Download Use of the Rating of Perceived Exertion to Control

Pediatric Exercise Science, 1991, 3, 21 -27
Use of the Rating of Perceived Exertion
to Control Exercise Intensity in Children
John G. Williams, Roger G. Eston, and Clare Stretch
This study examined the ability of 40 children (20 boys and 20 girls), ages
11 to 14 years, to regulate the intensity of their effort using perceived effort
ratings during cycling. The Borg Rating of Perceived Exertion 6 to 20 Scale
was learned and used as a perceptual frame of reference. Maximal oxygen
uptake and power output were predicted from telemetered heart rate data
collected during a submaximal graded exercise test. Subjects were then fully
familiarized with the RPE scale and attended three consecutive sessions of
cycling during which they adjusted the workloads themselves so as to produce effort intensities for scale ratings of 9 (very light), 13 (somewhat hard),
and 17 (very hard). Heart rates were sampled during the final half minute
of each session and the data were submitted to a mixed factorial analysis of
variance. This showed highly sigmficant differences QK.001) between the
three RPE levels but no significant effects for age, gender, or trials. It was
concluded that the RPE is readily learned by older children and adolescents
and is a potentially useful frame of reference when self-regulating effort
intensity during vigorous exercise.
For both children and adults, personal fitness goals are achieved by
involvement in regular, vigorous physical activity. Beneficial adaptations are
induced through an optimal combination of frequency and duration of a particular
type of activity at an appropriate intensity. It is widely agreed that the intensity
dimension of exercise is most difficult to determine. Misperception of intensity
is common and may be a prime reason for lack of adherence to regular exercise.
The problem of misperception of the intensity required during a bout of
vigorous exercise is particularly noticeable in children. Most elementary school
physical education teachers will attest to difficulty in communicating an optimal
intensity and, having decided on a particular level, discover that children are
quite inept at regulating their efforts. Usually they work too hard, too soon.
Evidence for this phenomenon has recently been reported by Bar-Or (2). The
John Williams is with the Dept. of Movement Science, Faculty of Medicine, University of Liverpool, PO Box 147, Liverpool, England L69 3BX. Roger Eston is with the
P.E. Unit, Chinese University of Hong Kong, Shatin, N.T., Hong Kong. Clare Stretch
is with the Advisory Service, Wirral Educ. Authority, Birkenhead, England.
22
- Williams, Eston, and Stretch
use of an organizing schema to aid self-regulation of intensity during sustained,
vigorous activity would be valuable for teachers and pupils alike.
Accurate determination of exercise intensity has been traditionally thought
to require assessment in a suitably equipped exercise physiology laboratory.
However, the Borg 6-20 Rating of Perceived Exertion Scale (WE) (4) which
is shown below, has the potential to render continual laboratory measurement
unnecessary. The scale has been used mainly in two ways: Either a subject
undergoing a graded exercise test is asked to express his or her perception of the
strain inherent in the activity by providing a numerical value that coincides with
a set of verbal expressions of effort (5,15), or it can be used as frame of reference
for producing a particular level of effort (7, 10, 12, 13, 14, 15).
6 No exertion at all
Extremely light
14
15 Hard (heavy)
16
17 Very hard
18
19 Extremely hard
20 Maximal exertion
9 Very light
10
11 Light
12
13 Somewhat hard
Research (7, 10) has shown that young adults are able to produce power
outputs proportional to their measured maximum quite accurately when using
the Borg 6-20 Rating of Perceived Exertion Scale as a frame of reference. We
were interested in whether younger subjects were able to learn the scale and use
it to judge the intensity of their efforts while exercising vigorously.
There has been some research into the effort sense of younger subjects
using the report method mentioned above. Bar-Or (1) found an age effect for a
given workload in cycle ergometry. The ratings of children in the age range
10-12 years were substantially lower than those of adult subjects. Although
ratings were more like those of adults with each 2-year age increment, there was
still a marked disparity in response between the younger (below age 16) and
older subjects (over 18 yrs). Eston and Williams (9) found a close relationship
between RPE, heart rate, and relative exercise intensity in 15- to 17-year-old
boys for cycle ergometry. The results of this study were much the same as those
reported with adult subjects (7).
Our results with older children, using a report mode of eliciting the RPE,
made us wonder whether younger subjects who were at an age when organized,
vigorous exercise was becoming part of their school physical education program
could learn to use scale to gauge exercise intensity. Thus the purpose of the study
was to introduce the concept of an effort rating scale and to assess the ability of
schoolchildren to use the RPE as a frame of reference for regulating the intensity
of their effort while exercising on a cycle ergometer.
Method
The subjects were 20 boys and 20 girls, ages 11 to 14 years, drawn from the 1stand 3rd-year intakes of a secondary school in Cheshire, England (see Table 1
for detailed physical data and predicted maximal oxygen uptake statistics). They
Exercise Intensity in Children
- 23
Table 1
Descriptive Statisticsfor Physical Characteristics
and Predicted Maximal Oxygen Uptake
Subject groups
(yearlsex)
11 Boys
11 Girls
31 Boys
31Girls
Age
(yrs)
M
SD
11.5
11.7
13.8
13.9
0.2
0.4
0.4
0.3
Height
(cm)
M
SO
149.1
149.4
160.8
160.0
4.6
6.0
8.4
9.5
Mass
(kg)
M
SD
35.9
40.0
48.8
46.6
2.6
6.1
8.4
10.5
Predicted
Predicted
V02max
power output
(ml-kg-min-I) (watts)
M
SD
M
SD
47.3
38.1
47.6
39.6
5.6
5.7
6.4
4.9
114.3
104.4
161.2
121.6
15.2
27.8
22.9
26.6
Subjects attended individually on an appointment basis. Testing was carried
out in a large changing room, which was a familiar setting to the children within
the school site. The study was undertaken in two parts and involved four sessions
of testing. On the first visit, physical characteristics were recorded and a submaximal graded exercise test was administered. The purpose of this was to acquire
a physiological data base for the children that would enable the prediction of
maximal oxygen uptake and maximal power output for each subject. More rigorous physiological test procedures were not possible in this school based setting.
The exercise test was given by first determining and recording the saddle
height on the cycle ergometer (Cardiokinetics, electronically braked), then fitting
each subject with a Sport ester^^ PE-3000 for sampling and storing heart rate
each 15 seconds throughout the test. Following this the subject cycled for 4
minutes at a power output of 50 watts (60 rpm). Steady state was assumed if the
difference in heart rate at 3rd and 4th minute was < f 5 bpm (11).
A second bout of cycling at a higher power output was administered at a
level determined from heart rate at the end of the first bout. This was judged by
use of a decision tree modified from Golding et al. (11) so as to be applicable to
both boys and girls. This is shown in Figure 1.
Maximal oxygen consumption (liters-min-') was predicted by plotting
heart rate in the final minute of the first and second workloads on a graph of
heart rate (y-axis) against power output (x-axis), then extending the plot to a
theoretical maximal heart rate (220 minus age), dropping a perpendicular to the
power output axis, and reading off the value at the intersection (11). The preferred method would have been to have measured this variable by open circuit
spirometry. This was not practicable in this instance and is unlikely to be a viable
approach when replicating tests of large groups of children in a typical school
environment. However, an advantage of the techniques used in this study is that
replication of the protocol is possible in most school settings. Descriptive statistics for predicted maximal oxygen consumption are shown in Table 2.
The second phase of this study was implemented between 15 and 21 days
after the predicted maximal oxygen uptake test. Just prior to the start, subjects
24
- Williams, Eston, and Stretch
1st Workload
2nd Workload
1SOW
125W
3rd Workload
75W
I
125W
lOOW
Figure 1 - Modification of the Y's guide to setting cycle ergometry workloads (boys
and girls, ages 11-13 years).
were familiarized with the Borg 6-20 RPE scale and given a copy to keep. It
was made certain that all of the participants in the study fully understood the
verbal expressions and how they were to be interpreted in numerical form. Following explanation of the RPE scale, each child undertook three incremental
exercise levels on each of three days. These were designed to test the ability of
subjects to use the RPE scale in order to produce what they perceived to be effort
intensities that correspond to 9 (very light), 13 (somewhat hard), and 17 (very
hard) and evoke a degree of physical strain associated with each RPE level which
would be reflected in the heart rate record. The required intensity levels were
selected to elicit power outputs of approximately 30,60, and 90%of the individual maximum.
Prior to each trial, the ergometer was individually adjusted and the heart
rate monitor was attached as previously described. Following a short warm-up,
each subject was briefed that helshe was to cycle at 60 rpm for 4 minutes at each
of the prescribed points on the scale displayed directly in front of them. They
were shown how to alter the resistance of the machine and were told that adjustments could be made during the first 3 minutes of the exercise bout. Also, they
were requested and reminded throughout to consult the scale while exercising
and to ensure that their total feeling of exertion was assessed when adjusting the
power outputs. Feedback from all instrument displays was eliminated. Pedaling
rate was maintained with the aid of a metronome. A continuous record of heart
rate was taken. Each exercise bout ended with a short cool-down period.
Results
A--
-
Heart rate data collected in the manner described were submitted to a mixed
factorial analysis of variance for which there were two levels of age, both levels
of gender, three levels of effort to be produced, and three consecutive practice
trials. Descriptive statistics for each of the groupings, levels of RPE, heart rate,
and mean percent predicted heart rate maximum are shown in Table 2. The
analysis confirmed that the-expeeted main effect for level of RPE (heart rate at
Exercise Intensity in Children
- 25
Table 2
Descriptive Statistics for Heart Rates by RPE Level
and Trial Plus Mean O h Predicted Heart Rate Maximum
Group
1. Boys
RPE
level
Heart rate
Trial
M
SD
Mean 010 predicted
max HR
9
13
17
1. Girls
9
13
17
3. Boys
9
13
17
3. Girls
9
13
17
9, 13, and 17, respectively) was highly significant; F(2,72)= 1126.70, p<0.001.
Also significantly different was the main effect of gender (heart rate of girls
being higher than that of boys); F(1,39) =5.28,p<0.05. None of the other main
effects or associated interactions were statistically significant.
26
-
Williams, Eston, and Stretch
Discussion
.-. -
The children in this study had developed a concept of effort. They were able to
comprehend the RPE scale and use it to guide the regulation of the intensity
with which they cycled. This was clearly demonstrated by the highly significant
differences in heart rate response to the request to adjust power outputs corresponding to perceived intensities of 9, 13, and 17 on the Borg Scale using only
the information that was generated from within their own musculoskeletal system
as they exercised. Judging from their heart rate response, they were able to
do this consistently on consecutive occasions. Furthermore, their regulation of
intensity in this manner was independent of both age and gender.
Heart rate levels appear to be high relative to the intended relationship of
the numerical scale. The RPE was originally developed from studies of men
wherein levels of 9, 13, and 17 would convert to approximate heart rates of 90,
130, and 170 beats per minute, respectively. Both developmental and gender
effects for heart rate are reported in the literature. There is decline with age (6),
and levels are higher in girls than in boys (3, 8). On the whole, the results here
are consistent with thesekstablished maturational and gender differences.
The values recorded were perhaps slightly higher than might have been
anticipated in children of this age, particularly at RPE 9. This could be explained
by a likely carryover effect of warm-up and/or an arousal effect brought about
by being in a situation that children probably perceive as undergoing "tests."
Although the subjects in this study readily assimilated the idea of the RPE
scale, it is clear that a children's version would be more meaningful. A 1-10
scale anchored with appropriate expressions of effort translated by placing 1 and
0 on either side of each level from 1 (no exertion, heart rate 110) through 3
(light, heart rate 130), 5 (somewhat hard, heart rate 150), 7 (hard, heart rate
170), to 10 (maximum, heart rate 200) would seem closer to reality for young
adolescents.
A slight lowering of mean heart rate for each level of RPE was witnessed
across trials in the older age band for both boys and girls. Although nonsignificant
in this study, Eston et al. (10) reported a similar, significant trend in a comparable
study of young adults. Close observation of the subjects during procedures and
discussions with these and older subjects who have been involved with the production of effort intensity protocol indicates that they "listen" intently to their
body and try hard to achieve a required intensity. It seems that the process of
effort perception is predominantly direct but can be fined-tuned.
Practice results in increased sensitivitv to the efforts involved and. as with
perception in other modalities, judgments of intensity can be highly accurate. In
this regard the subjects in this study worked alone and regulated effort in accordance with the RPE scale by reference to their own bodily sensations. Most
exercise is taken in the company of others, and the misperception of effort intensity referred to earlier as common in children may well result from a modeling
effect centered upon the more able members of a group. In such situations a
self-regulatory system, however accurate, may be overridden. This aspect is to
be addressed in future research.
In conclusion it is suggested that the RPE scale, or some appropriate young
people's version, is a potentially useful device in the regulation of intensity during vigorous aerobic exercise. Children and those who are unfamiliar with vigorous exercise seem -torequire" some external scaling or grading system early in
their experience to assist the process of effort regulation. This is subsequently
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