When does anaerobic metabolism accelerate?

Anaerobic metabolism accelerates after reaching the anaerobic threshold. This threshold is the point during exercise at which the body starts to rely more on anaerobic pathways for energy production, typically due to an increased demand for energy that surpasses the supply of oxygen available to the muscles. During high-intensity activities, where the body’s oxygen supply cannot meet the energy demands quickly enough, anaerobic metabolism kicks in to generate energy rapidly, primarily through the breakdown of glucose without oxygen.

At this stage, lactic acid is produced as a byproduct, and while this allows for sustained efforts during intense bouts, it also signals that fatigue can set in more quickly compared to aerobic metabolism, which utilizes oxygen and is more efficient for longer-duration activities. In contrast, other scenarios such as low-intensity exercise and when there is an abundance of oxygen reliance lean more heavily on aerobic metabolism, while achieving steady state indicates the metabolic systems have stabilized and are efficiently utilizing oxygen for energy.