13.1: Defining the Concept

The terms effort and exertion are often used interchangeably, although they are different (but related) constructs. The term perceived exertion was first introduced by Swedish psychophysicist Gunnar Borg in the 1960s as subjective complement to the objective responses (e.g., heart rate, and force production) observed during exercise. Borg defined exertion as the “degree of heaviness and strain experienced in physical work” (Borg, 1998, p. 8) and developed a scale to measure this concept, known as the Rating of Perceived Exertion (RPE) scale. Borg conceptualized perceived exertion as a configuration of sensations stemming from the peripheral muscles, cardiopulmonary system, and other sensory organs and cues. Included within this conceptualization are psychological constructs such as motivation and affect that are viewed as an integral part of the experience of exertion. The notion of discomfort and/or fatigue was also added to later definitions of perceived exertion. Drawing from Borg’s original definition, Robertson and Noble (1997) defined perceived exertion as “the subjective intensity of effort, strain, discomfort, and/or fatigue that is experienced during physical exercise” (p.407). Although this definition is widely accepted within the field of exercise science, it is problematic in that it brings together a number of distinct concepts; concepts that are rated differently when adequately defined, such as effort and discomfort (Steele et al., 2016) or exertion and fatigue (Micklewright et al., 2017). As a result, several authors have stressed the need for greater precision in the study of perceptual responses during physical activity(e.g., Hutchinson & Tenenbaum, 2006). Specifically, it is argued that the sense of effort is distinct from other sensations experienced during exercise¹ (Abbiss et al.,2015; Pageaux, 2016; Smirmaul, 2012).

Effort perception (or the sense of effort) refers to the cognitive feeling of work associated with voluntary actions (Preston & Wegner, 2009). In an exercise context, perceived effort has been operationally defined as “the amount of mental or physical energy being given to a task” (Abbiss et al., 2015, p. 1237). In contrast to perceptions of exertion, which rely upon the integration of sensory information transmitted from the body to the brain during exercise, the sense of effort is believed to be centrally generated (by the brain) with little to no influence from afferent feedback (Marcora, 2009; 2010). See Figure 13.1. To understand this idea, consider that a voluntary action is always carried out with a certain amount of effort, in the sense that each time a motor command is initiated, or even simulated, certain mechanisms in the brain need to determine the strength of this command (Lafargue & Franck, 2008). In essence, how hard one perceives themselves to be trying at a particular task is the subjective experience of effort. Researchers have used anesthesia to block or attenuate sensory feedback during a physical task in order to demonstrate that the sense of effort is independent of afferent feedback (e.g., Marcora, 2009) although this has been a topic of some debate (e.g., Eston, 2009).

Figure 13.1. Conceptual Diagram of the Origins of Perceived Effort and Exertion

Note. Voluntary movements are produced by sending motor commands from the brain to the muscles via motor descending pathways, with an “efference copy” being concomitantly delivered to sensory brain areas. This neural representation forms the basis of perceived effort. The result of the movement is feedback from sensory receptors in the peripheral nervous system, transmitted via ascending pathways to the brain. The brain then organizes this information and makes sense of this information (thus distinguishing perception from sensation) resulting in perceived exertion. Artwork in Figure 13.1 credited to Servier Medical Art by Servier under a Creative Commons Attribution License (CC-BY). Figure 13.1 is adapted from Muramatsu, K. (2020). Diabetes mellitus-related dysfunction of the motor system. International Journal of Molecular Sciences, 21(20), 7485, https://doi.org/10.3390/ijms21207485 under a Creative Commons Attribution License (CC-BY).

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Reference

¹ Smirmaul (2012) has offered a useful example for distinguishing effort from exertion. Imagine a cyclist who, after a tough uphill climb, begins a downhill section and stops pedaling, coasting downhill solely by momentum. This cyclist will still be feeling strong sensations of discomfort associated with the uphill climb (perceived exertion), but the effort expended to coast downhill is virtually zero, resulting in low perceived effort.