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Scientific Rationale for RPE Use in Fitness Assessment and Exercise Participation

Kilpatrick, Marcus Ph.D., FACSM; Newsome, A’Naja M.S.; Foster, Carl Ph.D., FACSM; Robertson, Robert Ph.D., FACSM; Green, Matt Ph.D., FACSM

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ACSM's Health & Fitness Journal: 7/8 2020 - Volume 24 - Issue 4 - p 24-30
doi: 10.1249/FIT.0000000000000587
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Physical exertion is a universal part of the exercise experience. Measurement of the rating of perceived exertion (RPE) has become almost as common in exercise physiology and fitness assessment as heart rate (HR) and oxygen consumption (V̇O2). This article aims to present a scientific rationale for the use of RPE in exercise testing procedures and training intensity regulation. Knowledge related to RPE can provide benefit to practitioners in their work with patients, clients, and athletes. The effective use of RPE for both exercise testing and fitness programming can enhance the process of improving health and fitness.


RPE is defined as the degree of heaviness and strain experienced in physical work (1). RPE is both a quantitative and subjective measure of exercise intensity. It is quantitative in that standardized scales are typically used for assessment. It is highly subjective in nature because exertion is derived by asking an exerciser how they perceive the difficulty of exercise. The development and initial use of perceived exertion in the 1960s by Swedish psychologist Gunnar Borg was based on the premise that in humans the perception of exertion associated with physical work increases as a function of the intensity of the physical stimulus (1). Early field experiments by Borg used RPE and work capacity determined during cycle ergometry to predict the productivity of Swedish lumberjacks while considering the amount of effort they expended occupationally. These early studies contributed to our understanding of the relationship between perceptions of effort and physiological responses.


The innovative work by Borg and colleagues more than 50 years ago resulted in the development of the internationally recognized Borg 6–20 RPE scale (1). This original category scale was configured based on observations that resting HR for a young adult was about 60 beats per minute, and maximal HR was about 200 beats per minute (2). This scale removed the zero from these HR values and proposed that RPE at rest would be 6 and RPE at maximal exercise would be 20. The idea was that an RPE of 11, described as “fairly light,” would correspond to an HR of about 110 beats per minute and an RPE of 17, described as “very hard,” would correspond to an HR of about 170. Noteworthy is that the underlying scaling was designed to be linear so as to match the relatively linear increases associated with HR. Although these assumptions were not perfect, the underlying premise was reasonable and the link between RPE and intensity is strong enough to be useful.

The Borg 6–20 scale has remained a popular exertion scale in a wide range of exercise contexts because it has proven to be an excellent subjective indicator of exercise intensity. An important consideration related to the Borg 6–20 scale, however, is that the numerical range of 6 to 20 is not easy for all exercisers to conceptualize when estimating effort, which can interfere with effective use. Borg later developed a category-ratio (CR) scale, commonly known as the CR-10 scale, which assumes that exertion changes in a curvilinear manner as exercise intensity increases (3). This scale provides an alternative to the original 6–20 scale and creates some advantages both in terms of practical use and in describing how perceptions of effort are affected by workload. Noteworthy is that the range of this scale extends beyond 10 to “absolute maximum” and includes verbal markers such as “extremely weak” and “very strong” that are appropriate when the exerciser conceptualizes RPE as the intensity of the signal that is causing the sensation of effort, but these terms may not seem intuitive for exercisers who are simply reporting “how hard” the exercise intensity is. These two Borg scales have been extensively validated (3) and are widely used both in research and practice because they both work well.

An increasingly popular variant within practical settings are OMNI scales, where the scale name stands for “omnibus,” which means “pertaining to numerous things at once” and thus reflects the underlying idea that RPE responses result from a myriad of factors (4). OMNI scales have 0 and “extremely easy” representing the lowest level of exertion, whereas 10 and “extremely hard” represent maximum exertion. This logical numerical scaling range with easily understood descriptors coupled with a pictorial system conveying effort through progressive changes in body language of the exerciser provides many potential advantages. A variety of tools and methodologies are available for practitioners based on their intended population and training modalities. Variations of the OMNI scales have been developed for a wide variety of exercise modalities, including cycling, walking/running, step exercise, and resistance exercise. An important consideration is that each of the RPE scales mentioned thus far have been and are being effectively used both in research and practice, reinforcing the essential validity of Borg’s original concept that perceived exertion links physiological and perceptual variables to create an index of exercise intensity. The inherent advantages of the OMNI system for practitioners have resulted in an increase in the use of RPE in practical exercise settings. Each of these scales is provided within Figure 1.

Figure 1
Figure 1:
Commonly used RPE scales.


Measurement of exertion was established by Borg who determined that the perceptual and physiological aspects of exercise are linked. This basic principle allows for enhanced understanding of RPE. The model depicted in Figure 2 suggests that engaging in exercise serves as the initial stimulus, which creates an exercise experience ultimately resulting in the formulation of an RPE response given by the exerciser. The RPE could be expressed in an undifferentiated manner for overall body (i.e., RPE-Overall) or specific body aspects (i.e., RPE-Arms, RPE-Legs, RPE-Breathing). It is important to note that physiological, psychological, performance, and somatic factors interact together in dynamic ways to produce an overall experience that leads to an RPE response (2). Physiological factors include variables such as HR, metabolic rate, ventilation, metabolic acidosis, and blood flow (5). Psychological factors include elements such as mood state, motivation, task preferences, overall exercise experience, and subjective fatigue (5). Performance factors consider the strategy, duration, and distance of the exercise task, the competitive history, and the impact of an audience (5). Finally, somatic factors include sensations related to sweating, skin or body temperature, and muscular or joint discomfort (5).

Figure 2
Figure 2:
Model of RPE.

The subjective response to exercise is based on the combination of physiological, psychological, and performance factors.

These factors combine and are processed by the individual exerciser to form a perceptual response that is measured as the RPE, which is strongly related to a variety of physiological variables, including HR, muscle and blood lactate, and oxygen consumption (5). In each case, increases in these objective physiological markers are associated with increased RPE. Noteworthy is that RPE and these and other variables track together remarkably well, and changes in RPE can be used as a proxy for changes in more traditional markers of exercise intensity. This relationship allows RPE to serve as a complement to objective measures and also may reduce the reliance on a multitude of variables that are not always easily measured in the practical ways that exercise the desire of physiologists and fitness professionals. Based on these observations, the practitioner can effectively use RPE largely because of the consistent link this subjective measure has with more traditional objective measures of exercise intensity. However, practitioners also are encouraged to simultaneously collect and assess other measures as seem appropriate for the specific situation so as to have multiple sources of information from which to make decisions about the need to adjust workloads. HR represents the easiest of the many objective measures because of the availability of accurate monitors that are worn on the wrist or strapped to the chest.

RPE is highly correlated with a variety of physiological variables, including HR, muscle and blood lactate, oxygen consumption, ventilation.


A primary consideration for practitioners is the need for confidence that the tools and devices they use with patients and clients are doing the job they are intended to do. RPE scales have been carefully developed using the best available methods, and repeated evaluation over time indicates that they can be trusted across a range of exercise situations (3,4). Rigorous efforts in scale development have produced an imperfect but valuable tool, with estimates indicating that only 5% to 10% of exercisers do a relatively poor job of assessing their own effort using RPE (6). The general observation is that during aerobic exercise, stronger and more fit individuals tend to underrate intensity and that older or very inactive individuals tend to systematically overrate it (7,8). These realities make clear that practitioners should be mindful of how demographic variables may affect the quality and accuracy of RPE values provided by their patients, clients, and athletes.

It also is known that some exercisers may purposefully provide improper ratings of exertion in a way that is similar to false reporting that occurs in psychology and medical care. Specifically, exercisers “fake good” when reporting that intensity is lower than what it really feels to them, perhaps because they want to be viewed as particularly fit and especially when they want to impress others. Likewise, exercisers “fake bad” when reporting that intensity is greater than it actually feels, at least in part because they do not want to work at the prescribed intensity. In both cases, the lack of transparency on the part of the exerciser can interfere with the effective use of RPE for prescription of exercise. These actions are less likely when the exerciser trusts the exercise professional and understands the value of properly prescribed intensity on health and fitness outcomes. Therefore, practitioners are encouraged to develop a rapport with clients and patients that will facilitate accurate, authentic, and reproducible ratings.

Practitioners are encouraged to develop a rapport with clients and patients that will facilitate accurate and honest RPE ratings.

Also important for the implementation of RPE is making sure the exerciser is familiar with what RPE is and how it works. One option is to lead the exerciser through a preparticipation learning protocol that includes guidance on how exercisers should “anchor” perceptions of effort along a range from low to maximal intensity. This is an especially helpful procedure for novice or deconditioned individuals. These protocols also can include objectively measured exercise intensity (such as HR) in conjunction with RPE and provide the exerciser the opportunity to experience minimum exertion through moderate exertion all the way up to maximal exertion. Experiencing the full perceptual spectrum of exercise intensity allows future ratings to reflect the relative exercise intensity consistent with the predictions of Borg’s range model (3) (see anchoring sidebar). Ideally, the RPE learning protocol occurs before formally initiating an exercise program in a separate session, but a reasonable and practical approach is to integrate the learning procedures into a client’s first exercise session and to reinforce throughout subsequent exercise training sessions. Practitioners are encouraged to note that these recommendations will not always be feasible and should not serve as a barrier to the practitioner’s use of RPE. Based on the specific needs of the situation, a good recommendation in using RPE scales is to provide adequate instructions for the exerciser on how to conceptualize and estimate their exertion and the importance of accurate ratings (see instructions sidebar) (9).


Instructions: Pay close attention to how the exercise work rate feels. This feeling should reflect your total amount of exertion, combining all sensations and feelings of physical strain, effort, and fatigue. Do not concern yourself with any one body part or system and instead concentrate on your total feeling of exertion. Be as accurate as you can and use this scale, which ranges from 0, “extremely easy,” to 10, “extremely hard,” and includes depictions of how exertion might make someone feel.

Anchoring: Best practice for using RPE scales is to complete a graded exercise test allowing for the full range of exercise intensity from rest to maximal exertion, but practitioners can also provide anchoring for the scale by asking the client or patient to recall exercise experiences that would create a point of reference for what the range of exercise intensities feel like.


An important and valuable aspect of subjective effort ratings is that they allow the exerciser to self-adjust objective workload to account for any variable that might affect perceived effort so as to maintain the desired effort level. This process is known as autoregulation and is the ability and tendency of the exerciser to adjust actual intensity based on the circumstances of the moment (10). Given that RPE is an aggregate of many physiological and psychological influences, it changes in response to these variables and provides ongoing opportunities to adjust work level “on the fly” to meet training needs. As such, RPE as an autoregulatory tool can provide great value to practitioners because it acknowledges an individual’s tolerance for exercise based on a variety of interdependent factors. Exercise tolerance is affected by a multitude of factors, including hydration, nutrition, proper sleep, emotional state, prior exercise experience, and environmental considerations such as heat, humidity, and altitude. A great benefit of using RPE is that it is sensitive to these variables while remaining valid, reliable, and very user-friendly.


Dating back to Borg’s initial development of RPE as a concept, the primary way in which RPE has been used is during exercise “in the moment.” This in-task RPE is simply an “estimation” by the exerciser of their feelings of exertion while exercising (e.g., obtaining a rating at the end of each stage during an incremental exercise test). Innovations over time have diversified the timing of assessing exertion. A second application of RPE scales is when the exerciser uses exertion as a way to guide and regulate exercise intensity, something most often referred to as RPE “production.” During RPE production, exercisers adjust the external workload by manipulating running speed, treadmill incline, bike resistance, etc., to create a perceived internal level of effort corresponding to a prescribed RPE or range of RPE values. This approach is analogous to a prescribed HR training zone. For example, practitioners can prescribe an RPE production range (e.g., running intervals at an RPE 15–17) to guide effort level during training sessions. If a client has been using HR as a primary method for measuring exercise intensity, anchoring the training zones to the RPE production range within the exercise task could eventually reduce the need for HR monitoring during exercise sessions.

RPE scales also have been used at the conclusion of exercise in what is known as the session RPE (11). The objective of the session RPE is to allow the exerciser to estimate the effort associated with the overall load of the entire exercise bout, giving consideration to both intensity and duration. These session RPE values are then used to assess the effectiveness of a given session of exercise and also to plan, manage, and regulate overall training load to maximize adaptations and minimize the risk of overtraining. Session RPE is generally estimated several minutes after the termination of an exercise bout. The original approach was aimed at measuring exertion in aerobic activities such as running and cycling. However, RPE has become increasingly useful in quantifying workloads in resistance exercise and many other types of anaerobic training (12,13).

Using RPE, practitioners can prescribe and monitor resistance exercise intensity based on perceived exertion instead of using the more traditional percentage of one-repetition maximum (1RM). Conducting an accurate 1RM protocol may not be feasible in some settings and inappropriate for some populations (e.g., novice, older, or pregnant exercisers). Likewise, a 1RM performance is an absolute measure of strength at a given time and may not reflect current training levels. In addition, the 1RM does not easily adjust for fatigue from previous training sessions, client feedback, or training history. RPE can be used to guide the selection of workload for circuit weight training (12), explosive resistance training (13), and compound movements. RPE can easily be used to plan macrocycles and mesocycles in strength and conditioning periodization programs. Prescribing RPE values to a daily or weekly exercise programming schedule reduces the likelihood of overtraining in athletes (13). The underlying principles of using RPE apply across a wide range of exercise and sport-related tasks and practitioners are encouraged to consider any number of possible uses in efforts to help clients and patients execute their physical activity programs.


Although RPE is the oldest and most established method of considering the subjective intensity of exercise, several other approaches and tools have been developed that fit easily within programs to create exercise experiences that are safe and beneficial for health and fitness. Two specific approaches that have gained popularity are the Talk Test and mood-based exercise programming. The Talk Test is based on the premise that exercise intensity can be defined by how easy or hard it is to talk during exercise (14). Being able to speak comfortably indicates effort that is moderately intense, whereas being unable to speak while exercising indicates effort that is severe or near maximal. In between these two effort points of intensity is where speaking is labored and difficult but possible, and this range of intensity is often described as heavy or vigorous (15). These different ranges have been shown to align closely with both the ventilatory and the lactate thresholds, RPE values, and HR (15). Likewise, mood-based exercise programming recommends exercising at intensities and on specific modalities that create a positive mood state. In these approaches, exercisers are encouraged to try different types and intensities of exercise and to note whether those sessions of exercise are perceived as pleasant, neutral, or negative, and to pursue regular exercise experiences that “feel good” (16). The primary idea is that exercise intensity, modality, and environment should be manipulated to induce mood states that are positive. Noteworthy is that feeling good during exercise promotes exercise adherence, and these positive feelings are associated with RPE values in the moderate range (17). Figure 3 provides a visual representation of how objective and subjective tools link together across the range of exercise intensities. Practitioners might consider the use of one or both of these tools in combination with RPE as part of a larger effort to find methods and approaches with clients and patients that work well and contribute to the ultimate goal of developing and sustaining a physically active lifestyle. Additional details and resources for these two concepts are available on the ACSM’s Health & Fitness Journal® Web site.

Figure 3
Figure 3:
Objective and subjective exercise intensity ranges.


Participation in exercise provides immense benefits to metabolic, cardiovascular, and mental health. Engaging in exercise that is both healthful and safe is critical. Tools available to the practitioner to make the lives of their clients and patients better through exercise are numerous. A strong case can be made that no other tool available to the practitioner exceeds RPE in terms of its combination of convenience and overall utility. Using RPE in a number of traditional and innovative ways in the daily work of making people’s lives better is worthwhile and has the potential to positively affect the working relationship between practitioners and the people they serve.


Ratings of perceived exertion have a long history of use in the world of fitness and exercise science, and today’s clinician and practitioner use of these tools can provide great benefit. Traditional and innovative uses of RPE scales allow individuals to engage in exercise safely and to optimize physiological and psychological aspects of physical activity. RPE scales represent a simple yet effective and convenient way to guide exercise testing and prescription.


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Recommended Readings

Intensity of Physical Activity and the “Talk Test”: A Brief Review and Practical Application By Anthony L. Webster, B.Sc., M.Sc., Ph.D. and Susana Aznar-Laín, B.Sc., M.Sc., Ph.D.
    Affect-Based Exercise Prescription: An Idea Whose Time Has Come? By Matthew A. Ladwig, M.S.; Mark E. Hartman, M.S., M.A.; Panteleimon Ekkekakis, Ph.D., FACSM.

      Exertion; Effort; Exercise; Training; Prescription

      Copyright © 2020 by American College of Sports Medicine.