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The Effect of Training Intensity on Ratings of Perceived Exertion E. Mi Haskvitz, R. L. Seip ', J. Y Weitman, A. D. Rogol, A. Weitman Exercise Physiology Laboratory (EMH, RLS, AW), Curry School of Education and Department of Pediatrics (JYW, ADR), Pharmacology (ADR), Internal Medicine (AW), Health Sciences Center; The Biodynamics Institute (ADR), University of Virginia, Charlottesville, VA 22903
Abstract E. Mi Haskvitz, R. L. Seip, J. V. Weitman, A. D. Rogol and A. Weitman, The Effect of Training Intensity on Ratings of Perceived Exertion. Tnt J Sports Med, Vol 13, No5,pp377—383, 1992.
ences were observed for \T02 or velocity at LT, FBLC and peak. Both training groups increased V02 at LT, FBLC and peak as a result of training (p < 0.05), with the > LT group exhibiting greater improvement than the @LT group (V02 at LT, FBLC of 2.0, 2.5 and 4.0 mM and peak increased by 6.4, 5.3, 5.1, 4.0 and 4.7 ml/kgmin 1for @LT andby 10.4,
We examined the effects of intensity of train-
ing on ratings of perceived exertion (RPE) at the lactate threshold (LT), fixed blood lactate concentrations (FBLC) of 2.0, 2.5 and 4.0 mM and peak in 25 untrained eumenor-
rheic women (±SD: age
30.9±4.1 yrs; height
65.5±7.6 kg) who completed 165.7±5.9 cm; weight one year of run training. Subjects were recruited as sedentary controls or were randomly assigned to one of two training groups: 1) at the lactate threshold (@LT) or 2) above the lactate threshold (> LT). The @LT group trained at veloc-
ity LT and the > LT group trained at the velocity midway between velocity LT and peak velocity. Training subjects were reevaluated every fourth menstrual cycle and training intensity was adjusted. The control group was reassessed at menstrual cycle 12. Before training no among group differ-
Introduction
Similar findings were observed for the velocity associated with these lactate concentrations. No pre/post differences were observed in V02 or velocity for the control group. In spite of the differential training response, RPE remained stable at LT and FBLC of 2.0, 2.5 and 4.0 mM and peak (5i RPE= 12.3, 14.7, 15.8, 17.6 and 19.3, respectively). We conclude that RPE remains stable at LT, FBLC and peak independent of changes in fitness or training intensity. There-
fore, if blood lactate concentrations are used for exercise prescription, RPE may provide a suitable means for regulating training intensity. Key words
RPE, lactate threshold, fixed blood lactate concentrations, exercise, running
dated (6, 14), the lactate threshold (LT) and fixed blood lactate
concentrations (FBLC) may be important determinants for Ratings of perceived exertion (RPE) have been used in both clinical and experimental settings to monitor exercise intensity (6, 15). RPE has also been suggested to be a
useful tool for exercise prescription (1, 3, 7, 8, 18, 22). Although mechanisms by which individuals perceive the intensity of exertion during exercise have not yet been fully eluci-
*Present address: Dr. R. L. Seip
Department of Preventive Medicine Lipid Research Center Washington University School of Medicine Campus Box 8046 4566 Scott Avenue St. Louis, MO 63110 Jnt.J.SportsMed. 13(1992)377—383 GeorgThieme Verlag StuttgartNew York
RPE(5, 7, 10, 14,20). The LT and FBLC are also thought to be important training intensities for exercise prescription (9, 13, 17, 21, 23, 26, 28—30) and research shows that training more markedly affects LT and FBLC compared to V02 max (9, 17, 24,25, 30).
Recently it has been shown that RPE at LT and/or FBLC is not affected by gender (7, 18), training state (7, 12, 20), exercise modality (10) or specificity of training (5). These cross sectional data suggest that RPE can be used in a longitudinal fashion to monitor exercise intensity. However, for RPE to be an effective tool for exercise prescription, it is im-
portant to understand the effects of training intensity on RPE at LT and FBLC. Thus, the purpose of the present study was to determine the effect of training intensity on RPE at the LT and FBLC during a one year endurance training program. We hypothesized that different training intensities (i. e., high versus low intensity) would not affect RPE at LT, FBLC or peak.
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9.2, 8.6, 5.1 and 5.9 /kgmin' for > LT; p LT, n = 9). For the @LT and > LT groups physiological parameters and RPE were assessed during the early follicular
phase of the menstrual cycle at baseline (days 1—3) and every fourth menstrual cycle thereafter for the next 12 menstrual cycles (approximately one year). The control group was assessed
at baseline and after 12 menstrual cycles. Measurement of RPE, the lactate threshold, fixed blood lactate concentrations, velocity at LT, and peak oxygen consumption were made at each assessment.
micro-Scholander technique) before and after each test. Heart rates were determined electrocardiographically.
Lactate Threshold and Fixed Blood Lactate Concentrations An indwelling venous catheter was placed in the back of the hand and blood samples were taken at rest and at the end of each work stage. Subjects continued to run during sampling, with one hand resting on the treadmill rail. To prevent clotting, a heparinized saline solution was infused after each blood sample was obtained and the line was cleared prior to each sampling. Whole blood samples were analyzed immediately with an automated lactate analyzer (Yellow Springs Instrument Model 23L).
The lactate threshold was determined by examining the blood lactate-velocity relationship observed during the V02 peak test. The highest velocity attained that was not associated with an elevation in blood lactate concen-
tration above baseline was designated as the velocity associated with lactate threshold (V-LT). This occurred just prior to the curvilinear increase in blood lactate observed with subsequent exercise intensities. A lactate elevation of at least 0.2
mM (the error associated with the lactate analyzer) was required for LT determination. The VO2 corresponding to V-LT (from individual plots of V02 vs velocity) was designated as
the V02 associated with the lactate threshold (VO2 LT). Velocities associated with fixed blood lactate concentrations of 2.0, 2.5 and 4.0 mM were determined from the curvilinear rise in blood lactate observed from the velocity-blood lactate relationship. V02 values associated with fixed blood lactate concentrations were determined in a manner identical to that described for velocity-LT (27).
V02 Peak \T02 peak as determined using a continuous, horizontal running treadmill protocol. The initial treadmill velocity was 60 rn/mm, with an increase of 10 rn/mm in each
Ratings of Perceived Exertion Prior to the treadmill test standardized directions for RPE were read to each subject (16). The wording
subsequent 3 mm stage. Subjects were given verbal encourage-
directed the subject to focus on the sensations of muscle and joint strain in the exercising legs as well as cardiopulmonary sensations. The subjects were instructed to give an overall rating of perceived exertion, which was to represent an integra-
ment throughout the test. The test was terminated when the subject would not complete a given worldoad. V02 peak was chosen as the highest oxygen uptake achieved over any one minute period during the test (27).
tion of all exercise sensations. The ratings were obtained during the last 30 seconds of each work stage.
Metabolic Measures Metabolic data were collected using standard open circuit spirometric techniques. Inspired ventilation was measured using a previously calibrated dry gas meter (Rayfield RAM 9200) fitted with a potentiometer. Output from the potentiometer was continuously integrated into an Apple lIe computer (Rayfield REP200). Expired ventilation was channeled from a Hans Rudolph high-velocity valve through lowiesistance plastic tubing into a 7-liter mixing chamber. The concentrations of oxygen and carbon dioxide in the mixing chamber were continuously sampled by an Applied Electrochemistry S-3A oxygen analyzer and a Beckman LB-2 carbon dioxide analyzer, respectively. Output from the gas analyzers
was continuously integrated into the Apple lie computer (Rayfield REP200). The gas analyzers were calibrated using commercial gases of known concentrations (analyzed by the
Training Protocol Both training groups completed similar weekly mileage at different training intensities. Training began at five miles per week and progressed to 24 miles per week by week 20. Subjects continued to run 24 miles per week through week 39. At week 40 the weekly mileage increased by 1.25 miles per week for three out of four weeks. Subjects trained five to six days per week, with three supervised sessions weekly.
Intensity of training was dependent on group assignment. The @LT group trained at the velocity corresponding to V-LT. The > LT group trained at the velocity midway between V-LT and peak velocity three times per week (on supervised days). Up to one half of their weekly mileage, not to exceed five miles per session (15 miles per week), was covered
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Methods
mt. J. Sports Med. 13(1992) 379
The Effect of Training Intensity on Ratings ofPerceivedExertion
Table 1 Changes in V02 (ml/kgmin1) and RPE at LT, FBLC of 2.0,2.5 and 4.0 mM and peak as a result of one year of run training.
Variable
V02 LT 2.0 mM 2.5 mM 4.0 mM Peak
(n=9) Post
Pre (SD)
> LT Group
@LT Group
Control Group (n =7)
(SD)
Pre
(SD)
(n=9*) Post (SD)
Pre (SD)
(SD)
Post
24.2 (6.4) 31.2 (6.1) 33.4 (6.8) 37.0 (7.9) 39.7 (8.1)
24.5 (6.5) 30.0 (6.1) 31.9 (6.7) 35.8 (7.4) 37.8 (8.0)
23.3 (4.3) 30.7 (5.1) 32.8 (5.4) 38.0 (5.6) 41.7 (6.2)
29.7 (6.9) 36.0 (5.9) 37.9 (5.8) 42.0 (5.8) 44.3 (6.1)
26.2 (6.7) 32.7 (6.3) 34.7 (6.4) 39.1 (6.4) 43.5 (5.4)
36.6 (3.4) 41.8 (4.1) 43.3 (4.2) 46.9 (2.1) 47.6 (3.9)
11.3 (1.6) 14.4 (1.6) 15.4 (1.7) 16.7 (1.6) 19.0 (0.8)
11.3 (2.0) 13.9 (2.5) 15.9 (1.6) 17.6 (1.5) 18.3 (2.0)
12.6 (2.6) 14.2 (1.6) 15.2 (2.0) 17.3 (1.5) 19.2 (0.8)
12.4 (2.1) 15.6 (2.3) 16.8 (2.3) 18.4 (1.8) 19.8 (0.4)
11.8 (2.2) 13.7 (1.8) 14.8 (2.2) 16.3 (2.9) 19.2 (0.7)
12.9 (2.1) 15.2 (3.1) 16.2 (3.1) 17.3 (2.8) 18.9 (1.6)
LI 2.0 mM 2.5 mM 4.0 mM Peak
*
n=8forVO2
*
for (102 the following was found: 1) Both @LT and > LI increased V02 at LI, FBLC of 2.0, 2.5 and 4.0mM and peak after training (p LI group than in the group. 3) No changes were observed in the control group.
**
for RPE the following was found: 1) There were no significant between group differences. 2) There was a significant main effect for pre/post observation at 2.5 and 4.0 mM, but no significant difference with post hoc testing.
at this pace. The remainder of their weekly mileage and training sessions were completed at the pace corresponding to VLT. All subjects were allowed to walk or run in a training zone which corresponded to 10 m/min from their assigned pace. During the supervised sessions the training pace was monitored and subjects were given feedback so that corrections could be made. Training logs were maintained during the non-supervised days. Training pace was adjusted following each physiological assessment.
Statistical Analysis A 2 x 3 ANOVA with repeated measures was used to compare baseline and menstrual cycle 12 data for the three groups. For the two training groups changes over time were analyzed using a two-way analysis of variance with repeated measures with one within and one between group variable. An alpha level of p < 0.05 was chosen a priori. When mean differences were observed, post hoc comparisons were made using the General Linear Models Procedure using the Least Squares Means (SAS 5.18, Cary, N. C., 1985). Results
The effects of the present training regimen on the reproductive axis have been presented in detail elsewhere (19). Briefly, no within or between group changes were observed for menstrual cycle length over the course of one year. Therefore, the time frame for testing was similar among the three groups.
The physiological responses to the present training program have also been discussed in detail elsewhere
(25). However, in order to relate the RPE findings to the physiological changes observed with training, the physiological responses are presented below. Table 1 presents the oxygen consumption and RPE values for LT, FBLC of 2.0 mM, 2.5 mM, 4.0 mM and peak before and after one year of training in the
control, @LT and > LT groups. For V02 in the > LT group one subject's data was eliminated due to an error in V02 assess-
ment. However, because the RPE data were accurate, nine subjects were included in the analysis of this variable. Before training no among group differences were observed for V02 at
LT, FBLC and peak. Both training groups significantly increased V02 at LT, FBLC and peak as a result of training (p LT group exhibiting a significantly greater improvement than the @LT group. For the @LT group V02 at LT, FBLC of 2.0, 2.5 and 4.0mM and peak increased by 6.4, 5.3, 5.1, 4.0 and 4.7 l/kgminandforthe > LTgroup
the increases were 10.4, 9.2, 8.6, 5.1 and 5.9 ml/kgmin' (p < 0.05). No significant pre/post differences were observed in the control group for V02 at LT, FBLC and peak.
Similar findings were observed for velocity at LT, FBLC and peak. No between group differences were observed before training for velocity at LT. Both groups significantly increased velocity at LT, FBLC and peak as a result of training (p LT group. Velocity at LT, FBLC of 2.0, 2.5, 4.0mM and peak increased by 26.7, 31.0, 31.3, 29.9 and 23.4 rn/mm for the
@LT group and 48.7, 47.9, 46.8, 46.2 and 30.3 rn/mm increases were observed for the > LT group.
Table 1 also presents the RPE values for LT, FBLC and peak before and after one year of training. There was a significant main effect for pre/post observations at 2.5
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RPE* * *
E. M. Haskvitz, R. L. Seip, J. Y. Weitman, A. D. Rogol, A. Weitman
mt. J. Sports Med. 13 (1992) 40 C
E
a)
C
35
0) E
30
E
20 cycle 12
cycle 8 cycle 4 cycles of training
50
30
0 >
25 baseline
cycle 4 cycle 8 cycles of training
cycle 12
baseline
cycle 4
cycle 12
55
E
45
a)
E
E
40 E
50 45
E
p 0
35
0 >
c'J
C
E 0)
35
c'J
baseline
C
40
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0>
45
E
30 baseline
cycle 4 cycle 8 cycles of training
40 35
cycle 12
cycle 8 cycles of training
60 C
E
55
0) E cc
0 0> ci)
50 45
baseline
cycle 4 cycle 8 cycles of training
cycle 12
Fig. 1 Time course (every fourth menstrual cycle) of adaptation in
improved similarly from baseline to cycle 4. From cycle 4 to cycle 12
oxygen consumption values at LI, FBLC of 2.0, 2.5 and 4.0 mM and peak in the @LT and > LT groups. Results indicate that both groups
only the > LI group continued to demonstrate improvement. Vertical bars represent SEM.
and 4.0 mM, with no significant differences with post hoc test-
Fig. 3 presents the time course of adaptation in RPE values at LT, FBLC of 2.0, 2.5 and 4.0mM and peak in the @LT and > LT groups. No significant differences were observed for LT, FBLC or peak at any time frame between or within groups with one exception. There was a significant overall between group difference for RPE 2.0, but no significant differences with post hoc testing.
ing. Group mean RPE for LT was 12.3, with a range of group means from 11.3—12.9. At 2.0mM the group mean RPE was 14.7 (13.9—15.6), at 2.5mM the group mean was 15.8 (15.1— 16.8), and at 4.0mM the group mean was 17.6(16.6—18.4). At peak a group mean RPE of 19.3 was observed (range of group means from 18.3 to 19.8).
Fig. I presents the time course of oxygen consumption adaptation at LT, FBLC of 2.0, 2.5 and 4.0 mM and peak at baseline and for menstrual cycles 4, 8 and 12 within the @LT and > LT groups. Within the @LT group the majority of
change was observed from baseline to cycle 4, with little change thereafter. Within the > LT group V02 parameters continued to increase over time. These results are presented in greater detail elsewhere (25).
Fig. 2 presents the time course of adaptation in velocity values at LT, FBLC of 2.0, 2.5 and 4.0mM and peak for the @LT and > LT groups. As was observed for STO2, the rate of change in velocity at LT, FBLC and peak was greater in the > LT group compared to the @LT group (P < 0.05).
Discussion
The major finding of the present study was that
in spite of the differential response to training for V02 and velocity, ratings of perceived exertion remained stable at the lactate threshold, FBLC of 2.0, 2.5 and 4.0mM and peak.
As expected, the high intensity (> LT) training group showed improvement in V02 at LT, FBLC and peak throughout the training period. The low intensity (@LT) group, however, increased V02 at LT, FBLC and peak during the first four menstrual cycles and essentially showed no further improvements during the rest of the training period. The velocity data are consistent with the V02 findings. Both groups increased velocity at LT, FBLC and peak during the
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380
mt. J. Sports Med. 13(1992) 381
The Effect of Training Intensity on Ratings ofPerceivedExertion 220
180
E
160
200
E
180
140
E
0
.Q120 100
0 C.)
a)
> baseline
cycle 4 cycle 8 cycles of training
140 120
cycie 12
. 220 200
220
180
200
160
180
cycle 4
cycle 8 cycles of training
cycle 12
baseline
cycle 8 cycle 4 cycles of training
cycle 12
160
-
> baseline
140
cycle 12
cycle 8 cycle 4 cycles of training
260 240 220
200 a)
180
> 160 baseline
cycle 8 cycle 4 cycles of training
cycle 12
velocity at LT, FBLC of 2.0, 2.5 and 4.0 mM and peak in the @LT and
from baseline to cycle 4. From cycle 4 to cycle 12 only the > LI group continued to demonstrate improvement. Vertical bars represent
> LI groups. Results indicate that both groups improved similarly
SEM.
first four menstrual cycles of training. Although the > LT training group continued to increase velocity with training, the @LT group did not continue to show improvement. The V02 and velocity findings clearly show the differential training response between the two training intensities. These findings have been discussed in greater detail elsewhere (25).
values at LT, FBLC and peak remained stable (Table 1, Fig. 3).
Fig. 2 Time course (every fourth menstrual cycle) of adaptation in
Previous research has indicated that RPE at LT, FBLC and peak are unaffected by fitness level (7, 12, 20), gender (7, 18), exercise modality (10) and specificity of training (5). Because of the stable relationship observed between LT, FBLC and RPE, blood lactate may be a good summary indicator of perceptual cues for RPE (5, 7, 10, 14, 20). Although blood lactate levels are probably not perceived directly, blood
lactate rises in association with other exercise phenomena such as muscle strain and increased ventilation, which can be perceived or subconsciously monitored. The present data extend these findings to intensity of training and support the data of Hill et al. (11), who reported that high intensity training did not alter the RPE value at the ventilatory threshold. In the present study a differential training response was observed with higher intensity training (Table 1, Figs. 1 and 2), but the RPE
Although most physiological variables change linearly with work load, perceived exertion, when ratio-scaling methods are utilized, increases with a positively accelerating function (4). Because blood lactate is one of the few physiological variables that follows the same type of function, this also lends indirect support to the reported relationship between blood lactate and perceived exertion (4).
The present findings may have applicability for exercise prescription. For improvement in V02 and veloc-
ity at LT, FBCL and peak, it has been suggested that LT and/or FBLC are critical training intensities (9, 13, 17, 21, 23, 26, 28—30). Regardless of which intensity is utilized, the fact that the ratings of perceived exertion remained stable at the LT and FBLC throughout the year of training, despite increasing fitness, suggests that if blood lactate concentrations are used in exercise prescription, RPE may provide a suitable means for
regulating training intensity. As fitness levels improve, a higher training intensity (i. e. running velocity or % VO2max) is required to exercise at the prescribed RPE allowing for con-
tinued improvement with training without the need for re-
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140
120
baseline
240
E E
160
c\j
0
382 mt. J. Sports Med. 13 (1992)
E. M. Haskvitz, R. L. Seip, J. Y. Weitman, A. D. Rogol, A. Weitman
20
20
18
18
16
16
c a
9
14 12
w 10 U-
It
8
6 baseline
cycle 4
cycle 8
baseline
cycle 12
cycle 4
cycles of training
20
20
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18
16
cycle 12
E
16
o 14
14 IS
ui 12
12
U-
uJ U-
It 10
It
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cycles of training
baseline
cycle 8
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8 baseline
cycle 4
cycles of training
cycle 8
cycle 12
cycles of training
18
a 16 0. 14
Ui
U-
It
12 10
--c-- a'LT —'— >LT
8 baseline
cycle 4 cycle 8 cycles of training
Fig. 3 Time course (every fourth menstrual cycle) of adaptation in RPE at LI, FBLC of 2.0, 2.5 and 4.0 mM and peak in the OLT and > LT
peated laboratory assessment. However, it should be realized
that not all subjects provide reliable estimates of RPE. For these subjects use of RPE for exercise prescription may not be
appropriate. For example, one subject in the > LT group in the present study had an RPE peak ranging from 15—19 over the course of training. While this had no statistical significance, she may not be a good candidate for exercise prescription using RPE. Mean RPE at LT in the present study was 12.3.
This value is slightly higher than the 11.0 value obtained by Seip et al. (20) in male subjects using a similar level treadmill protocol and is slightly lower than the RPE LT of 13.4 reported
by Demello et al. (7) in male and female subjects during a graded treadmill protocol. The RPE LT in the present study is also slightly lower than the 13.6 RPE at anaerobic threshold re-
ported by Purvis et al. (18) for males and females assessed using a cycle ergometer. These differences in RPE at LT may be attributable to variation in the testing protocols as well as the method of determining the LT point. When comparing RPE values at FBLC of 2.0, 2.5 and 4.0 mM, the present data compare favorably. The present RPE values for FBLC of 2.0, 2.5 and 4.0 mM were 14.7, 15.8 and 17.6, respectively, compared to values of 14.5, 15.0 and 16.0 reported by Borg et al. (2)
cycle 12
groups. Results indicate that RPE remained stable in both groups throughout the course of training. Vertical bars represent SEM.
and values of 117, 14.5 and 16.5 reported by Seip et a!. (20).
The agreement observed among studies for RPE values at FBLC provides further evidence for the strong link between RPE and fixed blood lactate concentration during continuous running or cycling.
In summary, training at and above the lactate threshold resulted in a differential training response in previ-
ously sedentary women, with the higher intensity training group improving fitness to a greater extent than the lower intensity group. Despite the different gains in fitness, the RPE at LT and FBLC did not differ over time. The present data support the suggestion that blood lactate may be representative of the physiological cues of effort as measured by RPE. Therefore, we conclude that RPE may be a suitable training regulator when exercise is prescribed based on the lactate threshold and/or fixed blood lactate concentrations. Acknowledgements
This study was supported in part by NIH Grant R01HD20465. The authors gratefully acknowledge Dr. Donald Ball for his contribution to this manuscript in the area of data analysis.
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mt. J. Sports Med. 13(1992) 383
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Esther Haskvitz,
Ph. D., P. T
Department of Physical Therapy
Springfield College 263 Alden Street Springfield, Massachusetts 01109
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References