Download Role of Ratings of Perceived Exertion during Self

Sports Med
DOI 10.1007/s40279-015-0344-5
REVIEW ARTICLE
Role of Ratings of Perceived Exertion during Self-Paced Exercise:
What are We Actually Measuring?
Chris R. Abbiss1 • Jeremiah J. Peiffer2 • Romain Meeusen3,4 • Sabrina Skorski5,6
! Springer International Publishing Switzerland 2015
Abstract Ratings of perceived exertion (RPE) and effort
are considered extremely important in the regulation of
intensity during self-paced physical activity. While effort
and exertion are slightly different constructs, these terms
are often used interchangeably within the literature. The
development of perceptions of both effort and exertion is a
complicated process involving numerous neural processes
occurring in various regions within the brain. It is widely
accepted that perceptions of effort are highly dependent on
efferent copies of central drive which are sent from motor
to sensory regions of the brain. Additionally, it has been
suggested that perceptions of effort and exertion are integrated based on the balance between corollary discharge
and actual afferent feedback; however, the involvement of
peripheral afferent sensory feedback in the development of
such perceptions has been debated. As such, this review
examines the possible difference between effort and
& Chris R. Abbiss
[email protected]
1
Centre for Exercise and Sports Science Research, School
of Exercise and Health Sciences, Edith Cowan University,
270 Joondalup Drive, Joondalup, WA 6027, Australia
2
School of Psychology and Exercise Science, Murdoch
University, Murdoch, WA, Australia
3
Department of Human Physiology, Vrje Universiteit Brussel,
Brussels, Belgium
4
School of Public Health, Tropical Medicine and
Rehabilitation Sciences, James Cook University,
Townsville, QLD, Australia
5
Institute of Sports and Preventive Medicine,
Saarland University, Saarbrücken, Germany
6
UC Research Institute for Sport and Exercise,
University of Canberra, Canberra, ACT, Australia
exertion, and the implications of such differences in
understanding the role of such perceptions in the regulation
of pace during exercise.
Key Points
Rating of perceived exertion scales have been used
within the literature to assess both effort and
exertion, although evidence exists to suggest that
these are slightly different constructs.
It is plausible that the neural processes involved in
the development of perceptions of effort and exertion
differ.
Examination of the difference between effort and
exertion may aid in improving our understanding of
the role these perceptions have in the regulation of
pace during exercise.
1 Introduction
The distribution of speed or energy expenditure throughout
an exercise task is known as pacing and is extremely
important to overall performance. As a result, research
aimed at understanding the underpinning mechanisms
influencing the selection of pace during exercise has dramatically increased within recent years. From this research,
the regulation of intensity during exercise appears largely
regulated by complex relationships between the brain and
other physiological systems, with several models proposed
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to explain this phenomena, including the central governor
model [1], teloanticipatory theory [2], pacing awareness
model [3], psychobiological model [4, 5], the flush model
[6], perceptions-based model [7] and complex systems
model [8, 9]. Many of these models indicate that afferent
sensory feedback from various physiological systems is
received by the thalamus and regulated within the brain [1,
2, 5, 9]. This information, in addition to several other
factors such as knowledge of the task duration/distance
remaining, memory of past similar experiences, motivation
and mood [5, 10], is believed to be important in the regulation of pace.
Important aspects within many of the abovementioned
models include the participants’ perception of exertion,
perception of effort and the task demands [7, 11]. Indeed, it
has been suggested that exercise intensity is regulated
based on one’s perceived exertion in order to ensure that
‘catastrophic’ or ‘critical’ disturbances to homeostasis do
not occur [1, 2]. This is supported by the relatively stable
increase in perceived exertion that is typically observed
during high-intensity, self-paced exercise (i.e. a time trial)
[12, 13]. Indeed, it has been proposed that the product of
the momentary perceived exertion and the fraction of distance remaining (referred to as a hazard score) may provide
an indication of changes in intensity during self-paced
exercise [11]. Importantly, it has also been suggested that
one’s perception of effort is centrally derived and largely
unaffected by peripheral afferent sensory feedback; however, the role of afferent feedback in the regulation of
intensity during self-paced exercise has been debated [14–
16]. Such uncertainty may be associated with slight but
important differences between the terms effort and exertion
and the measurement tools used to assess an individual’s
perceptions during exercise. As such, the purpose of this
review was to (i) highlight possible issues associated with
the measurement of perceptions of effort and exertion; (ii)
outline the role of the brain in the development of such
perceptions; and (iii) provide suggestions for research to
better understand the role of such perceptions on the regulation of pace during exercise.
2 Monitoring Perceptions of Effort and Exertion
To date, a number of subjective tools have been developed
to determine a participants’ localized (i.e. chest, arms or
legs) or whole-body ratings of perceived exertion (RPE)
during exercise [17, 18]. The most common of these
include Borg’s 6–20 rating of perceived exertion scale, and
Borg’s CR-10 and CR-100 scales. Modifications of these
scales have also been developed to examine symptomatic
breathlessness (Modified Borg Dyspnoea Scale) or pain
during exercise [17]. These scales are very easy to use and
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as a result have been extremely valuable in understanding
the psychophysiological stress experienced by humans
during physical activity [18–20]. Regardless, the factors
that influence one’s RPE during exercise are extremely
complicated as RPE is believed to be influenced by
numerous factors, including effort, strain, pain, discomfort
and/or fatigue [2]. A higher RPE is typically associated
with increased physiological stress and fatigue. Indeed,
numerous studies have shown that significant physiological
perturbations, such as an increase in heart rate, ventilation,
oxygen consumption, and metabolic acidosis (decrease
pH), result in greater RPE [17, 21, 22]. Consequently, the
association between changes in RPE and physiological
status (i.e. oxygen consumption, heart rate) have been used
as evidence of the strong concurrent validity of the RPE
scale [17, 23, 24].
Clearly, RPE is an important variable in understanding
the psychophysiological stress experienced during a variety
of physical tasks; however, it is possible that administration
of RPE scales differs slightly among laboratories. Notably,
throughout the literature RPE has been referred to as perceived exertion and a perception or sense of effort [25].
Some studies have also alternated between the terms perceived exertion and perceived exhaustion [26]. However, it
has been proposed that the exertion, which may be associated with physical and physiological stress induced as a
result of exercise, is distinctly different from perceptions of
effort [27, 28]. Indeed, exertion has been defined as the
‘‘degree of heaviness and strain experienced in physical
work’’ [17], whereas effort may be defined as ‘the amount
of mental or physical energy being given to a task’. Confusion between these terms is even evident in the original
derivative of the RPE scale where in Borg’s manuscript
entitled Psychophysical Bases of Perceived Exertion it is
stated that ‘‘there is a great demand for perceptual effort in
order to better understand man at work’’ [18]. Later in the
manuscript, Borg states that ‘‘the individual’s perception of
exertion during physical work is interesting’’ and that in his
opinion ‘‘perceived exertion is the best indicator of the
degree of physical strain’’ [18]. Thirty-plus years on, this
confusion still exists, with the American College of Sports
Medicine current comment on perceived exertion stating
that RPE ‘‘is a psychophysiological scale, meaning it calls
on the mind and body to rate one’s perception of effort’’
[29]. Recently, it has also been suggested that ‘perceived
exertion’ is a conscious manifestation of the feelings of
effort produced by exercise [7, 30, 31].
Directions given to participants, or the precision of the
questions asked when implementing an RPE scale, could
influence the response given and as a result may have
considerable implications in understanding the psychophysiological stress during a task and the role of RPE in
the regulation of self-paced exercise. Indeed, it is important
Understanding Effort and Exertion
to consider the particular research question which RPE is
being used to assess when administering RPE scales.
Within sports science research RPE is often taken as a
secondary measure in order to vaguely describe one’s
sensations during exercise. As such, it is plausible that the
primary research measure, and ultimately the study design,
may influence one’s interpretation of the RPE scale and the
response given. While clear instructions are provided as to
how to deliver Borg’s RPE scales, these instructions may
not be ideal since they mention both exertion and effort
[17]. Furthermore, while the anchor points provided with
the scale (i.e. light, somewhat hard, maximal exertion) may
assist participants in understanding the purpose of the
scale, it is possible that the terminology used when
describing this or similar scales may influence the interpretation of the scale. Indeed, a recent study by Swart et al.
[27] has found that participants are able to distinguish
between physical perceived exertion (using a modified
Borg Scale) and task effort and awareness. Furthermore, it
was found in this study that there was dissociation between
these two variables when exercising at low or maximal (i.e.
all-out) intensities (Fig. 1). In agreement with these findings, we have also observed differences in the rate of
increase in perceptions of pain (% change = 6.9 ± 4.1),
exertion (16.4 ± 7.6) and effort (2.0 ± 2.2) during three
repeated maximal, high-intensity 4-min efforts (unpublished data). Furthermore, we have found that during single-leg cycling, perceived exertion may be lower but
perceptions of effort and pain are similar to double-leg
cycling [32]. Possible differences between effort and
exertion may also explain why many participants are
unable to reach maximal exertion during various exercise
tasks. For instance, while the Borg scale’s upper anchor is
20 (i.e. maximal exertion), the published criterion for the
determination of maximal aerobic capacity has been a
rating equal to or greater than 17–18 (i.e. very hard) [33].
Clearly therefore, a large proportion of participants who
complete a graded exertion test fail to reach maximal
exertion, despite participants being asked to exercise to
volitional exhaustion. However, it is plausible that if
exercise is limited by muscle strength, anaerobic energy
contribution or other similar factors, the participants’ effort
is maximal but exertion slightly lower. However, to date
few studies have used a number of these perceptual scales
concurrently during exercise [27, 32] and thus the difference, importance and relationship between these variables
is not entirely clear. Furthermore, the independent influence of each of these perceptions on pacing and performance during exercise is not known.
It is plausible that alterations in the contribution of
central and peripheral fatigue that occur during exercise
can influence the association between effort and exertion.
De Morree and Marcora [25] observed significantly higher
RPE values with a corresponding lower power output at the
beginning (minutes 1 and 3) of a 15-min cycling time trial
after a pre-exercising eccentric fatiguing protocol (100
drop-jumps). The authors state that maintaining the same
pace with fatigued locomotor muscles would have resulted
in higher RPE and premature exhaustion [25]; hence,
participants decide to reduce their pace so that the RPE
does not reach its maximum before the end of the trial.
Furthermore, when the capacity to produce force is
reduced, more effort than normal is required for the same
task [15]. However, in this study participants were given
standard instructions on how to rate their perception of
effort on Borg’s 6–20 RPE scale. As previously mentioned,
effort may be defined as ‘the amount of mental or physical
energy being given to a task’. Hence, it is plausible that the
higher RPE values observed were because participants
were, at least in part, rating the amount of mental and
physical energy they were investing in an attempt to
achieve a similar power output as in the non-fatigued
condition. In contrast, a recently published study analysing
the effects of accumulated short-term fatigue on performance and pacing during a 40-km cycling time trial
showed significantly lower power output during a time trial
in a fatigued state, yet no difference in corresponding RPE
values, when introducing RPE as a ‘‘degree of heaviness
and strain experienced in physical work’’ (perceived
exertion) [34]. Together, these findings highlight the possibility that either the type of fatigue induced (i.e. acute vs.
accumulated; local vs. multifaceted), or the terminology
used when describing the Borg RPE scale, may have
influenced the response given.
Language and/or translation of terms may be another
important issue responsible for some confusion over the
use of the terms effort and exertion. According to the
Oxford English Dictionary [35], exertion and effort are
synonyms. Furthermore, when searching translations for
both words, dictionaries of various languages (e.g. German,
Spanish, Italian, Portuguese, Dutch and Japanese) often
provide the same word for both ‘effort’ and ‘exertion’.
Taking this into account, it is plausible that authors may
use both terms interchangeably. In a broader sense, it may
be speculated that speakers with English as a second language use the RPE scale differently, depending on their
‘interpretation’ of the translated term. For example, the
German translation for effort and exertion is the same term
(‘Anstrengung’). Furthermore, depending on the context of
the term, ‘Anstrengung’ can be used with regard to the
degree of heaviness experienced or the degree of energy
given to a task. When reviewing manuscripts published by
German researchers, it appears that the explanation of
Borg’s RPE scale may be defined as an ‘‘expression of the
subjective feeling of the heaviness of a given work load or
intensity’’ [36]. Hence, several factors seem to influence
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Fig. 1 Linear relationship
between TEA and P-RPE during
a a progressive exercise test,
b 100-km time trial,
c submaximal ride at 70 % of
the power during the 100-km
time trial, and d intermittent
sprints. TEA task effort and
awareness, P-RPE physical
ratings of perceived exertion,
* indicates slope and intercepts
significantly different from both
a and b [p \ 0.001],
** indicates slope and intercepts
significantly different from
a and b [p \ 0.001].
Reproduced from Swart et al.
[27], with permission
the introduction and delivery of the RPE scale, especially
when translated into other languages, including (i) the
translation of the original definition; (ii) the ‘interpretation’
of the translated term; and (iii) the instructors’ and participants’ understanding of these terms.
3 Perceptions and the Brain
3.1 Neural Regulation of Perceptions
To fully understand the complex relationship between
exertion, effort and pacing, an appreciation of how such
perceptions are developed and regulated within the brain
is necessary. Indeed, the development of perceptions,
interpretation of language and sensations associated with
effort and exertion during exercise involve multiple
regions within the brain. The brain is an organ of communication. Neurons within the brain connect in networks
that communicate with each other to provide multiple
functions. This network organization is particularly evident with regard to cognition, which involves the participation of diverse brain areas, including parts of the
limbic system such as the hippocampus, amygdala, frontal
cortex, thalamus, etc. Multisensory integration in the
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brain deals with the processing of information from the
different sensory modalities, such as sight, sound, touch,
smell, self-motion and taste [37]. Multisensory integration
also deals with interaction of various sensory modalities
and how each sensory modality influences other processing [38]. Furthermore, during intensive exercise this
is made even more complicated by considerable disturbances to physiological homeostasis, creating the need for
considerable communication and computing within the
brain and with peripheral physiological systems. As such,
perceptions may reflect how the brain integrates and
categorizes the input signals resulting from various different stimuli.
Perceptions of effort and exertion are believed to be
closely related to activity within various areas of the motor
cortex, including the premotor and primary motor areas
[39]. Indeed, the well-accepted corollary discharge theory
postulates that an efference copy of the central motor
command is sent directly from motor to sensory areas of
the brain in order to assist in the generation of perceptions
associated with motor output (Fig. 2) [40–43]. As such, the
close relationship between RPE and muscle activity (i.e.
electromyography) during exercise is thought to be largely
influenced by a central feed-forward neurophysiological
mechanism whereby as motor unit recruitment and firing
Understanding Effort and Exertion
Fig. 2 Neural regulation of perceptions associated with motor drive.
An efference copy of the neural drive is sent from the motor to
sensory regions of the brain in order to develop a forward model of
predicted sensory feedback. This predicted sensory feedback is
compared with actual sensory feedback, resulting in a match or
mismatch, which alters the development of perceptions. Reproduced
from Bubic et al. [40], with permission
frequency increase, the number of efferent copies received
by sensory regions within the brain also increases [39, 44,
45]. This theory is supported by the relationship between
perceptions of effort or exertion and the increase in central
drive required to exercise at higher intensities and/or during periods of muscle weakening resulting from peripheral
fatigue [46] or partial paralysis [47, 48]. Indeed, we have
recently shown that elevated peripheral fatigue and a
concomitant increase in central drive is associated with an
increase in RPE during constant-load, high-intensity
cycling [46]. Furthermore, De Morree et al. [39] have also
recently observed an association between perceived effort
and the amplitude of the movement-related cortical
potential, which reflects activity within the premotor and
motor areas of the brain [49]. Based on this, the authors
suggested that perception of effort might arise from the
primary motor cortex [39]; however, the authors also
highlighted the possibility that perceived effort may be
associated with activity in neural centres upstream of the
primary motor cortex, and possibly even the motor cortex
[39, 50]. Due to their involvement in homeostatic control,
awareness [51], emotion, error detection, motivation and
pain [52], higher brain centres such as the insular cortex
and cingulate cortex are believed to be extremely important
in perceptions that are associated with physical activity
[30, 53, 54]. Supporting this, Fontes et al. [30] observed an
association between increased neuronal activity in the
posterior cingulate gyrus and precuneus and rating of
perceived exertion during cycling. Furthermore, an
increased activation of the right anterior insular cortex has
been documented with increased perceived exertion during
dynamic exercise [55, 56]. Interestingly, it has also been
found that increases in activation of regions within the
insular cortex and anterior cingulate cortex may be the
direct result of central command per se, and independent of
muscle metaboreflex activation or changes in blood pressure [56].
In addition to the efference copy, afferent information is
believed to be extremely important in the development of
perceptions of effort and exertion during exercise (Fig. 2)
[31, 47]. Indeed, it is believed that effort is associated with
not only corollary commands received by the sensory
cortex but also expected reafference arising from the motor
drive (Fig. 2) [40, 47]. Indeed, Luu et al. [47] showed that
by reducing muscle force using a neuromuscular blockade,
sensations of heaviness were reduced, presumably due to
reduced peripheral feedback associated with paralysis of
muscle spindle intrafusal fibres, since it was assumed that
motor command must have been elevated. Aligned with
this hypothesis, it has recently been proposed that exerciseinduced pain is an important contributing factor in the
regulation of work intensity and is thus important in pacing
during exercise [57]. It has been shown that an opioid
analgesic to selectively block the activity in ascending
sensory pathways results in elevated RPE during a 5-km
cycling time trial [58]. However, within this study,
impaired muscle afferent feedback was also associated
with altered central motor drive [58], and thus it remains
unclear whether an alteration in corollary command, rather
than changes in afferent feedback, was the dominant
mechanism responsible for altered RPE. Regardless, based
on the current literature it appears reasonable to suggest
that such regions of the brain are responsible for the integration of physiological afferent signals from the periphery
to promote emotional and conscious control of perceptual
stress during exercise [30]. Under such a hypothesis, perceptions of both effort and exertion are likely to be dictated
by not only the discrepancy or balance between predicted
and actual sensory feedback but also other complex psychological factors such as memory/prior experience of
similar exercise [2], motivation [8], positive and negative
affect [10] and awareness [2].
However, it should be noted that the aforementioned
blockade studies have examined sensations of heaviness
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[47] or perceived exertion [58, 59], and as a result the role
of afferent feedback in the regulation of sensations of effort
and performance is not entirely clear [14–16]. Due to the
slight differences in the definition and interpretation of
exertion and effort, it is plausible that the dominant cause
of such perceptions differs. Indeed, since effort is associated with ‘the amount of mental or physical energy being
given to a task’ it seems plausible that the efference copy
of central command is likely to be important. Conversely,
since exertion refers to the sensations associated with the
‘strain experienced during a physical task’, it is possible
that actual sensory feedback may have a greater influence
when integrated to develop such perceptions. Borg seems
to have shared this assumption in stating that ‘‘the overall
perceived exertion rating integrates various information,
including many signals elicited from the peripheral working muscles and joints, from the central cardiovascular and
respiratory functions, and from the central nervous systems. All these signals, perceptions, and experiences are
integrated into a configuration of perceived exertion’’ [18].
Highlighting the difference between effort and exertion to
participants when examining perceptual responses during
motor tasks may assist in better understanding the central
and peripheral origins of such perceptions and their role in
the regulation of fatigue during exercise.
3.2 Neurochemistry and Perceptions
Clearly, the development and regulation of sensations, such
as exertion or effort, involve complex processes within
motor, sensory and other regions of the brain. The interactions of these systems can be characterized by the different neurotransmitters that dictate and create the
communication between neurons in different brain regions
and neuronal pathways. As such, understanding the function of various neurotransmitters is important in understanding perceptions and their role during self-paced
exercise. There are several candidate neurotransmitters that
influence the neural functions outlined above (Sect. 3.1),
and it is clear that these neurotransmitter systems will work
‘in concert’ to establish the integration of all information
and information processing in the brain. Monoaminergic
neurons modulate a wide range of functions in the central
nervous system. Noradrenergic neurons are involved in
cardiovascular function, sleep and analgesic responses,
while dopaminergic neurons are linked with motor function
and motivation, and serotonergic activity is associated with
pain, fatigue, appetite and sleep [60]. Other transmitters,
such as adenosine, glutamate, gamma-butyric acid and
others, are also influenced by disturbances of homeostasis.
All are linked with limbic processing of signals and will
crosstalk during exercise [61]. The influence of neurotransmitters in the integration of signals within the brain is
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likely to be especially important during intensive and/or
long-duration exercise. Indeed, it has been found that even
acute exercise increases the release of neurotransmitters in
several brain areas [61]. Our recent research showed that
not only climatic stress but also pharmacological manipulation of the neurotransmitters has the ability to cause
changes in endurance performance [62]. Furthermore, it
has been found that such pharmacological manipulation
alters pacing, specifically in the early phases of an exercise
task [63]. For instance, manipulations of serotonin, especially noradrenaline, result in a decrease in power output
during the early stages of a time trial. However, dopamine
reuptake inhibition has the opposite effect and subjects are
able to maintain a higher power output compared with
placebo. When neurotransmission is manipulated through a
selective serotonin reuptake inhibitor, subjects are often
unable to perform an end sprint, indicating an absence of a
reserve capacity or motivation to increase power output
[62].
Although pacing and/or overall performance may be
altered when neurotransmitters are manipulated, typically
no differences in perceived exertion or thermal stress are
observed when compared with placebo trials [64–67]. It
has been proposed that participants continuously modify
their pace in order to match the momentary perceived
exertion with the expected level of exertion at a given point
during an exercise task [11]. As such, drugs acting to
enhance brain dopamine would change the initial anticipatory setting of work rate by elevating arousal and motivational levels. Under such circumstances, perceived
exertion may be reduced, resulting in a mismatch between
the actual and template perceived exertion. Consequently,
this would lead to an increased work rate and heat production, until the conscious perceived exertion returns to
anticipated levels. In contrast to dopamine, an increase in
brain noradrenaline concentration has detrimental effects
on power output and thus exercise performance. Despite
the lower power output when manipulating the noradrenergic system, perceived exertion between conditions has
been shown to be similar [62].
Taken together, it appears that performance-enhancing
or -retarding effects of central nervous system drugs on
endurance performance are reflected by changes in the
distribution of pace during exercise. In the presence of
larger climatic stress, subjects seem to adapt their strategy
specifically in the earlier phases of exercise. Such alterations in exercise intensity may be in order to ensure
exercise is performed at a given level of perceived exertion
(i.e. the RPE template). Indeed, perceived exertion is typically not influenced by the drug treatments outlined above,
indicating that subjects maintain the same level of exertion,
regardless of the power output produced or the core temperature achieved. Nonetheless, to date the majority of
Understanding Effort and Exertion
studies that have examined the association between pacing
and neurochemistry have examined perceptions of exertion
and thermal sensation, rather than perceived effort. Similar
manipulation trials may be valuable in better understanding
the relationship between pacing or exercise performance
and various perceptions, including both effort and exertion.
4 Future Research that May Aid in Better
Understanding the Role of Ratings of Perceived
Exertion in Pacing
Many of the issues outlined in this review centre on the
inconsistent use of the terms exertion and effort. We have
highlighted not only possible neurological differences in
the way individuals perceive exertion and effort but also
issues with the explanation of the perceived exertion scale.
Specifically, the instruction provided, or questions asked,
when implementing the scale are likely to influence the
measured outcomes. To address this issue, studies designed
to independently assess both effort and exertion are needed.
Such work should build on that of Swart et al. [27] and
examine the influence of an individual’s ability to distinctively differentiate exertion and effort. Given that there
is evidence for dissociation between perceptions of effort
and exertion during exercise of varying intensity [27] or
total muscle recruitment [32], it may be interesting to
conduct such research during various modes of exercise.
Indeed, manipulation of factors such as the level of
eccentric loading, exercise intensity, task familiarity or
external mental requirements may alter the association
between effort and exertion during physical activity.
Although extremely complicated, these studies should also
focus on the mechanisms and neural process responsible
for changes in perceived exertion and effort during exercise. Examination of regional brain activity (i.e. functional
magnetic resonance imaging, electroencephalography or
cerebral blood flow) or alterations in neural function (i.e.
manipulation of neurotransmitters or direct current stimulation) may assist in better understanding the neural process responsible for the development of perceptions during
exercise.
Physiological disruptions to homeostasis associated with
the onset of fatigue appear to influence an individual’s
perception of exertion and effort [39, 46]. Therefore,
examining the association between varying models or
causes of fatigue (i.e. severity, central/mental vs. peripheral) will certainly assist in our understanding of the role of
such perception in sport and exercise performance. Such
research could incorporate many physiological or psychological manipulations that are known to alter fatigue
development (i.e. hypoxia, hyperthermia, physical fatigue,
pharmacological administration, deception/placebo, or
mental fatigue), which could assist in better understanding
possible differences between perceptions of effort and
exertion and their role in pacing, fatigue and performance.
Previous experience and memory is believed to be
important in the complex integration of the various factors
that are ultimately responsible for the perception of effort
and exertion [2]. Therefore, an individual’s level of
expertise could significantly influence the sensitivity of
such measures. Research aimed at examining the sensitivity of perception of effort or exertion across a continuum
of ages and fitness levels would provide much-needed
information in this area. During such research, consideration should also be given to the sensitivity of the scales
used. Indeed, different scales of varying sensitivity (i.e.
6–20, 1–10 or 0–100), and utilizing different anchor points
or descriptions, have been developed to monitor perceptions during exercise. As described in Sect. 2, one’s
interpretation of any given perceptual scale is likely to
depend on the anchor points or terminology used. As such,
research examining these anchors in order to determine the
most appropriate terminology for various perceptions is
warranted. In addition, examination of the Borg scale in
comparison to more flexible visual analogue scales could
provide insight into this area. However, it should also be
noted that since the descriptions and values within a given
scale will influence the precise outcome given, the comparison of information across scales is extremely complicated. This has implications in the examination of possible
differences and relationships between such perceptions.
5 Conclusions
This review highlights the possible differences between
perceptions of effort and exertion. To date, few studies
have examined numerous perceptions during exercise, and
thus the potential difference, importance and relationship
between these variables is not well understood. It appears
that perceptions of both exertion and effort are regulated
within various regions of the brain based on the integration
of information relating to motor drive, afferent feedback
and numerous other factors, including prior experience,
awareness and motivation. In particular, perceptions of
effort may be largely influenced by an efference copy of
central motor command which is sent from motor to sensory regions of the brain. Conversely, perceptions of
exertion during exercise may be influenced, at least in part,
by alterations in afferent feedback associated with disturbances to homeostasis. The relative contributions of
afferent feedback, efference copy of motor drive and the
integration of this information in the generation of such
perceptions is not yet fully understood. Since effort and
exertion are both likely to be extremely important in
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understanding the underpinning mechanisms influencing
the selection of pace, further research monitoring both of
these variables during exercise is warranted. Such work
may aid in better understanding the complex neural processes that are important in fatigue development and pacing, and during exercise.
Compliance with Ethics Standards No sources of funding were
used to assist in the preparation of this review. Chris R. Abbiss,
Jeremiah J. Peiffer, Romain Meeusen and Sabrina Skorski have no
conflicts of interest relating to the contents of this review.
17.
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