Aerobic exercise is sustained physical activity that raises heart rate and breathing rate enough to improve the capacity of the cardiovascular and respiratory systems. Running, swimming, cycling, and brisk walking are typical examples.

The immediate effect is an increase in oxygen demand. The heart pumps harder, the lungs take in more air, and blood is delivered more efficiently to working muscles. Over weeks and months of regular training the body adapts: stroke volume increases, resting heart rate falls, capillary networks expand, and mitochondria become more numerous. The result is greater endurance and a lower risk of heart disease, stroke, and type 2 diabetes.

Psychological benefits are equally well documented. Aerobic activity reduces symptoms of mild to moderate depression and anxiety, improves sleep, and can enhance certain aspects of cognitive function, especially in older adults. The mechanisms include the release of endorphins, reduced inflammation, and the growth of new neurons in the hippocampus.

Guidelines typically recommend at least 150 minutes of moderate aerobic activity per week. The exact form matters less than consistency. A body that moves regularly stays more capable for longer.