ESTIMATION OF RESISTANCE EXERCISE INTENSITY USING THE OMNI
RESISTANCE EXERCISE SCALE (OMNI-RES)
The purpose of this study was to evaluate ratings of perceived exertion (RPE)
from the OMNI-RES and muscle activity responses during the knee extension and chest
press resistance exercises performed at six relative exercise intensities.
Twenty recreationally trained women between the ages of 18 and 30 years
volunteered to perform the chest press and leg extension exercises at 40%, 50%, 60%,
70%, 80%, and 90% of their 1-repetition maximum (1-RM). RPE and EMG were
measured during all intensities.
Perceived exertion responses to the six resistance exercise intensities were
examined separately for the chest press and the knee extension exercises using a one-way
repeated-measures analysis of variance (ANOVA). These analyses revealed significant
(P<0.001) Intensity main effects for both exercises. A significant intensity main effect
for EMG was found for the vastus medialis. No significant Intensity main effect was
found for the pectoralis major or triceps muscles.
These results showed that RPE from the OMNI-RES increased as intensity (%1RM) increased, which supports the concurrent validity of the OMNI-RES.
1
ESTIMATION OF RESISTANCE EXERCISE INTENSITY USING THE OMNI
RESISTANCE EXERCISE SCALE (OMNI-RES)
Introduction
The OMNI-Resistance Exercise Scale (OMNI-RES) is used to measure ratings of
perceived exertion (RPE) during resistance exercise. This scale differs from other RPE
scales in that it has mode specific pictorial descriptors. The OMNI-RES is designed to
have broadly generalizable properties, meaning that it is widely applicable to different
types of individuals and to different types of activities. Robertson et al. (19) validated the
OMNI-RES by demonstrating a linear relation between RPE and both total weight and
blood [Hla] during resistance exercise. Correlation coefficients between RPE and blood
[Hla] were .87 and correlation coefficients between RPE and total weight were .79 to .91.
These results establish the concurrent validity of the OMNI-RES during resistance
exercise using blood [Hla] as the physiological criterion variable.
The link between blood [Hla], total work, and RPE from the OMNI-RES agrees
with Borg’s model of the Effort Continua. This model holds that perceived exertion
responses during dynamic exercise are related to physiological responses (2). The
interdependence between perceptual and physiological responses during dynamic
exercise performance provides a rationale for the utilization of RPE in exercise testing
and prescription. This rationale is extrapolated from Borg’s concept that the subjective
2
response to an exercise stimulus involves three main effort continua: physiological,
perceptual, and performance (2,18). The link between the three continua indicates that
perceived exertion responses provide similar information about exercise performance as
do a number of physiological responses during dynamic aerobic and resistance exercise.
Identifying the physiological responses underlying RPE provides a greater
understanding of perception during exercise and increases the applicability of perceived
exertion scales. For the OMNI-RES, blood [Hla] and total work have been identified as
physiological responses that mediate RPE during resistance exercise (19). Previous
research using the Borg RPE scale and the category-ratio (CR-10) scale to measure
perceived exertion has identified muscle activity and relative exercise intensity as
potential mediators of RPE (8,10,6,17).
A number of studies have found that RPE increases as the % 1-RM lifted
increases (8,9,15,20). For instance, Suminski et al. (20) examined RPE-Overall during
ten repetitions of seven exercises performed at 50% and 70% 1-RM. RPE was higher at
70% than at 50% for all seven exercises. The relation between RPE and % 1-RM is
strengthened when total work is held constant, which eliminates the possibility that RPE
responses are dependent on the amount of work performed. Lagally et al. (9) assessed
RPE during seven exercises at 30% and 90% 1-RM. Subjects performed fifteen
repetitions at 30% 1-RM and five repetitions at 90% 1-RM. The results indicated that for
all seven exercises there were uniform increases in RPE in response to increases in
intensity with total work held constant. The results of these studies indicate that RPE
increases systematically as resistance exercise intensity increases, independent of total
work performed.
3
Electromyography (EMG) measures the intrinsic activity of muscle. Lagally et al.
demonstrated a relation between EMG and RPE from the Borg 15-Category scale during
the bench press performed at 60% and 80% 1-RM (10) and the biceps curl performed at
30%, 60%, and 90% 1-RM (8). Using the CR-10 scale to assess perceived exertion,
Pincivero et al. (17) demonstrated a similar relation between EMG and RPE during a
sustained isometric contraction equivalent to 80% MVC held to the point of failure.
Hasson et al. (6) also reported high correlations (r = .89 and .96) between RPE and EMG
from the CR-10 scale during sustained isometric exercise.
Muscle activity likely mediates perceived exertion through a neuromuscular
feedforward mechanism (8). The theory of the feedforward mechanism holds that when
the motor cortex sends efferent messages to the muscles to activate, it sends corollary
signals to the sensory cortex (3), where the perception of exertion is regulated.
Therefore, as muscle activity increases, an increase in the number of corollary commands
received by the sensory cortex causes the exertional sensations to be intensified. Thus,
corresponding increases in EMG and RPE would suggest that these two variables may be
functionally related (8). The relation between muscle activity and perceived exertion
responses from the OMNI-RES has not yet been examined.
The purpose of this study was to evaluate ratings of perceived exertion (RPE)
from the OMNI-RES and muscle activity responses during the knee extension and chest
press resistance exercises performed at six relative exercise intensities. It was
hypothesized that as exercise intensity increased, OMNI-RPE and muscle activity would
demonstrate corresponding increases.
4
Methods
Subjects. Twenty recreationally trained women between the ages of 18 and 30
years voluntarily participated in this cross-sectional investigation. Subject characteristics
are shown in Table 1. Subjects were recruited from Kinesiology and Recreation classes
at Illinois State University. All individuals reported that they were free of skeletal,
muscular, cardiovascular, or endocrine disorders that would preclude exercise testing.
Each participant completed a medical history questionnaire and provided their written
consent to participate. The Institutional Review Board of Illinois State University
approved all procedures used in this investigation.
Orientation Session. The study was conducted over two sessions. The first
served as an orientation session. During the orientation session height, weight and body
composition were measured for each subject. Body density was estimated via skinfolds,
with percent body fat predicted from three sites according to the procedures of Jackson
and Pollock (7). Also during the orientation session, a one-repetition maximum (1-RM)
was established for the chest press exercise and knee extension exercise on the Nautilus
machines using the method of Lombardi (11). One-repetition maximum procedures
involved adding progressive resistance until subjects could complete only one repetition
with good form. The 1-RM values were used to set the six intensities (40% through
90%) during the experimental session. Two and a half and five pound weight plates
ensured that the weight lifted was as close as possible to a specified percentage. The
chest press and knee extension exercises were performed using Nautilus variable
resistance machines. Only the right leg was used for the knee extension exercise. The
5
weight stacks of each resistance exercise machine were covered so the subjects were
unaware of the weight they were lifting. Instructions and anchoring procedures for the
OMNI-RES were administered prior to the 1-RM procedures during this session.
Experimental Session. Each subject participated in an experimental session that
was at least 48 hours but no more than 168 hours after the orientation session. A warmup consisting of 10 repetitions at 20% 1-RM was performed immediately prior to the
experimental testing. Each subject was randomly assigned to an experimental sequence
that included six resistance exercise intensities set at 40%, 50%, 60%, 70%, 80%, and
90% 1-RM. Subjects performed one repetition of the exercise at a given intensity and
gave an active muscle rating of perceived exertion after each repetition. Muscle activity
was collected during all repetitions. Subjects were instructed to perform each lift to a 2count up, 2-count down cadence set by a metronome at 70 beats∙min. Cadence was
controlled in order to allow RPE and EMG comparisons between each of the intensities.
Perceived Exertion Assessment Procedures. RPE was provided following each
repetition using the OMNI-RES (19) at each intensity. A rating specific to the active
muscles (RPE-AM) was estimated at the end of the repetition. The OMNI-RES was in
clear view of the subject at all times. Scaling instructions were read to each subject
during the orientation session, and each subject was asked to re-read the scaling
instructions prior to the warm-up in the experimental session. Scaling instructions
included a definition of perceived exertion, an explanation of active muscle ratings, an
explanation of the use of the scale, and a chance to ask questions. During the 1-RM
procedures, rating scale anchors were established by having each subject perform an
unweighted repetition and a 1-RM using the chest press and knee extension exercises.
6
The feelings of exertion in the active muscles (triceps, chest, quadriceps) during the
unweighted repetition were assigned a 0 or “extremetly easy” on the OMNI scale and the
feelings of exertion in the active muscles during the 1-RM were assigned a 10 or
“extremely hard” on the OMNI scale.
Electromyography Assessment Procedures. Muscle activity was assessed
using the MP100 EMG System (Biopac Systems, Inc., Santa Barbara, CA). The EMG
signals were monitored using EL 500 Series disposable surface electrodes. Two
disposable surface electrodes (EL 500 Series) were placed 2 cm apart over the belly of
the pectoralis major, triceps brachii, and vastus medialis. Electrode sites were cleaned
with alcohol prior to electrode placement. All electrodes remained in place until data
were collected in all intensities. The EMG signals were differentially amplified using
gains between 500 and 5000, with an EMG 100B electromyogram amplifier module
(Biopac). The amplifiers had a differential input impedance of 2 megaohms and a
common mode input impedance of 1000 megaohms, with a common mode rejection ratio
of 110 dB. Amplifiers were set with a low-frequency cutoff of 3 Hz and a highfrequency cutoff of 10 Hz, each with single-pole roll-off filters to minimize the effects of
noise (MP100, Biopac). To identify the descent and ascent phases of each repetition, a
TSD130B series goniometer (Biopac) was placed on the lateral surface of the elbow and
the knee to monitor joint flexion and extension.
An isometric reference position (IRP) was used in order to normalize the EMG
data. To perform the IRP for the chest press exercise, the spotter assisted the subject in
adjusting her 80% 1-RM load until the elbows reached 90 of flexion. Once the desired
angle was reached, the spotter released the weight and the subject held the weight steady
7
for 7 seconds while the EMG data were collected. To perform the IRP for the knee
extension exercise, the spotter assisted the subject in adjusting her 80% 1-RM load until
the knee reached 45˚ of flexion. Once the desired angle was reached, the spotter released
the weight and the subject held the weight steady for 7 seconds while the EMG data were
collected. The IRP data were collected before the first intensity, after the third intensity
and after the sixth intensity. The mean value of the third second of the three IRP trials
was calculated for use in normalizing the data collected during the six 1-RM intensities.
All EMG data collected from the six 1-RM intensity repetitions were subsequently
expressed as a percentage of isometric reference position (%IRP) and used in the
analyses.
Statistical Analysis. Perceived exertion responses to the six resistance exercise
intensities were examined separately for the chest press and the knee extension exercises
using a one-way repeated-measures analysis of variance (ANOVA). Post hoc analyses
(paired t-tests) were performed to probe a significant Intensity main effect. The alpha
level was adjusted using the Bonferroni adjustment (0.05/5 = 0.01).
For the chest press exercise, EMG data were collected from the pectoralis major
and triceps muscles. For the knee extension exercise, EMG data were collected from the
vastus medialis. The main EMG responses from each of these muscles during each of the
six intensities were treated with separate one-factor, repeated-measures ANOVAs. Post
hoc analyses using paired t-tests were performed to examine differences in EMG between
the six resistance exercise intensities. The alpha level was adjusted using the Bonferroni
adjustment (0.05/5 = 0.01). Only the EMG from the concentric phase of each exercise
was used in the analysis. A P value of 0.05 was used to establish statistical significance.
8
All analyses were performed using the Statistical Package for the Social Sciences (SPSS,
Inc., Chicago, IL).
Results
Results of the one-way repeated-measures ANOVAs performed to examine
perceived exertion responses for the chest press and knee extension exercises indicated a
significant (P = 0.001) main effect for Intensity. Paired t-tests with the alpha adjusted
using the Bonferonni procedure (0.05/5 = 0.01) were performed to further explore the
Intensity main effect. Only differences between adjacent intensities for the chest press
and knee extension were examined. For the chest press, these analyses indicated that
RPE increased significantly (P<0.007) as exercise intensity increased, although at the P<
0.01 level, RPE between 80% and 90% 1-RM was not significantly different. For the
knee extension, RPE increased significantly (P<0.001) as intensity increased from 40% to
90% 1-RM. Means and standard deviations for perceived exertion at each intensity for
both exercises are shown in Table 2.
Complete EMG data were obtained on 16 subjects. Five subjects had missing or
incomplete EMG data because of instrument artifact and were not included in the
analyses. Means + standard deviations for EMG from the concentric phase of each
repetition of the chest press and knee extension exercises are shown in Table 3. There
was no significant intensity main effect for the pectoralis major or triceps muscles. The
analyses revealed a significant (P = 0.001) intensity main effect for EMG for the vastus
medialis. For the vastus medialis, post-hoc analyses using paired t-tests with the alpha
adjusted using the Bonferonni procedure (0.05/5 = 0.01) indicated that muscle activity
was significantly different (P = 0.006) between 60% and 70% 1-RM.
9
Discussion
It was hypothesized that muscle activity and relative exercise intensity (i.e. % 1RM) could play a role in the estimation of perceived exertion from the OMNI-RES. It
was the intent of the present investigation to demonstrate a link between these variables
and RPE responses during the chest press and knee extension exercises. The results
indicate that RPE increased as intensity increased from 40% 1-RM to 90% 1-RM. These
results are consistent with the results from numerous previous studies. For instance,
Lagally et al. (10) found that active muscle RPE increased as resistance exercise intensity
increased from 60% 1-RM to 80% 1-RM during the bench press exercise. Suminski et al.
(20) also found that an increase in exercise intensity from 50% to 70% 1-RM
corresponded with a significant increase in RPE during seven different resistance
exercises. Similarly, Lagally et al. (9) found that as 1-RM increased from 30% to 90%,
RPE increased for seven different resistance exercises.
The EMG results indicated no significant differences across intensity for any of
the three muscles examined, with the exception of the vastus medialis at 60% and 70% 1RM. Considering that numerous studies (1,8,10,12) have demonstrated that muscle
activity (i.e. EMG) increases as dynamic exercise intensity increases, our results are
surprising. The fact that EMG was not different even when compared between the
lightest and heaviest intensities (i.e. 40% and 90% 1-RM) suggests that experimental
design was not suitable for assessing changes in muscle activity. For example, a single
repetition (lasting 4 seconds) at each intensity may not be enough of a stimulus to
produce significant (measurable) differences in muscle activity. In previous studies that
examined EMG and RPE during dynamic resistance exercise and used surface EMG data
10
collection, the minimum amount of exercise performed for EMG data collection was 20
seconds of knee extension exercise (5) or three repetitions of knee extension (16). Both
of these investigations demonstrated corresponding increases in EMG and RPE as
exercise intensity increased. Thus, our one-repetition experimental design, which was
used to allow inclusion of multiple intensities without undue fatigue, may have limited
our ability to detect significant differences in muscle activity. Future studies should
examine EMG during sets of multiple repetitions performed at various intensities.
Unfortunately, our limited EMG results cannot be used to support our hypothesis
that EMG and RPE from the OMNI-RES would be related during resistance exercise.
However, given previous research, it is likely that a relationship does exist between EMG
and RPE, but it went undetected in the present study because of limitations in the
methods. In spite of the lack of significance in the EMG results, the results of this
investigation demonstrate that OMNI-RES RPE is sensitive to changes in exercise
intensity and thus is an appropriate method of regulating resistance exercise intensity.
In order to further investigate the applicability of the OMNI-RES, future studies
might compare novice and highly trained lifters with recreationally-trained lifters. It is
possible that individuals with less or more resistance training experience compared to
recreationally-trained lifters may report exertion differently using the OMNI-RES. In
addition, studies employing estimation-production paradigms would be useful for further
validating the use of OMNI-RES RPE as a method of prescribing RPE intensity during
training. These paradigms would help to demonstrate whether or not OMNI-RES RPE
can be used to help individuals select appropriate resistance exercise intensities during
training sessions.
11
References
1. BIGLAND, B. and O. C. J. LIPPOLD. The relation between force, velocity, and
integrated electrical activity in human muscles. J. of Physiology. 123: 214-224,
1954.
2. BORG, G. Perceived exertion as an indicator of somatic stress. Scand. J. Rehabil.
Med. 2: 92-98, 1970.
3. CAFARELLI, E. Peripheral contributions to the perception of effort. Med. Sci.
Sports Exerc. 14: 382-389, 1982.
4. GAMBERALE, F. Perceived exertion, heart rate, oxygen uptake and blood lactate
in different work operation. Ergonomics. 15: 545-554, 1972.
5. GARCIN, M., J. F. VAUTIER, H. VANDEWALLE, and H. MONOD. Ratings of
perceived exertion (RPE) as an index of aerobic endurance during local and
general exercises. Ergonomics. 41: 1105-1114, 1998.
6. HASSON, S. M., J. H. WILLIAMS, and J. F. SIGNORILE. Fatigue-induced
changes in myoelectric signal characteristics and perceived exertion. Can. J. Sport
Sci. 14: 99-102, 1989.
7. JACKSON, A. S. and M. L. POLLOCK. Practical Assessment of body
composition. Physician and Sports Medicine. 13: 76-90, 1985.
8. LAGALLY, K. M., R. J. ROBERTSON, K. I. GALLAGHER, et al. Perceived
exertion, electromyography, and blood lactate during acute bouts of resistance
exercise. Med. Sci. Sports Exerc. 34: 552-559, 2002.
9. LAGALLY, K. M., R. J. ROBERTSON, K. I. GALLAGHER, R. GEARHART,
and F. L. GOSS. Ratings of perceived exertion during low- and high-intensity
resistance exercise by young adults. Percept. Mot. Skills 94: 723-731, 2002.
10. LAGALLY, K. M., S. T. MCCAW, G. T. YOUNG, H. C. MEDEMA, and D. Q.
THOMAS. Ratings of perceived exertion and muscle activity during the bench
press exercise in recreational and novice lifters. J. Strength Cond. Res. 18: 359364, 2004.
11. LOMBARDI, V. P. Safe maximum testing. In: Beginning Weight Training. A.
Lockhart and J. Mott (Eds.). Dubuque, IA: W. C. Brown, 1989, pp. 197-204.
12
12. MCCAW, S. T. and J. J. FRIDAY. A comparison of muscle activity between a
free weight and machine bench press. J. Strength Cond. Res. 8: 259-264, 1994.
13. PANDOLF, K. B., D. S. BILLINGS, L. L. DROLET, N. A. PIMENTAL, and M.
N. SAWKA. Differentiated ratings of perceived exertion and various
physiological responses during prolonged upper and lower body exercise. Eur. J.
Appl. Physiol. 53: 5-11, 1984.
14. PINCIVERO, D. M., A. J. COELHO, and R. M. CAMPY. Gender differences in
perceived exertion during fatiguing knee extension. Med. Sci. Sports. Exerc. 36:
109-117, 2004.
15. PINCIVERO, D. M., A. J. COELHO, R. M. CAMPY, Y. SALFETNIKOV, and
A. BRIGHT. The effects of voluntary contraction intensity and gender on
perceived exertion during isokinetic quadriceps exercise. Eur. J. Appl. Physiol.
84: 221-226, 2001.
16. PINCIVERO, D. M., P. T. DIXON, and A. J. COELHO. Knee extensor torque,
work, and EMG during subjectively graded dynamic contractions. Muscle Nerve.
28: 54-61, 2003
17. PINCIVERO, D. M., and W. S. GEAR. Quadriceps activation and perceived
exertion during a high intensity, steady state contraction to failure. Muscle Nerve
23: 514-520, 2000.
18. ROBERTSON, R. J., and B. J. NOBLE. Perception of physical exertion: methods,
mediators, and applications. Exerc. Sport Sci. Rev. 25: 407-452, 1997.
19. ROBERTSON, R. J., F. L. GOSS, J. RUTKOWSKI, et al. Concurrent validation
of the OMNI perceived exertion scale for resistance exercise. Med. Sci. Sports
Exerc. 35: 333-341, 2003.
20. SUMINSKI, R. R., R. J. ROBERTSON, S. ARSLANIAN, et al. Perception of
effort during resistance exercise. J. Strength Cond. Res. 11: 261-265, 1997.
13
TABLE 1. Subject Characteristics (N = 20)
Height (cm.)
166.9+6.9
Mass (kg.)
67.7+12.5
Age (yrs.)
21.3+2.2
% fat (3-site skinfold)
27.4+4.7
Chest press 1-RM (kg.)
36.4+8.9
Knee extension (right leg) 1-RM (kg.)
40.5+6.0
13
* Values are means + standard deviations
TABLE 2. RPE Responses to Six Resistance Exercise Intensities (N = 20)
Intensity (% 1-RM)
Exercise
40%
50%
60%
70%
80%
90%
0.9+0.8
2.0+1.3
3.7+1.6
5.3+1.2
6.6+0.9
8.2+0.8
0-3
0-6
1-7
3-7
5-8
6-9
2.0+1.3
3.6+1.2
4.9+1.7
6.1+1.7
7.0+1.5*
7.7+1.9*
Knee
Extension
Mean+SD
Range
Chest Press
Mean+SD
Range
0-6
1-6
2-8
3-8
5-10
4-10
*within an exercise, means with single asterisks (*) are not significantly different at the p < 0.01 level
TABLE 3. EMG Responses to Six Resistance Exercise Intensities. (N = 16)
Intensity (% 1-RM)
Exercise
Muscle Group
40%
50%
60%
70%
80%
90%
Knee
Extension
Vastus
Medialis
0.14+0.06
0.17+0.07
0.17+0.05*
0.21+0.06*
0.23+0.08
0.23+0.10
0.17+0.07
0.21+0.14
0.35+0.50
0.23+0.13
0.21+0.09
0.19+0.15
Chest Press
Pectoralis
Major
Triceps
0.17+0.08
0.21+0.12
0.21+0.09
0.25+0.12
0.26+0.12
Values are means + standard deviations reported as a proportion of the isometric reference position
* within a muscle group, means with asterisks (*) are significantly different (P<0.01)
0.24+0.17
CHAPTER II
EXTENDED LITERATURE REVIEW
Introduction
The purpose of this study was to evaluate ratings of perceived exertion (RPE)
from the OMNI-RES and muscle activity responses during the knee extension and chest
press resistance exercises performed at six relative exercise intensities. This chapter
presents a review of the current literature relevant to the relationships between resistance
exercise intensity and RPE, the influence of physiological mediators on RPE during
resistance exercise, and RPE assessment procedures used during resistance exercise.
Mediators Of Ratings Of Perceived Exertion During Resistance Exercise
Perceived exertion is defined as the subjective effort, strain, discomfort and/or
fatigue experienced during an exercise task (19). RPE is a widely accepted method for
monitoring and prescribing the intensity of aerobic exercise. The rationale for the use of
RPE to prescribe aerobic exercise intensity is based on evidence that shows that RPE is
related to various physiological responses. Borg’s model of the Effort Continua states
that the subjective response to an exercise stimulus involves three main effort continua:
physiological, perceptual, and performance (1, 27). The link between physiological and
perceptual responses during exercise suggests that perceived exertion provides similar
information regarding exercise performance as do physiological variables. Based on this
model, a key element of perceived exertion research is to identify the physiological
responses linked to perceived exertion in order to provide a greater understanding of
perception during exercise and to increase the applicability of perceived exertion scales in
health/fitness settings.
17
Perceived exertion during dynamic aerobic exercise has been shown to be related
to a number of physiological responses. A large body of research has demonstrated links
between RPE and oxygen uptake (VO2), ventilation (VE), blood lactic acid concentration
[Hla], and heart rate (HR) during aerobic exercise (19). These data provide the rationale
for using RPE to prescribe and regulate the intensity of aerobic exercise.
Recently, there has been an increased interest in using RPE to prescribe resistance
exercise intensity. A number of investigations have identified several potential mediators
of RPE during resistance exercise. Research thus far suggests that relative exercise
intensity (%1-RM and %MVC) (9,10,16,17,21,23,24,29), blood lactic acid concentration
[Hla] (13,16,21,29), and muscle activity (EMG) (3,12,16,18,25) may have potential roles
as mediators of RPE during resistance exercise.
Exercise Intensity And Ratings Of Perceived Exertion
There is much support for a relationship between RPE and relative exercise
intensity (%1-RM or %MVC) of resistance exercise. Suminski et al. (29) examined RPE
during 50% and 70% 1-RM. The subjects provided ratings of perceived exertion for the
overall body (RPE-O) after performing three sets of ten repetitions of seven different
exercises at these two intensities. The results showed that RPE-O was higher at 70% 1RM than at 50% 1-RM for all seven exercises.
Pierce et al. (21) evaluated perceived exertion responses prior to and following an
eight-week resistance-training program. The training program involved training twice a
day, three times a week, for eight weeks. The training protocol emphasized large musclemass exercises and a high training volume. Subjects performed Pre- and Post- testing
consisting of a squat 1-RM and seven sets of 10 repetitions of parallel squats at 45%,
18
55% and 62.5% of the initial 1-RM. RPE was collected following each set of the squat
test during the Pre- and Post-testing. RPE was found to be significantly lower following
the training compared to Pre-training, which is not surprising given that the squat 1-RM
increased as a result of training. Thus, the absolute load that was lifted during Posttraining represented a lower relative intensity than during the Pre-training assessment.
These results show that RPE decreased when relative exercise intensity decreased.
Further support for a relationship between RPE and intensity of resistance
exercise was demonstrated using a paradigm in which total work was held constant while
the % 1-RM was varied (9,16,17,18,20). When total work is held constant, the possibility
that RPE responses are dependent on the work performed is eliminated. Lagally et al.
(17) assessed the perception of exertion during the chest press, leg press, latissimus dorsi
pull down, triceps press down, biceps curl, shoulder press and seated calf raise exercises
at 30% and 90% 1-RM. Subjects performed fifteen repetitions at 30% 1-RM and five
repetitions at 90% 1-RM. The results indicated that for all seven exercises there were
uniform increases in RPE in response to increases in intensity with total work held
constant. Lagally et al. also found similar results for the biceps curl performed at 30%,
60%, and 90% 1-RM (16) and for the bench press at 60% and 80% 1-RM (18) when total
work was constant. RPE increased as resistance exercise intensity increased, indicating
that RPE was related to the % 1-RM lifted.
The aforementioned investigations evaluated RPE during exercises including both
eccentric and concentric muscle actions. O’Connor et al. (20) investigated perceived
exertion responses during eccentric-only resistance exercise. Subjects performed
eccentric muscle action (i.e. elbow extension) at 80%, 100%, and 120% MVC. After
19
each elbow extension, an investigator raised the weight and the subject provided a rating
of perceived exertion. The number of repetitions was varied (45, 36, and 30,
respectively) so as to equate the groups on total work performed. Mean perceived
exertion values increased during the eccentric work in association with increased exercise
intensity.
RPE has also been examined during isokinetic and isometric resistance exercise.
When examining the performance of submaximal, isokinetic, concentric quadriceps
contractions at 10 different intensities, Pincivero et al. (23) found that perceived exertion
increased significantly and linearly as a function of contraction intensity. Similarly,
when Pincivero et al. (24) had subjects perform voluntary isometric contraction of the
quadriceps at 10 different intensities, RPE responses increased linearly as exercise
intensity levels increased. The consistently proven relationship between RPE and
contraction intensity indicates the likelihood that intensity does act as a mediator of RPE
during resistance exercise. Therefore, it is concluded that RPE increases with increases
in resistance exercise intensity. Furthermore, it can be concluded that the increase in
RPE resulted from a systematic increase in the percentage of 1-RM lifted and not the
total work performed. This suggests a causal relationship between RPE and %1-RM.
Electromyography And Ratings Of Perceived Exertion During Resistance Exercise
Electromyography (EMG) represents the level and pattern of muscle activation
and therefore its relationship to RPE may provide additional insight into the mechanisms
mediating the perception of effort during resistance exercise (12). Sensory responses to
all forms of exercise are believed to be a function of the neuromuscular system. (2,3,7,26)
It seems likely that both feedforward (motor outflow transmitted to the motor cortex
20
simultaneously transmitted to the sensory cortex) and feedback (afferent information
arising from peripheral proprioception) components contribute to evaluating the
magnitude of a given contraction (3).
A neuromuscular feedforward mechanism may play a role in setting the intensity
of exertional perceptions during dynamic resistance exercise (16). The theory of the
feedforward mechanism is that when the motor cortex sends efferent messages to the
muscles to contract, it also sends corollary signals to the sensory cortex (3), where the
perception of exertion is regulated. Therefore, as muscle activity (EMG) increases, an
increase in the number of corollary commands received by the sensory cortex causes the
exertional sensations to increase. Thus, corresponding increases in EMG and RPE
suggest that these two variables may be functionally related (16).
Several recent investigations have demonstrated corresponding increases between
EMG and RPE. Lagally et al. evaluated RPE and EMG during the dynamic bench press
performed at 60% and 80% 1-RM (18) and the biceps curl performed at 30%, 60%, and
90% 1-RM (16). Both RPE and EMG increased in a corresponding manner as the %1RM increased.
Hasson et al. (12) sought to determine if there was a relationship between the
amplitude and frequency content of the surface EMG and RPE during sustained handgrip
exercise. The right hand was supinated, grasping a modified handgrip dynamometer and
maximal voluntary contraction (MVC) was calculated as the average of three consecutive
trials. Subjects were then asked to produce and maintain a contractile force of 50% MVC
for as long as possible. EMG activity and RPE values were recorded at the onset of the
contraction and at 10-second intervals throughout the contraction. The results
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demonstrated that during sustained isometric exercise, both RPE and RMS (root mean
squared or signal amplitude) increased over time while MPF (mean power frequency)
decreased. Correlations between RPE and MPF and RMS were .89 and .96, respectively.
This indicates that changes in the perception of effort are related to changes in both the
amplitude and frequency content of the EMG signal (12).
Pincivero et al. (25) assessed isometric EMG of the quadriceps and perceived
exertion during a sustained isometric contraction equivalent to 80% MVC held to the
point of failure. The major finding of this study demonstrated that during a highintensity, steady-state muscle contraction (80% maximum voluntary contraction or
MVC), quadriceps EMG and perceived exertion both increased. The corresponding
increases in EMG and RPE noted in the above investigations suggest that a
neurophysiological link functions during resistance exercise to signal exertional
perceptions and indicates that these two variables may be functionally related (16).
Blood Lactic Acid Concentration And Ratings Of Perceived Exertion During
Resistance Exercise
A consistent finding has been that blood lactate concentrations are related to RPE
during resistance exercise (15,16,29). Kraemer et al. (15) conducted a study in which
subjects performed three sets of the bench press, seated latissimus dorsi pull down, leg
extension and leg curl exercises at a 10-RM load that was continued until muscular
failure. Blood samples were taken and RPE values were assessed systematically
throughout the study. The results showed that exercise produced significant increases in
lactate concentrations and RPE. Suminski et al. (29) reported that when subjects
performed resistance exercise at 50% and 70% of a 1-RM, increases in intensity were
22
paralleled by an increase in perceptions of exertion and an increase in [Hla]. Similarly,
Lagally et al. (16) found that [Hla] increased significantly from pre- to post- exercise
during three different intensities (30%, 60% and 90% 1-RM). These increases in [Hla]
corresponded with increases in RPE.
Hollander et al. (13) conducted a study in which subjects performed 4 sets of 12
repetitions for the bench press, leg extension, military press, and leg curl exercises at
80% of the 10-RM. The subjects participated in a concentric-only session and an
eccentric-only session and RPE was recorded after each set for each exercise. A baseline
blood sample was taken and another sample was collected immediately following the
fourth set of the fourth exercise and 15 minutes post-exercise. Both RPE and blood
lactate were higher during the concentric-only muscle contraction session than during the
eccentric-only muscle contraction session. These findings support previous research
suggesting that lactate concentrations are related to RPE and that higher ratings of
perceived exertion are induced, in part, by lactate (13). Whether [Hla] acts as an
independent mediator of RPE remains unclear, but the evidence suggests that [Hla] may
act as a mediator of the intensity of RPE during resistance exercise.
Ratings Of Perceived Exertion For The Active Muscle Versus Ratings Of Perceived
Exertion For The Overall Body
Previous studies examined either RPE-O (29), RPE-AM (9,20), or both (16,18).
Several studies have compared RPE-O with RPE-AM (16,17,18,28). The results from
these studies showed that both RPE-AM and RPE-O increased significantly as resistance
exercise intensity increased, but the active muscle ratings were significantly higher than
the overall body ratings at all intensities. A higher active muscle rating than overall body
23
rating indicates that the regionalized sensations of discomfort and strain felt in the active
muscles were more intense than the generalized sensations for the overall body.
Therefore, active muscle ratings of perceived exertion may provide a better subjective
indicator of the intensity of resistance exercise than overall body ratings of perceived
exertion. The higher active muscle rating of perceived exertion may also suggest that the
physiological factors that mediate perceived exertion during resistance exercise are
primarily peripheral events specific to the active muscles, such as blood or muscle lactic
acid accumulation, neuromotor (EMG) signals, and/or phosphocreatine depletion (17).
Assessment Procedures For RPE During Resistance Exercise
Until recently, perceived exertion during resistance exercise was assessed using
either the Borg 15-Category or CR-10 RPE scales. Ratings from both scales have been
shown to increase in a linear fashion with increases in resistance exercise intensity
(9,16,17,18,23,24). The Borg 15- Category RPE scale is constructed so that certain
psychophysical functions can be assessed according to the basic assumption that
physiological strain grows linearly with exercise intensity and that perception should
follow the same linear increase (19). The numbers on the Borg RPE scale range from 6
to 20, with 6 representing no exertion and 20 representing maximal exertion. This scale
is an interval scale and gives information about the increment of the response from one
category to the next. The benefits of the Borg scale are that it is commonly used for
assessing perceived exertion during aerobic exercise (4,5,6,8,11,14,22) and resistance
exercise (9,10,16,17,20,21) and it allows for a wide range of responses in which the given
ratings grow linearly with exercise intensity (19). However, this range of possible
responses is unclear to some subjects and does not have as clear of a relation with indices
24
of resistance exercise intensity as it does with indices of aerobic exercise intensity, such
as heart rate. For this reason, some researchers have favored the CR-10 scale to measure
perceived exertion during resistance exercise.
The Borg 10-point category-ratio (CR-10) scale was designed to relate to
physiological responses that increase in a non-linear fashion, such as blood [Hla]. This
scale uses both category and ratio properties, with numbers that range from 0 to 10. A
rating of 0 is associated with the verbal descriptor “nothing at all” and a rating of 10 with
“very, very strong”. The verbal descriptors are set to allow free magnitude estimation
between the number 10 and maximal. This means a rating of greater than 10 can be
given, and additionally, decimals can be expressed. The advantages to using this scale
are that there is no ceiling on the rating that can be given and it is useful when studying
variables that increase in a non-linear fashion. However, ratings of perceived exertion
from the CR-10 scale may not demonstrate a simple linear relationship to exercise
intensity.
In response to the confusion over which scale was appropriate to use for
resistance exercise, Robertson et al. (28) developed the OMNI-RES (resistance exercise
scale). This scale has both verbal and mode specific pictorial descriptors distributed
along a comparatively narrow numerical response range, (0-10). In addition the OMNIRES is designed to have broadly generalizable properties, meaning that it is widely
applicable to different types of individuals and to different types of activities. Robertson
et al. (28) examined the concurrent validity of this scale for resistance exercise using total
weight lifted and blood [Hla] as criterion variables. Subjects performed three sets of 4, 8,
and 12 repetitions of the biceps curl and knee extension exercises at 65% 1-RM. RPE
25
for the active muscles and RPE for the overall body were estimated during each exercise
set using the OMNI scale and blood was sampled immediately upon completion of the
biceps curl exercise. A strong positive and linear relationship was observed between
RPE and both total weight and blood [Hla], providing concurrent validity evidence for
use of the OMNI-RES during dynamic resistance exercise (28).
To date, the Robertson et al. (28) investigation is the only to provide information
regarding potential physiological mediators of RPE collected using the OMNI-RES.
Thus, a primary goal of this investigation was to identify additional potential mediators of
perceived exertion from the OMNI-RES during resistance exercise. It was hypothesized
that muscle activity and relative exercise intensity (i.e. %1-RM) could play a role in the
estimation of perceived exertion from the OMNI-RES.
26
References
1. BORG, G. Perceived exertion as an indicator of somatic stress. Scand. J. Rehabil.
Med. 2: 92-98, 1970.
2. BORG, G. A. V., and B. J. NOBLE. Perceived exertion. Exerc. Sport Sci. Rev. 2:
131- 153, 1974.
3. CAFARELLI, E. Peripheral contributions to the perception of effort. Med. Sci.
Sports Exerc. 14: 382-389, 1982.
4. CECI, R., and P. HASSMEN. Self-monitored exercise at three different RPE
intensities in treadmill vs. field running. Med. Sci. Sports Exerc. 23: 732-738,
1991.
5. CHOW, R. J., and J. H. WILMORE. The regulation of exercise intensity by
ratings of perceived exertion. J. Cardiac Rehabil. 4: 382-387, 1984.
6. DUNBAR, C. C., R. J. ROBERTSON, R. BAUN, M. F. BLANDIN, K. METZ,
R. BURDETT, and F. L. GOSS. The validity of regulating exercise intensity by
ratings of perceived exertion. Med. Sci. Sports Exerc. 24: 94-99, 1992.
7. EKBLOM, B., and A. N. GOLDBERG. The influence of training and other
factors on the subjective rate of perceived exertion. Acta Physiol. Scand. 83: 399406, 1971.
8. ESTON, R. G., B. L. DAVIES, and J. G. WILLIAMS. Use of perceived effort
ratings to control exercise intensity in young healthy adults. Eur. J. Appl. Physiol.
56: 222-224, 1987.
9. GEARHART, R. F., F. L. GOSS, K. M. LAGALLY, et al. Ratings of perceived
exertion in active muscle during high-intensity and low-intensity resistance
exercise. J. Strength Cond. Res. 16: 87-91, 2002.
10. GEARHART, R. F., F. L. GOSS, K. M. LAGALLY, J. M. JAKICIC, J.
GALLAGHER, and R. J. ROBERTSON. Standardized scaling procedures for
rating perceived exertion during resistance exercise. J. Strength Cond. Res.
15:320-325, 2001.
27
11. GLASS, S. C., R. G. KNOWLTON, and M. D. BECQUE. Accuracy of RPE from
graded exercise to establish exercise training intensity. Med. Sci. Sports Exerc.
24: 1303-1307, 1992.
12. HASSON, S. M., J. H. WILLIAMS, and J. F. SIGNORILE. Fatigue-induced
changes in myoelectric signal characteristics and perceived exertion. Can. J. Sport
Sci. 14: 99-102, 1989.
13. HOLLANDER, D. B., R. J. DURAND, J. L. TRYNICKI, et al. RPE, pain and
physiological adjustment to concentric and eccentric contractions. Med. Sci.
Sports Exerc. 35: 1017-1025, 2003.
14. KANG, J., J. R. HOFFMAN, H. WALKER, E. C. CHALOUPKA, and A. C.
UTTER. Regulating intensity using perceived exertion during extended exercise
periods. Eur. J. Appl. Physiol. 89: 475-482, 2003.
15. KRAEMER, R. R., E. O. ACEVEDO, D. DZEWALTOWSKI, J. L. KILGORE,
G. R. KRAEMER, and V. D. CASTRACANE. Effects of low-volume resistive
exercise on beta-endorphin and cortisol concentrations. Int. J. Sports Med. 17: 1216, 1996.
16. LAGALLY, K. M., R. J. ROBERTSON, K. I. GALLAGHER, et al. Perceived
exertion, electromyography, and blood lactate during acute bouts of resistance
exercise. Med. Sci. Sports Exerc. 34: 552-559, 2002.
17. LAGALLY, K. M., R. J. ROBERTSON, K. I. GALLAGHER, R. GEARHART,
and F. L. GOSS. Ratings of perceived exertion during low- and high-intensity
resistance exercise by young adults. Percept. Mot. Skills 94: 723-731, 2002.
18. LAGALLY, K. M., S. T. MCCAW, G. T. YOUNG, H. C. MEDEMA, and D. Q.
THOMAS. Ratings of perceived exertion and muscle activity during the bench
press exercise in recreational and novice lifters. J. Strength Cond. Res. 18: 000000, 2004.
19. NOBLE, B. J. and R. J. ROBERTSON. Perceived Exertion. Champaign, IL:
Human Kinetics, 1996, pp. 78-120.
20. O’CONNOR, P. J., M. S. POUDEVIGNE, and J. D. PASLEY. Perceived
exertion responses to novel elbow flexor eccentric action in women and men.
Med. Sci. Sports Exerc. 34: 862-868, 2002.
21. PIERCE, K., R. ROZENEK, and M. H. STONE. Effects of high volume weight
training on lactate, heart rate, and perceived exertion. J. Strength Cond. Res. 7:
211-215, 1993.
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22. PINCIVERO, D. M., A. J. COELHO, and R. M. CAMPY. Gender differences in
perceived exertion during fatiguing knee extension. Med. Sci. Sports. Exerc. 36:
109-117, 2004.
23. PINCIVERO, D. M., A. J. COELHO, R. M. CAMPY, Y. SALFETNIKOV, and
A. BRIGHT. The effects of voluntary contraction intensity and gender on
perceived exertion during isokinetic quadriceps exercise. Eur. J. Appl. Physiol.
84: 221-226, 2001.
24. PINCIVERO, D. M., A. J. COELHO, and W. H. ERIKSON. Perceived exertion
during isometric quadriceps contraction. J. Sports Med. Phys. Fitness 40:319-326,
2000.
25. PINCIVERO, D. M., and W. S. GEAR. Quadriceps activation and perceived
exertion during a high intensity, steady state contraction to failure. Muscle Nerve
23: 514-520, 2000.
26. ROBERTSON, R. J., and B. J. NOBLE. Perception of physical exertion: methods,
mediators, and applications. Exerc. Sport Sci. Rev. 25: 407-452, 1997.
27. ROBERTSON, R. J. Central signals of perceived exertion during dynamic
exercise. Med. Sci. Sports Exerc. 14: 390-396, 1982.
28. ROBERTSON, R. J., F. L. GOSS, J. RUTKOWSKI, et al. Concurrent validation
of the OMNI perceived exertion scale for resistance exercise. Med. Sci. Sports
Exerc. 35: 333-341, 2003.
29. SUMINSKI, R. R., R. J. ROBERTSON, S. ARSLANIAN, et al. Perception of
effort during resistance exercise. J. Strength Cond. Res. 11: 261-265, 1997.
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APPENDIX A
SUBJECT INFORMED CONSENT FORM FOR PARTICIPATION
31
Production of Resistance Exercise Intensity using Ratings of Perceived Exertion
Subject informed consent form for participation
DESCRIPTION:
The purpose of this research investigation is to assess whether or not ratings of
perceived exertion (RPE) can be used to regulate resistance exercise intensity. You will
be asked to rate the difficulty of weight lifting exercise according to a scale called the
Borg Ratings of Perceived Exertion (RPE) Scale. In addition, your muscle activity will
be measured during weight lifting exercise. The experiment will require four separate
visits to Horton Fieldhouse. You are being asked to participate in this research because
you are, (a.) a healthy female (b.) between the ages of 18-35 years (c.) a novice or
recreational lifter and (d.) unfamiliar with the Borg RPE scale.
You will attend a total of four testing sessions on separate days over the course of
a three-week period. The first will be a 60-90 minute orientation session in Horton
Fieldhouse at Illinois State University. Upon arrival at the Biomechanics laboratory, you
will receive an explanation of the procedures to be followed during this study. All
questions will be answered and informed consent will be obtained. At the start of the first
session, you will be asked to complete a Physical Activity Readiness Questionnaire
(PAR-Q) to determine your readiness to participate in exercise and a medical history
questionnaire to help us identify any related medical conditions that may impact the
results of the study. You will be given a description of the tests that you will undergo,
and will be familiarized with the exercise procedures. You will undergo a maximal
weight lifting exercise test. The maximal weight lifting test is a one-repetition maximum
(1-RM) test for the leg extension and chest press exercises. The 1-RM is the maximal
amount of weight you can lift one time. Nautilus leg extension and chest press machines
will be used for testing. For the maximal testing, a test weight will be determined
between 63% and 75% of your body weight. Your one-repetition maximum (1-RM) will
then be estimated from your performance using the test weight, and you will perform one
lift using the 1-RM weight. In addition, the Borg Perceived Exertion scale will be
explained to you, and your height, weight and body composition will be measured during
the first session. Body composition will be assessed using skinfold calipers.
Your second, third and fourth testing sessions will last approximately 60 minutes
each. These three sessions will be separated by at least three days but not more than
seven days. During these sessions, you will be asked to report to the Biomechanics
Laboratory in Horton Fieldhouse at Illinois State University. Your resting blood pressure
will be measured and you will be prepped for placement of the electrodes that will be
used to monitor your muscle activity during weight lifting exercise. Muscle activity will
be monitored using standard surface electrodes and recording procedures. The electrodes
will be secured using tape over your quadriceps (thigh), pectoralis major (upper chest)
and triceps muscles. You will be asked to read the instructions for the Borg RPE scale.
You will then perform weight lifting exercise at six submaximal workloads. You will
33
perform one repetition of the leg extension and chest press exercises at each of the six
workloads. You will be permitted a two to three minute rest between exercise bouts.
You will then be asked to perform four additional lifts for both the leg extension and the
chest press exercise. The workload for each of these lifts will be selected by you based
on your feelings of exertion. You will not be informed of the workloads during the study,
but may review your results upon completion of the study.
RISKS AND BENEFITS:
Current American College of Sports Medicine (ACSM) guidelines recommend that
individuals initially be stratified based on the likelihood of untoward events during
exercise. ACSM guidelines suggest that it is safe for those determined to be at low risk
based on age, health status, symptoms and risk factor information to perform vigorous
exercise without physician supervision. A medical history questionnaire will be
administered to assess your risk, and any individual who is assessed to be at moderate or
high risk for a cardiac event during exercise will be excluded from the investigation.
The risk of weight training exercise is low. Weight training may be harmful in
individuals with high blood pressure and musculoskeletal injuries, or in females who are
pregnant. To minimize these risks, you will complete a medical history questionnaire.
Because you may be required to lift heavy weight and perform an unfamiliar exercise,
you may experience some muscle soreness.
For your participation in this study, you will learn how your body functions during
resistance exercise and how to use the Borg scale to monitor exercise intensity. The
results of this study may provide information on the most effective ways to use the Borg
RPE scale, as well as lead to a better method of prescribing and monitoring exercise
intensity during resistance exercise.
NEW INFORMATION:
You understand that you will be promptly notified if any new information, either
good or bad, about weight training, muscle activity or RPE develops during the course of
this study and which may cause you to change your mind about continuing to participate.
CONFIDENTIALITY:
All records pertaining to your involvement in this study will be stored in a locked
file cabinet. Your identity on these case records will be indicated by a case number. This
information will only be accessible to the investigators and their research study staff.
You understand that you do not have to take part in this study and, should you
change your mind, that you can withdraw from the study at any time. Your decision
whether or not to participate in this study or to withdraw from participation will have no
effect on your academic standing at Illinois State University or your current or future care
at this institution, or any other benefits to which you are entitled. You also understand
34
that you may be removed from the research study by the investigators if you do not
follow the instructions of the investigators. There will be no charge to you for
participation in this study.
ADDITIONAL INFORMATION
I have been told that Illinois State University, like virtually all other Universities
in the United States, does not have a mechanism for compensation of the injured research
subject. Therefore, I understand that I cannot look to any such mechanism to receive
financial remuneration for any such injuries resulting from my participation in this
project. If physical injury occurs as a direct result of such research, emergency treatment,
which is available to the general public, will be available to me. Dr. Lagally cannot
assume financial responsibilities or liability for the expenses of such treatment.
VOLUNTARY CONSENT:
I certify that I have read the preceding, or it has been read to me, and I understand
its contents. Any questions I have pertaining to the research have been, and will continue
to be answered by the investigators listed at the beginning of this consent form at the
phone numbers given. Any questions I have concerning my rights as a research subject at
Illinois State University will be answered by Nancy Latham at 309-438-8451. A copy of
this consent form will be given to me. My signature below means that I have freely
agreed to participate in this project.
_____________________________
Subject’s Signature
__________________
Date
_____________________________
Witness Signature
__________________
Date
INVESTIGATOR’S CERTIFICATION:
I certify that the nature and purpose, the potential benefits, and possible risks
associated with participation in this research study have been explained to the above
individual and that any questions about this information have been answered.
_____________________________
Investigator’s Signature
____________________
Date
Dr. Kristen Lagally, School of KNR, (309) 438-3229
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