Aerobic

Aerobic is an adjective derived from Greek "aero" for air and "bios" for life. In general usage, it describes processes that require or use air or oxygen. In biology, aerobic refers to cellular respiration that uses oxygen to extract energy from nutrients.

Aerobic respiration occurs in the mitochondria of cells and is the principal energy-producing pathway for many organisms. During aerobic respiration, substrates such as glucose are oxidized in the presence of oxygen to produce carbon dioxide, water, and adenosine triphosphate (ATP). This pathway yields far more ATP per molecule of glucose than anaerobic pathways.

In exercise science, aerobic exercise or cardio refers to sustained, rhythmic activities that rely mainly on aerobic metabolism to meet energy demands. Such activities include running, cycling, swimming, and brisk walking. They typically operate at moderate to high intensity for extended durations and can improve cardiorespiratory fitness, endurance, and metabolic efficiency. Training adaptations include increases in VO2 max, mitochondrial density, and capillary networks.

Aerobic and anaerobic are often contrasted. When oxygen supply is insufficient, cells rely more on anaerobic metabolism, producing lactate and less ATP. Aerobic processes are aerobic when oxygen is available; otherwise, anaerobic.