The primary system improved by aerobic exercise is the cardiovascular system. Aerobic activities, such as running, swimming, or cycling, increase heart rate and improve blood circulation, leading to enhanced oxygen delivery throughout the body. This exercise helps strengthen the heart muscle and improve its efficiency, ultimately reducing the risk of heart disease and stroke. Additionally, regular aerobic exercise can lower blood pressure and improve cholesterol levels. Enhanced lung capacity and endurance are also beneficial outcomes, contributing to overall cardiovascular health and fitness.