Anaerobic exercise is a type of exercise that breaks downglucose in the body without using oxygen, as anaerobic means “without oxygen”. In practical terms, this means that anaerobic exercise is harder but shorter than aerobic exercise. The biochemistry of anaerobic exercise involves a process called glycolysis, in which glucose is converted to adenosine triphosphate, which is the primary source of energy for cellular reactions. Lactic acid is produced at an increased rate during anaerobic exercise, causing it to build up quickly. The build-up of lactate above the lactate threshold is a major contributor to muscle fatigue. Anaerobic exercise may be used by personal trainers to help their clients build endurance, muscle strength, and power.
Metabolism
is a natural part of metabolic energy expenditure. Fast twitch muscles operate using anaerobic metabolic systems, such that any use of fast twitch muscle fibers leads to an increased anaerobic energy expenditure. Intense exercise lasting upwards of four minutes may still have considerable anaerobic energy expenditure. An example is High-intensity interval training, an exercise strategy that is performed under anaerobic conditions at intensities that reach an excess of 90% of the maximum heart rate. Anaerobic energy expenditure is difficult to accurately quantify. Some methods estimate the anaerobic component of an exercise by determining the maximum accumulated oxygen deficit or measuring the lactic acid formation in muscle mass. In contrast, aerobic exercise includes lower intensity activities performed for longer periods of time. Activities such as walking, jogging, rowing, and cycling require oxygen to generate the energy needed for prolonged exercise. For sports that require repeated short bursts of exercise, the aerobic system acts to replenish energy stores during recovery periods to fuel the next energy burst. Therefore, training strategies for many sports demand that both aerobic and anaerobic systems be developed. The anaerobic energy systems are:
High energy phosphates are stored in limited quantities within muscle cells. Anaerobic glycolysis exclusively uses glucose as a fuel in the absence of oxygen, or more specifically, when ATP is needed at rates that exceed those provided by aerobic metabolism. The consequence of such rapid glucose breakdown is the formation of lactic acid. Physical activities that last up to about thirty seconds rely primarily on the former. Beyond this time, both aerobic and anaerobic glycolysis-based metabolic systems are utilized. The by-product of anaerobic glycolysis—lactate—has traditionally been thought to be detrimental to muscle function. However, this appears likely only when lactate levels are very high. Elevated lactate levels are only one of many changes that occur within and around muscle cells during intense exercise that can lead to fatigue. Fatigue, that is muscle failure, is a complex subject that depends on more than just changes to lactate concentration. Energy availability, oxygen delivery, perception to pain, and other psychological factors all contribute to muscular fatigue. Elevated muscle and blood lactate concentrations are a natural consequence of any physical exertion. The effectiveness of anaerobic activity can be improved through training. Anaerobic exercise also increases an individual's basal metabolic rate.
