Rating of perceived exertion
The rating of perceived exertion (RPE) is a subjective psychophysical scale used to quantify an individual's conscious perception of the effort, fatigue, and strain experienced during physical activity, serving as a simple tool to monitor exercise intensity without relying on objective physiological measurements.[1] Developed by Swedish psychologist Gunnar Borg in the early 1960s through studies on psychophysical scaling methods, the RPE scale correlates strongly with indicators like heart rate (e.g., an RPE of 15 approximates a heart rate of 150 beats per minute) and oxygen uptake, making it a valid and reliable complement to traditional metrics.[2][3] Borg's initial research, conducted at Umeå University starting in 1959–1960, involved short-duration cycling exercises to explore discrepancies in perceived effort, building on earlier observations by Hans Dahlström and applying ratio-scaling techniques like magnitude estimation.[1] A foundational publication, "Perceived exertion as an indicator of somatic stress" (1970), formalized RPE as a multidimensional construct encompassing sensations of central (e.g., breathing) and peripheral (e.g., limb effort) fatigue, emphasizing its role in assessing overall somatic stress during activity.[2] Over time, Borg refined the approach in his 1998 book Borg's Perceived Exertion and Pain Scales, addressing misconceptions and expanding its theoretical basis to include neurophysiological elements like corollary discharges from motor commands and afferent feedback from muscle afferents.[4] The original Borg RPE scale is a 15-point category scale ranging from 6 ("no exertion at all") to 20 ("maximal exertion"), with verbal descriptors (e.g., 11 as "light" and 17 as "very hard") to guide ratings and ensure equidistant perceptual intervals.[1] A later iteration, the Category-Ratio (CR-10) scale, introduced in the 1980s, uses a 0–10 range (0 = "nothing at all," 10 = "maximal" or "extremely strong," with options for decimals and values exceeding 10) to provide finer granularity and avoid ceiling effects in high-intensity scenarios.[3] Both scales have demonstrated high validity across populations, including athletes and clinical patients, with test-retest reliability coefficients often exceeding 0.90.[5] In practice, RPE finds broad applications in exercise physiology, sports training, and rehabilitation, enabling load monitoring (e.g., via session-RPE for total training volume) and personalized intensity prescription without equipment.[5] Its validity is supported by meta-analyses showing strong correlations (r > 0.70) with criteria like blood lactate and ventilatory thresholds, particularly in adolescents and adults during aerobic and resistance exercises.[6] Despite cultural adaptations needed for diverse groups, RPE remains a cornerstone for safe, effective physical activity assessment due to its simplicity and robustness.[7]Definition and Overview
Core Concept
Rating of perceived exertion (RPE) is a subjective measure that quantifies an individual's perception of the intensity of physical activity, serving as a cognitive integration of multiple physical sensations associated with effort, fatigue, and discomfort during exercise. This perception arises from the brain's processing of signals from the body, forming a holistic sense of how demanding the activity feels.[8] RPE encompasses an overall assessment of exertion by synthesizing inputs from various physiological systems, including respiratory strain (such as breathlessness), muscular discomfort (like localized fatigue or burn), and cardiovascular responses (evidenced by sensations of increased heart rate or pounding).[3] These sensations are not isolated but combined into a unified subjective experience that reflects the total burden of the activity on the body. In contrast to objective physiological metrics—such as heart rate, which can be measured via monitors, or oxygen uptake (VO₂), assessed through gas analysis—RPE is fundamentally a psychological construct, relying on personal interpretation rather than external quantification.[9] This subjectivity allows RPE to account for individual variability in tolerance and experience, making it distinct from purely biomechanical or biochemical indicators.[3] The core process of RPE involves self-reporting, where the individual rates their perceived effort either in real-time during the exercise or retrospectively immediately afterward, providing a simple, non-invasive way to gauge intensity.[9] Standardized scales, such as those developed by Borg, facilitate this quantification by offering a structured framework for expressing the subjective rating.Significance in Health and Exercise
Rating of perceived exertion (RPE) serves as a subjective, non-invasive, and real-time method for assessing exercise intensity, requiring no specialized equipment or physiological monitoring, which enhances its practicality for use in diverse settings such as field training or home-based programs.[10] This accessibility allows individuals to gauge their effort based on internal sensations of fatigue, breathing, and muscle discomfort, facilitating immediate adjustments during activity without external devices.[11] By providing a personalized measure of exertion, RPE promotes safer and more effective exercise experiences across various intensities and durations.[12] In exercise contexts, RPE plays a crucial role in preventing overtraining by enabling the monitoring of cumulative training load through methods like session-RPE, where perceived effort is multiplied by session duration to quantify overall strain and detect early signs of fatigue accumulation.[13] This approach helps optimize athletic performance by supporting periodized training plans that balance intensity and recovery, reducing the risk of injury and illness while enhancing adaptations to physical demands.[14] Furthermore, RPE fosters greater adherence to exercise regimens by aligning workout intensity with an individual's tolerance and comfort, encouraging sustained participation in physical activity for long-term health benefits.[13] RPE finds broad application among diverse populations, including elite athletes who use it to self-regulate pacing and maintain optimal effort during competitions and training.[12] In clinical settings, such as cardiac rehabilitation programs for patients recovering from procedures like percutaneous coronary intervention or myocardial infarction, RPE guides safe intensity progression, helping participants achieve meaningful improvements in functional capacity without overexertion.[15] For general fitness enthusiasts, its simplicity supports everyday monitoring of moderate activities, making it a versatile tool for promoting physical activity in non-athletic or sedentary individuals.[16] Studies demonstrate RPE's utility in establishing dose-response relationships for exercise benefits, particularly in cardiovascular health, where appropriate intensity levels prescribed via RPE contribute to enhancements in cardiorespiratory fitness and reductions in mortality risk through incremental metabolic equivalent gains.[15] For instance, in cardiac patients, RPE-guided sessions have been associated with significant increases in peak oxygen uptake and workload capacity, underscoring its value in tailoring exercise to yield protective health outcomes.[15] RPE also correlates moderately with objective measures like heart rate, providing a reliable proxy for intensity in resource-limited environments.[12]History and Development
Gunnar Borg's Contributions
Gunnar Borg (1927–2020) was a Swedish psychologist and professor emeritus of perception and psychophysics at Stockholm University, where he founded the Borg Perceptional Research Unit to advance studies in subjective sensory scaling.[17] Born on November 28, 1927, Borg earned degrees in psychology, philosophy, education, and physiology, and held positions including associate professor at Umeå Medical School (1966–1967) and director of the Institute of Applied Psychology at Stockholm University (1968–1980).[18] His academic career focused on applying psychophysical principles to human sensations, establishing him as a pioneer in quantifying subjective experiences.[1] In the 1960s and 1970s, Borg conducted foundational research on the psychophysics of perceived exertion, examining how individuals subjectively experience effort during physical activities such as cycle ergometer exercises.[1] He employed methods like ratio production and magnitude estimation to link subjective ratings of exertion to objective physiological measures, including heart rate and oxygen uptake, revealing a power function relationship with an exponent of approximately 1.7 between workload and perceived intensity.[1] This work emphasized perceived exertion as a holistic "Gestalt" integrating sensations from muscles, skin, respiration, and circulation, providing a reliable indicator of somatic stress.[19] Borg developed the category-ratio scaling approach to measure such sensations, creating prototypes for rating perceived exertion that anchored verbal descriptors to numerical ratios for inter-individual comparability.[1] This innovative framework, rooted in psychophysical laws, allowed for the quantification of effort without relying solely on physiological monitoring.[20] His contributions laid the groundwork for subsequent scales, including the CR-10.[1] Key publications include Borg's 1970 paper, "Perceived Exertion as an Indicator of Somatic Stress," which outlined the concept's application in rehabilitation and stress assessment, and his 1982 work, "Psychophysical Bases of Perceived Exertion," which detailed ratio-scaling and category methods for effort ratings.[2][20] These seminal texts, along with over 250 scientific papers, solidified Borg's influence in exercise physiology and ergonomics.[17]Evolution and Adaptations
Following Gunnar Borg's foundational work on perceived exertion scales in the mid-20th century, adaptations in the 1980s focused on enhancing the range and psychophysical properties of these tools. In 1982, Borg introduced the Category-Ratio (CR-10) scale, designed to accommodate a broader spectrum of intensity levels beyond the original 6-20 category scale, enabling more precise ratio-based assessments of exertion across diverse activities. This modification addressed limitations in capturing extreme efforts by incorporating a nonlinear, accelerating growth function aligned with human sensory perception.[21] During the 1990s and 2000s, RPE methodologies expanded significantly through integrations with physiological metrics and applications in sports science. A key development was the widespread adoption of heart rate prediction formulas, such as HR ≈ RPE × 10 (derived from the 6-20 scale), which linked subjective ratings to objective cardiovascular responses for training load estimation.[22] Concurrently, the session-RPE (sRPE) method emerged around 1996 as a practical modification, multiplying a single post-session RPE rating by session duration to quantify global training load, facilitating its routine use in athletic monitoring and overtraining prevention.[23] These advancements solidified RPE's role in sports science, with studies demonstrating its correlation to internal loads like heart rate and lactate thresholds. In recent years (2020-2025), RPE has seen heightened application in specialized domains, including resistance training, where distinctions between set RPE (overall effort per set) and rep RPE (effort per repetition) allow for autoregulated programming to optimize hypertrophy and strength while minimizing fatigue.[24] Adaptations for older adults emphasize RPE-based prescriptions to promote safe resistance exercise adherence and functional improvements, rebranding traditional protocols to reduce intimidation and enhance self-efficacy.[25] Digital innovations, such as mobile apps and wearable integrations, now enable real-time RPE tracking during sessions, supporting personalized feedback in both clinical and athletic settings.[26] Scoping reviews from 2024-2025 have further mapped RPE's utility in continuous sports like running and cycling, highlighting evidence gaps in measurement reliability across contexts while affirming its validity for load management.[27] Minor scales, such as the OMNI system with pictorial anchors, emerged in the late 1990s and early 2000s as adaptations for children and adolescents, using visual cues to improve comprehension and validity in pediatric populations during activities like walking or cycling.[28]RPE Scales
6-20 Borg Scale
The 6-20 Borg Scale, developed by Gunnar Borg, is a 15-point category scale designed to quantify perceived exertion during physical activity, ranging numerically from 6 to 20 in increments of 1.[20] Verbal anchors provide qualitative descriptors at key points to assist in rating overall bodily sensations of effort, such as increased breathing, heart pounding, muscle fatigue, and sweating. The scale's anchors are as follows:- 6: No exertion at all
- 7: Extremely light
- 8:
- 9: Very light
- 10:
- 11: Light
- 12:
- 13: Somewhat hard
- 14:
- 15: Hard (heavy)
- 16:
- 17: Very hard
- 18:
- 19: Extremely hard
- 20: Maximal exertion[3]