An introduction to Borg's RPE-scale.
Humans have a very well-developed capacity to assess the level of exertion.
Associated feelings provide essential information that is important for determining the welfare or extent of threat to an individual. The perception of exertion is a monitoring behavior that uses all sources of information to govern actions that can benefit or preserve health and partake of adaptive pursuits. How one feels about exertion moderates the response to exercise and effort. Thus, the perception of what is happening in exercise, and its concomitant effect on physiological function, needs to be known to further understand the nature of an exercise response. How one feels modifies reactions to exercise stress and the mechanisms that underlie them.