In fitness activities, "cardio" refers to any exercise that elevates the heart rate, improving cardiovascular endurance and overall aerobic capacity. Common forms of cardio include running, cycling, swimming, and group fitness classes. These activities increase blood flow and oxygen delivery throughout the body, promoting heart health and calorie burning. Cardio also releases endorphins, which can enhance mood and reduce stress. Incorporating regular cardio workouts is vital for maintaining a balanced fitness regimen that promotes overall health and wellness.