From which organ does glucose energy used for aerobic activity primarily come?

The liver primarily provides glucose energy for aerobic activity through a process called gluconeogenesis, where it generates glucose from non-carbohydrate sources, and through glycogenolysis, which involves breaking down glycogen stores into glucose. This glucose is then released into the bloodstream to supply energy to muscles and other tissues that require it during aerobic exercise.

The heart, while it does utilize glucose for energy, primarily depends on fatty acids and relies on the myocardium's own stores and the circulation of nutrients rather than being a source of glucose. The pulmonary system is involved in gas exchange, specifically oxygen intake and carbon dioxide removal, rather than glucose metabolism. The kidneys play a crucial role in homeostasis and filtering waste but are not a primary source of glucose energy for aerobic activities. Thus, the liver stands out as the organ that supplies glucose effectively during sustained aerobic exercise.