13.2: Monitoring Perceptions of Effort and Exertion

13.2.1. Measurement Scales

The most common instrument used to measure perceived exertion is Borg’s RPE scale (Borg 1982; 1998). This 15-point scale ranges from 6 (no exertion at all) to 20 (maximal exertion), with intermediate points anchored to verbal expressions of effort such as very light, somewhat hard, and “very hard”. The 6–20 scale was designed to parallel the heart rate (HR) range of a normal healthy male (i.e., 60–200 beats/min). Initial efforts to validate the RPE scale yielded a correlation of 0.85 between the RPE and HR (Borg, 1962). However, subsequent studies have produced a wide range of correlation coefficients for a variety of tasks and participants (Chen et al., 2002). An alternative to the 15-point RPE scale is the category-ratio (CR-10) RPE scale (Borg, 1982). This scale has a primary numerical range of 0 to 10, although a maximum intensity greater than 10 can be selected using free magnitude estimation (see Borg, 1998). The CR-10 is a general intensity scale that can be used in a variety of settings to assess other sensory perceptions, including pain, dyspnea, and ergonomic fatigue (Borg, 1998).

Alternative RPE scales to those authored by Borg have been developed and may be more appropriate for specific settings or populations. These include an RPE scale based on ”repetitions in reserve” for use during resistance training (Zourdos et al., 2016), the Session RPE Scale used in the calculation of athlete training load (Foster et al., 2001), and a variety of pictorial scales designed for use in pediatric populations (e.g., Utter et al., 2002). Buckley et al. (2000) have also validated a braille version of Borg’s standard 6–20 RPE scale for individuals with visual impairment.

Differentiated RPE scales have been used to distinguish between the central (cardiopulmonary) and peripheral (muscle and joint) factors contributing to an individual’s RPE. Knowledge of differentiated RPE allows for greater understanding of the relative influence of central and peripheral signals of exertion to the overall RPE value (Hutchinson & Tenenbaum, 2019). The Task Effort and Awareness (TEA) scale (Swart at al., 2012) differentiates perceived exertion from task effort, which is defined as “the conscious mental (psychic) effort required to sustain or increase the current exercise intensity” (Swart at al., 2012, p. 42). Studies using the TEA scale have been able to shed light on the distinct contributions of perceived effort and the physical symptoms induced by exercise (i.e., perceived exertion) to the regulation of exercise intensity (e.g., Venhorst et al., 2018).

13.2.2. Scale Administration

Just as terminology has been used somewhat loosely and interchangeably, RPE scales have been used to assess both effort and exertion as well as related concepts such as fatigue and discomfort (Hutchinson & Tenenbaum, 2019). It is of critical importance that researchers distinguish between measures aimed at evaluating an internal sense of effort versus a perception of peripheral discomfort or exertion, and/or an integrated sum of all signals (Christian et al., 2014). Careful consideration should be given to the specific definitions provided to participants and the nature and precision of the questions asked when implementing an RPE scale. Furthermore, established principles of administration must be carefully followed to ensure the validity and reliability of the measure. These include clear and comprehensive instructions regarding the use of the scale (see Razonet al., 2012) and an opportunity for scale users to ask clarifying questions and to practice making perceptual estimates. A familiarization or learning trial is recommended prior to either rating, or prescribing, exercise intensity with RPE (Pageaux, 2016).

13.2.3. Estimation and Production Mode

In exercise settings, RPE is usually used in one of two modes: estimation and production. When used in estimation mode the client/patient provides an RPE during a prescribed exercise intensity. For example, when exercising at a given percentage of maximal HR, or during a graded exercise test. When used in production mode individuals are asked to produce and maintain an exercise intensity corresponding to a target RPE (e.g., moderate intensity exercise is prescribed at 12–13 on the Borg 6–20 scale; Garber et al., 2011). The production paradigm provides an alternative method by which to prescribe exercise intensity, instead of relying on a certain percentage of maximal heart rate or oxygen uptake. This is particularly useful in settings such as cardiac rehabilitation where patients may be taking HR lowering medications such as beta-blockers. In the assessment ofcardiorespiratory fitness, maximal oxygen uptake (VO₂ max) can be predicted from the linear relationship between submaximal RPE and oxygen uptake. This method has been found to be valid and reliable across a number of populations and exercise modalities (Coquart et al., 2014).