Aerobic exercise

Aerobic exercise, often called "cardio," is physical activity that relies on oxygen to produce energy. The term "aerobic" specifically means relating to or requiring oxygen. This type of exercise involves repeating sequences of light-to-moderate intensity activities for extended periods.

Unlike short bursts of power, aerobic movement is sustained over time. It is a vital part of maintaining human health and physical fitness. Scientists study how the body uses oxygen to meet these energy demands through aerobic metabolism.

To understand how it works, we must look at the cellular level. Inside your cells are tiny structures called mitochondria, which are organelles that act as power plants. These mitochondria rely on oxygen to metabolize carbohydrates, proteins, and fats into energy. During aerobic exercise, the body uses oxygen to turn all available carbohydrates into energy through mitochondrial ATP production.

This process can actually cause a remodeling of the mitochondrial cells. This change happens within the tissues of the liver and the heart to improve efficiency. As you move, your body chooses different fuels based on how hard you work.

At lower intensities, the body preferentially uses fat, known as adipose tissue, as its main fuel source for cellular respiration. However, as the intensity of the exercise increases, the body shifts its preference. It begins to use glycogen, which is a carbohydrate stored in the muscles and liver, because it provides a quicker source of energy. Amino acids can also be used, though they only provide about 3% of the total energy expenditure. This shift in fuel usage is a key part of how the body manages its energy stores during different types of movement.

Aerobic exercise can be categorized by its intensity and the specific movements involved. Moderate activities include walking, gardening, light yard work, or doubles tennis. Vigorous activities include brisk walking, uphill hiking, soccer, or singles tennis.

Some sports are inherently aerobic, like long-distance running or cycling. Others, like rowing, are aerobic but involve many different muscle groups, including the legs, abdominals, chest, and arms. This is distinct from anaerobic exercise, such as sprinting or heavy strength training, which uses different energy-generating processes like glycolysis and the phosphocreatine system.

The history of understanding aerobic capacity is filled with significant scientific milestones. In 1922, British physiologist Archibald Hill introduced the concepts of maximal oxygen uptake and oxygen debt. That same year, Hill and German physician Otto Meyerhof shared the Nobel Prize in Physiology or Medicine for their work on muscle energy metabolism.

In the 1950s and 1960s, researchers like Henry Taylor, Per-Olof Åstrand, and Bengt Saltin made further contributions. Later, Dr. Kenneth H. Cooper, known as the "father of aerobics," began researching preventive medicine. He studied over 5,000 U.S. Air Force personnel and coined the term "aerobics" in 1966.

Regular aerobic activity offers many measurable health benefits. It can strengthen the heart muscle, which improves pumping efficiency and lowers the resting heart rate. It also increases the total number of red blood cells, helping the body transport oxygen more effectively. Research shows that aerobic exercise can reduce the risk of diabetes by helping to lower Hb A1C levels.

Even small amounts are helpful; performing just 75 minutes of exercise per week can reduce the risk of early death, stroke, and cancer. To reduce general health risks, experts recommend 2.5 hours of moderate-intensity aerobic exercise every week.

While beneficial, there are risks to consider if exercise is not managed correctly. Repetitive movement can lead to overuse injuries in the musculoskeletal system, especially in athletes under age 19. High volumes of training without enough calories can lead to RED-S, particularly in female athletes. It is also important to remember that different methods have different efficiencies. For example, High-intensity interval training (HIIT) can provide similar benefits to aerobic exercise in much less time. To maintain health, athletes must balance their activity with adequate recovery and nutrition.