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A Unique Method for Predicting Cardiorespiratory
Fitness Using Rating of Perceived Exertion
1) Department of Epidemiology, National Institute for Longevity Sciences (NILS) 2) Institute of Health and Sport Sciences, University of Tsukuba Abstract The purpose of this study was to develop a
(5): 255-261, 2001 http://www.jstage.jst.go.jp/en/ simple and convenient indirect method for estimating Keywords: maximal
rating of perceived exertion (RPE) during a submaximal f o u r he a l th y Ja p a ne s e m e n, a ge d 2 0 t o 6 4 ye a r s , Introduction
volunteered to participate in the study. The subjects wererandomly divided into two groups, a validation (V) group Low levels of cardiorespiratory fitness and physical (n=100) and a cross-validation (CV) group (n=54). The V inactivity have been associated with an increased risk of and CV groups performed a maximal cycling test and the contracting several chronic disease states (Blair et al., 1989; Paffenbarger et al., 1986), including coronary documentation of three categories (overall, chest, legs) of artery disease, stroke, hypertension, diabetes, and some RPE, up to a rating of 15. Prediction equations of VO forms of cancer. Direct measurement of maximal oxygen were developed by multiple regression analysis the V group were 2462 ± 484 ml·min–1 and 1349 ± 334 cardiorespiratory fitness, requires considerable expense ml·min-1, respectively. Correlational analyses indicated in terms of equipment and medical supervision, and that the workrate (W) at which the legs RPE (RPE might cause dyspnea, panting, leg pain and fatigue in a reached 15 or higher was evaluated first (W The anaerobic threshold (AT) determined as the lactate threshold (LT) has been regarded as one of the most (r=0.790), respectively. The developed prediction useful indices in prescribing exercise intensity. Firstly, A T o r LT w hi ch r e flec ts th e eff ic i enc y o f a er o b ic (kgm·min–1) – 15.84age (yr) + 13.06 metabolism in peripheral skeletal muscles could be an weight (kg) + 1365 (R=0.849, SEE=261 ml·min–1) VO index of cardiorespiratory fitness (Ivy et al., 1980).
Secondly, these same indices can be used as possible 665 (R=0.816, SEE=195 ml·min–1) Results of a cross- indices of effective and safe training intensity (Jacobs et v ali dation analysi s indi ca ted a simi lar es ti mati on al., 1986). In general, however, it is difficult to use AT in (r=0.793 and 0.853, and SEE=240 ml·min–1 and 183 most public health-oriented facilities because of the ml·min–1) compared with the above equations developed complexity and high cost of the technique. A number of from data of the V group. Reliability coefficients of V methods for estimating AT have been developed (Brettoni et al., 1989; Conconi et al., 1982), but these are not useful significant and there was no difference in the mean value from the perspective of accuracy and simplicity (Francis between trials 1 and 2. The “RPE method” developed for estimating cardiorespiratory fitness is not only a unique A number of indirect methods for predicting VO2max indirect method but also a valid and useful tool in various using heart rate (HR) during submaximal exercise settings of exercise prescription. J Physiol Anthropol 20 (Åstrand and Ryhming, 1954; Margaria et al., 1965; Siconolfi et al., 1982; Miyashita et al., 1985) have been Table 1 Physical and physiological characteristics of the subjects
developed. However, HR can be affected by many factors, e.g., environmental temperature and humidity, state of health and mind, and especially medications (caffeine and β-blockers (Noble and Robertson, 1997)). Also, the validity of these methods has been questioned by some investigators (Gutmann et al., 1981; Pollock et al., 1986).
Therefore, the development of alternate methods for estimating LT without HR are needed.
Borg’s 15-grade rating of perceived exertion scale (RPE) (Borg, 1973) corresponding to AT during a graded exercise test has been reported by many investigators to range from 12 to 14 (Robertson and Noble, 1997) and it is not influenced by exercise modality, gender, age, training habits and medications (Noble and Robertson, 1997). Ithas been shown that RPE is closely correlated with relative exercise intensity measured by VO (Robertson, 1982). On the basis of the above findings, it seems possible to assess cardiorespiratory fitness from the RPE. Nevertheless, such RPE methods for predicting during a maximal GCT using a Monark cycle ergometer (type 818E). The cycle ergometer was calibrated weekly using a 4.0-kg reference weight. The effect of the height p r e d i c t e d f r o m a m e a s u r e o f w o r k r a t e a n d R P E of the seat on oxygen consumption and lower limb respectively during submaximal graded exercise. The kinematics has been established; thus, height of the seat purpose of this study was to develop a simple, convenient, was standardized by having the subject sit on the cycle ergometer and extend a leg onto the pedal in the down (ml·min–1) from indices of workrate and RPE position. Final height of the seat was adjusted so that leg respectively. In the present study, the “RPE method” is extension was approximately 165–170 degree angle at the defined as a method which enables prediction of VO knee joint. Following a resting electrocardiogram (ECG) using the data collected during a submaximal and a blood pressure recording, the exercise test began with a 2 minute of unloaded warm-up cycling task (0 kg) at 60 rpm. Following the warm-up, a workrate (W) of 90 Subjects and Methods
kgm·min–1 was given and the W was increased by 90kgm·min–1 each minute until volitional exhaustion occurred. Pulmonary ventilation (VE) and gas exchange One hundred and fifty-four healthy Japanese men, aged were measured breath-by-breath with an on-line data 20 to 64 years (mean 40.8 ± 12.2 yr), volunteered to acquisition system (Mijnhardt Oxycon αSystem). The participate in this study. The subjects were randomly turbine volume transducer was calibrated daily with a 3- divided into two groups; a validation group (N=100) and a liter calibration syringe. A continuous sample of expired cross-validation group (N=54) (see Table 1 for subject ga s w as tr a n s p or te d v i a h ea te d s am p l i n g l i n e s to description). The physical activity level of the subjects electronic gas analyzers for measurement of oxygen and was either sedentary (N=106) or moderately active c a r b o n d i o x i d e c o n c en t r a t i o n i n e x p i r e d a i r a n d (N=48). The moderately active subjects engaged in subsequent estimation of oxygen uptake (VO ), carbon walking, jogging, swimming, and/or some other form of dioxide output (VCO ) and the respiratory exchange ratio exercise for approximately 30 to 60 minutes, 1–5 days a (R). The gas analyzers were calibrated before each test week (mean=3.5 days). None of them were elite athletes with certified gases of known concentration (17.0%O and or highly trained cyclists. The sedentary subjects 5.0%CO ). Throughout each test, ECG and HR were reported no recent participation in regular physical m o n i t o r e d c o n t i n u o u s l y ( D i n a s c o p e 5 0 1 , F u k u d a activity. None of the subjects received any medication known to affect the variables measured. Prior to the initiation of the study, all subjects were informed of the of VO (an increase of less than 150 ml·min–1) despite an risks and benefits associated with the investigation and increase in workrate; 2) the highest R value during the signed a statement of informed consent.
final stage of the GCT was required to be > 1.10; 3)attainment of an age-predicted maximal HR was madeonly if the subjects met at least two of the above three criteria. For detection of LT, a venous blood sample (1 mleach) was drawn each minute from the antecubital veinof each subject during the exercise test. Determination ofthe blood lactate concentration was performed by anelectrochemical enzymatic method using a lactateanalyzer (model 1500L, Yellow Springs Ins titute).
Lactate threshold was conceptually defined as the pointat which the rate of lactate production and diffusionexceeded the rate of its removal, i.e., blood lactateconcentration increased non-linearly. To identify this point, the log [blood lactate concentration] - log [VO ] transformation method was used (Beaver et al., 1985).
Evaluating 3 categories of RPE during GCTsubmax Seven days after the maximal cycling test, GCTsubmax was performed with documentation of RPE and HR only(see Fig. 1) terminated at RPE of 15. Three separatecategories of RPE were recorded: 1) An RPE general feelings of physical fatigue; 2) An RPE feelings associated with the cardiopulmonary system, and3) An R PE , des cri bing feelings of str ai n in the Fig. 1 Protocol of submaximal graded cycling test and recording
exercising muscles and joints (Pandolf et al., 1984).
These three RPEs were recorded one at a time during thelast 15 seconds of each stage by having each subject pointto an appropriate number to describe each feeling on the RPE scale, held within easy reach by an investigator.
Subjects were asked to give the RPE in the following Physical and physiological characteristics of the subjects are shown in Table 1. There were essentially no significant difference (P>0.05) between the validation group and the cross-validation group in all variables.
Pearson product-moment correlation coefficients (r) were 2462 ± 484 and 1349 ± 334 ml·min–1, respectively and in the cross-validation group 2462 ± 407 and 1377 ± example, indicated as the workrate at which an RPE F i g u r e 2 s h o w s m e a n ( ± S D ) o f w o r k r a t e s of 15 or higher was first evaluated. Prediction equations corresponding to each RPE. Workrates estimated by were developed from the data of the validation group by using a multiple linear regression analysis procedure . Two dotted lines show the mean of W at AT (558 (stepwise method). The dependent variables were the V kgm·min–1) and maximal exercise (1128 kgm·min–1).
Workrates at RPE of 13 were approximately equivalent to the maximal GCT. The independent variables were 1) age AT level. Ex er cis e intensi ty (p ercent of ma xim al 2) weight 3) height and 4) W variables, most significantly workrate) at each RPE of 15 were 73.9 % for RPE standard error of estimate (SEE = SD (1 – r2)1/2 ) and I n Ta b le 2 t he co r r ela t i o n co e ffi c i en ts be tw ee n percent SEE (%SEE = (SEE/mean) ·100) were calculated to established the accuracy of the equations. The cross- validity of the equations developed in the present study was assessed in the cross-validation group by correlation coefficients, SEE and %SEE. Test-retest reliability of the respectively. Required time for estimation of WRPE legs 15 was 10.3 ± 2.1 min including warming up time (2 min) correlation coefficients and paired t-test using randomly drawn subjects (n=37) with a period of two days between Multiple regression analyses by stepwise method using trials 1 and 2. The probability of making a Type I error was set at P ≤ 0.05 in paired t-test or P ≤ 0.001 in weight and height as potential independent variables yielded the equations in Table 3. In the equation of Fig. 2 Means and standard deviations of workrates corresponding to each RPE.
height was not selected as an independent Table 2 Correlation coefficients of workrate values at each RPEs
variable because height had no significant correlation weight was not selected in the equation of VO Relationships of the predicted values with measured values in the cross-validation group are presented in Fig.
3. Correlation coefficients were significant (r=0.793 and 0.853), and SEE and %SEE in the predicted VO against the measured values were 240 ml·min–1 and 183 ml·min–1, 9.7 % and 13.3 %, respectively.
The results of test-retest reliability are illustrated in Fig.
4 . C o m p a r i s o n b e t w e e n t r i a l 1 a n d 2 r e l i a b i l i t y coefficients were significant (r=0.891 for VO Discussion
There are a number of methods of predicting the / HR response to submaximal exercise on a cycle ergometer. The treadmill ergometer, or stepping bench or box are perhaps the most widely used methods(Shephard et al., 1968). Prediction is based on thesupposition that there is essentially a linear relationship cardiac stimulants such as atropine accelerate exercise Medications such as beta-blocking agents and cardiac HR (Davies and Sargeant, 1979). Therefore, HR methods stimulants are routinely used by patients with essential hypertension who have a similar lifestyle to clinically dosage of these medications is periodically titrated to normal people. As an example, beta-blocking agents such achieve an optimal therapeutic benefit. In such cases, it as propranolol and atenolol attenuate exercise HR (Hossack et al., 1980; Squires et al., 1982), whereas the RPE. The correlation between RPE and %VO Table 3 Prediction equations of VO
(R = 0.849, SEE = 261 ml·min–1, % SEE = 10.6%) (R = 0.816, SEE = 195 ml·min–1, % SEE = 14.5%) Fig. 3 Relationship of the predicted VO
measured values in the cross-validation group.
Fig. 4 Relationship of VO
not change even if the dosage of these medications isperiodically titrated (Robertson, 1982). Hence, the RPE allowed some trial and error in evaluating the 3 categories of RPE in the beginning stage of a test.
in clinically normal people but also in patients with Thus, the subjects could communicate accurate RPEs to essential hypertension. Furthermore, the RPE method is the examiners, especially, in the latter half of GCTsubmax.
frequently used as an adjunct to standard physiological and clinical responses during a graded exercise test.
significantly to the high precision (good SEE and %SEE) Measurement of perceived exertion during exercise testing is an easily applied procedure, requiring no bioelectri cal instrumentation or extensive s caling most intense perceptual signal must be noted during expertise on the part of a subject, patient, athlete, or cycle ergometry. Robertson et al. (1979) reported that, in physical education student (Noble and Robertson, 1997).
men, the perceptual signal from the legs was typically For these reasons the use of an indirect method for most intense (i.e., dominant) than from either the chest evaluating cardiorespiratory fitness such as the RPE or the overall signal. It also appeared that RPE linked to blood lactate concentration through its relation Fi tchett (1985) repor ted that the a sses sment of to exercise intensity during an incremented test protocol cardiorespiratory fitness by a incremental exercise test (Robertson et al., 1986). On the basis of these reports it protocol is more accurate than a method using a steady has been hypo thesized in thi s s tud y tha t, u si ng 3 study could be terminated within 8 to 12 minutes in men most intense signal would be able to be identified.
with average cardiorespiratory fitness. The duration of The evidences supporting the above hypothesis are shown in Fig. 2 and Table 2. As illustrated in Fig. 2, VO during submaximal cycling at 100, 150 and 200 workrates estimated by the perceptual signal from legs tended to be smaller than by the chest and overall signals.
previously reported to range from 2.0% to 5.6%, of which 90% is attributed to biological variability and 10% to technological error (Katch et al., 1982). It may be . In Table 2, especially noteworthy is the fact difficult for indirect test methods to achieve %SEE of 10% t h a t W v a l u e s b a s e d o n R P E or lower. According to previous reports (Åstrand and R y h m i n g , 1 9 5 4 ; R o w el l e t a l. , 1 9 6 4 ) , c o r r el a t i o n coefficients between measured and predicted values f i n d i n g s m a y b e d u e t o t he ex e r c i s e m o d e ( c yc le using HR have been reported to range from r=0.58 to ergometry). The workrate at which the RPE r=0.95, and %SEE have ranged from 7% to 27% (Åstrand and Ryhming, 1954; Fox, 1973; Margaria et al., 1965; Rowell et al., 1964). Greiwe et al. (1995) reported that (r=0.790), respectively. It was expected that the higher %SEE of ACSM’s convenient submaximal cycle ergometer the RPE score, the greater was the correlation between the an RPE of 15 was the highest score recorded during the in the current study may be better than other indirect , W corresponding to this RPE had the highest Test-retest reliability of the developed equations was was observed for a W value corresponding to an RPE examined using 37 randomly drawn subjects predicting of 14. This may be due to the fact that AT occurs in most from the main cohort of subjects (Fig. 4). In a comparison cases at an RPE between 12 and 14 (Robertson and Noble, between trials 1 and 2, reliability coefficients for VO2max 1997). These results in the validation group supported the were r=0.891 and 0.870, respectively. The above findings of Robertson’s report (1979).
values were significant and the difference between trials In the current study the prediction equation of VO was not significant. Therefore, it is suggested that VO (Table 3). These two equations indicated that despite thesignificant correlation between age and cardiorespiratory Conclusion
with them. The reason that weight was not selected as an A simple and convenient method for predicting VO2max was developed in this study. The workrate (W) the case of forced adoption for weight as an independent variable, multiple r (R=0.819) and SEE (195 ml·min–1) as the best independent variables yielded the including warming up time (2 min), which was equivalent HRmax” test by Miyashita et al. (1985), the – 15.84age (yr) + 13.06weight (kg) + 1365 most famous method in Japan. The purpose of that test was to estimate the workrate corresponding to 75% of maximal HR to each person. According to their report, various physical and clinical risks were not found during HRmax test”. In the current study, mean of exercise intensity (percent of maximal workrate) for Acknowledgement This study was supported in part by
Human Beings in the Ecosystem, Tsukuba Advanced Research Alliance (TARA), University of Tsukuba.
v a l i d a t i o n g r o u p s w e r e c r o s s - v a l i d a t e d ( F i g . 3 ) .
Correlation coefficients between the RPE score and V References
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