RPE (Rate of Perceived Exertion) variables refer to the subjective assessment of an individual's level of effort and intensity during physical activity. It is a scaling system where individuals rate their perceived exertion on a numerical scale, typically from 6 to 20, with 6 being no exertion and 20 being maximal exertion. This scale is used to monitor and adjust training intensity and workload. RPE variables can include factors such as physiological fatigue, psychological motivation, and environmental conditions.