What best defines "aerobic exercise"?

Aerobic exercise is best defined as sustained physical activity that increases heart rate. This type of exercise is characterized by activities that require continuous and rhythmic movement, such as running, swimming, cycling, or dancing. During aerobic exercise, the body uses oxygen to help produce energy, which is why heart rate increases to supply more oxygen to the muscles being worked.

In this context, while aerobic exercise does involve sustained activity, it specifically targets the improvement of cardiovascular fitness, endurance, and overall health by keeping the heart rate elevated over a longer period. This substantial increase in heart rate helps to improve efficiency in the heart and lungs, making aerobic exercise a crucial component of many fitness programs.

The other options, while describing different forms of physical activity, do not align with the specific definition of aerobic exercise. For example, decreasing heart rate would be contrary to the purpose of aerobic exercise, while short bursts of high-intensity workouts (often referred to as interval training) focus on anaerobic rather than aerobic conditioning. Flexibility exercises, on the other hand, do not primarily increase heart rate but rather emphasize the range of motion in the joints and muscles.