in the blood or resulting from the transformation of the glycogen in reserve in the muscles and the liver. These reserves are available immediately or almost but they are limited: they alone can provide an intense effort of about 90 minutes. After a few minutes of effort, the destocking of fats intervenes and supplements the energy provided by carbohydrates.
