Exercise intensity refers to how hard your body is working during physical activity. It can be measured in various ways, including heart rate, perceived exertion, or the amount of weight lifted. Higher intensity workouts typically lead to greater cardiovascular and muscular benefits, while lower intensity activities are often easier to sustain for longer periods. There are generally three levels of exercise intensity: low, moderate, and high. Low intensity includes activities like walking, while moderate intensity might involve brisk walking or cycling. High intensity includes activities such as running or heavy weightlifting, which require more effort and energy.