The Rate of Perceived Exertion (RPE) is a subjective tool used to quantify the intensity of physical activity, measuring how hard a person feels they are working during exercise. Developed in the 1960s by Swedish researcher Gunnar Borg, RPE is now a central concept in exercise science and self-monitoring for athletes and general exercisers. This scale integrates various bodily sensations into a single number, offering a practical way to assess effort. RPE allows individuals to adjust their training intensity based on their current physical feeling, making it an invaluable method for managing exercise loads and progress.
Defining the Feeling of Exertion
Perceived exertion is a conscious sensation that integrates a variety of signals sent from the body to the brain during physical activity. It represents the subjective interpretation of physical strain, heaviness, and strenuousness. This feeling is not based on a single physiological measure but rather a configuration of information from multiple systems.
The body communicates its level of effort through several key physiological inputs. From the muscles, the brain receives signals related to localized strain, fatigue, and metabolic byproducts like lactic acid. Concurrently, the cardiovascular and respiratory systems provide feedback through increased heart rate and breathlessness. These signals are combined with input from the central nervous system, contributing to the overall sense of effort. The resulting RPE score is the individual’s unique, subjective rating of these objective physical responses.
Standardized Measurement Scales
To turn this subjective sensation into a usable metric, standardized scales were created, starting with the original Borg Scale. This initial scale ranges from 6 to 20, where 6 signifies “no exertion at all” and 20 signifies “maximal exertion.” The rationale behind starting at six was its intended correlation with heart rate; multiplying the RPE score by 10 would approximate the person’s heart rate during the activity. For example, a rating of 13, described as “somewhat hard,” corresponds roughly to a heart rate of 130 beats per minute.
A more commonly used version today is the modified Borg Category-Ratio Scale, often simplified to the RPE 1-10 scale. This scale is more intuitive for the average person, with 1 representing “very light” activity and 10 representing “maximum effort.” A rating of 3 often corresponds to light activity where conversation is easy, while an RPE of 7-8 represents vigorous activity where talking is difficult. This 1-10 scale is particularly favored in strength training, where an RPE 10 means the individual could not complete another repetition.
Applying RPE to Exercise Intensity
The practical application of RPE lies in its ability to autoregulate training loads, allowing exercisers to adjust their effort in real-time based on internal feeling. Instead of rigidly adhering to a specific speed or weight, a person aims for a target RPE to ensure consistent workout quality. For a distance runner, this might mean maintaining an RPE of 6 for a long, steady-state run, slowing down if the effort begins to feel like a 7.
In resistance training, RPE is used to select the appropriate weight for a given set, ensuring the exercise stimulates adaptation without leading to excessive fatigue. For muscle growth, a lifter might aim for an RPE of 7 or 8, meaning they finish the set knowing they had two to three repetitions remaining before failure. The RPE score serves as a feedback loop, guiding the athlete to adjust the objective workload—such as pace or weight—to match the intended subjective intensity. This approach allows for a dynamic training plan that honors the body’s daily fluctuations in capacity.
Internal and External Factors That Change RPE
While RPE is founded on physiological signals, the final rating can be significantly influenced by factors beyond the immediate physical workload. Environmental conditions play a large role; exercising in high heat, humidity, or at a higher altitude will increase the RPE for the same objective output.
Internal, non-physiological factors, such as psychological state, also cause RPE to fluctuate daily. High levels of life stress, poor sleep quality, or low motivation can contribute to a higher perceived exertion, even if physical fitness has not changed. Recovery status, including hydration and nutrition, similarly impacts how difficult a workout feels.