what is exercise intensity?

Exercise intensity refers to how hard the body is working during physical activity, or how much energy is being expended in the process. It measures the physical effort put forth and can be expressed as a percentage of maximal oxygen consumption (VO2 max) or through heart rate. Exercise intensity influences the fuel used by the body and the physiological adaptations resulting from the workout. It can be categorized into levels such as low, moderate, and vigorous intensity, each having different health and fitness effects. Methods to measure intensity include subjective perceived exertion and objective heart rate monitoring. For example, moderate intensity is often described as the level of effort where one can still talk but not sing during the activity.