Based on HR and Perceived Exertion, in Sportivnaya kardiologiya i fiziologiya krovoobrashcheniya (Sports. Cardiology and Physiology of Circulation), Moscow:.
ISSN 0362-1197, Human Physiology, 2008, Vol. 34, No. 6, pp. 766–770. © Pleiades Publishing, Inc., 2008. Original Russian Text © E.B. Akimov, V.M. Alekseev, 2008, published in Fiziologiya Cheloveka, 2008, Vol. 34, No. 6, pp. 126–130.
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Effects of the Production of Perceived Exertion during Cycle Ergometry E. B. Akimov and V. M. Alekseev Russian State University of Physical Education, Sports, and Tourism, Moscow, Russia Received May 21, 2008
Abstract—Physiological and biomechanical effects of aerobic exercise varying in intensity were studied on the basis of the subjects' perceived exertion. It was demonstrated that exercise regulated with the use of a 50–100 rating scale was characterized by reliably stable heart-rate and respiratory reactions and biomechanical responses. The relative working heart rate (HR) expressed in percent of the individual HRmax was found to be closely correlated with the values on the 50–100 scale within a wide range during exercise with constant or increasing perceived exertion. DOI: 10.1134/S0362119708060169
Sufficiently intense and long exercise causes a feeling of exertion. Borg proposed the first scale for measuring this characteristic for practical purposes in 1966 [1]. In subsequent years, Borg and other researchers intensely studied both the phenomenology and the physiological and psychophysical mechanisms of subjective rating of perceived exertion (RPE) and developed other scales and methods [1–5]. The RPE has been shown to be directly related to the exercise intensity, relative aerobic intensity (measured by oxygen consumption expressed in percent of the maximal oxygen consumption, %MOC), and heart rate (HR) in subjects of different ages, sexes, and degrees of training during global and regional physical exercises of various types. The RPE is an informative index of the degree of exertion in persons working at various air temperatures and other atmospheric conditions. It has been demonstrated that the RPE is a good predictor of the maximal oxygen consumption [6] and work capacity in submaximal tests (similar to PWC170) [1, 4]. The subjective RPE is used in training for orbital spaceflights [7, 8] and has been recommended for a wider range of training and rehabilitation activities. Subjective criteria may be used for estimating the adequacy of training tasks to the physical capacity of an athlete’s body, the more so as exercise intensity in many sports, especially cyclic ones, has reached its limit or is approaching it. Examination of male and female elite ski racers during training has shown a significant positive relationship between the RPE measured immediately after training and the mean HR [9]. In many cases, however, individual pulse and subjective estimates deviate from the RPE–HR regression curve. The practical implications of the existing subjective perceptual criteria and methods are likely to pertain to the overall assessment of a training session rather than to its programming.
The use of subjective sensations, referred to as selfregulation, is recommended as an auxiliary means for correcting the initially set level of exertion (measured by, e.g., the HR) and/or the main way of regulating exercise intensity [2]. This requires preliminary evaluation (calibration) of the RPE–HR relationship [3] because the subjective estimates determined using Borg’s 6–20 scale [10] may vary in different athletes at the same HR because of individual differences in the maximum HR. We studied physiological (HR, lung ventilation (LV), and its components) and biomechanical (pedaling power, pedaling rate (PR), and ergometer flywheel resistance) responses during aerobic cycle ergometer exercises of different intensities performed on different days on the basis of the subjects' sensations alone. Production of perceived exertion (PPE) is performance of physical exercise with an intensity that causes specific sensations of the degree of exertion corresponding to target points of a scale or to verbal or other designations. Subjects themselves regulate the set degrees of exertion via empirical selection (setting) and control (changing) of mechanical variables, namely, the force applied to the support and/or the movement rate. For the PPE and subjective RPE, we used Alekseev’s 50–100 scale [5], based on the numerical continuum of the relative working HR (%HRmax) and a uniform distribution of verbally designated RPEs: 100, 95 (very high, VH), 90, 85 (high, H), 80, 75 (moderate, M), 70, 65 (low, L), 60, 55 (very low, VL), and 50. Twenty-seven volunteers (students of a physical education institution), including 17 men and 10 women with a mean age of 23 ±1.6 years, body weight of 70 ± 12 kg, and height of 171 ± 7 cm performed exercise on a Monark 828E cycle ergometer. On the first day, the exercise intensity was increased at a step of 40 W (3 min at every step) until failure, i.e., inability to con-
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tinue exercise at a PR of about 60 rpm. The subjects estimated their perceived exertion at the end of every minute. Production was performed on the following days. The subjects were not informed about the mode of PPE until the beginning of this part of the study. Group 1 (five men and five women) performed exercises at an exertion score of 75 for 10 min three times on different days. Groups 2 (five men and four women) and 3 (six men and two women) produced perceived exertion with a degree changing every 5 min; the exercise mode of group 2 was 75–85–75 points, and that of group 3 was 55–95–75 points. These exercises were performed for 15 min three times. To warm up, the subjects pedaled without a load for 5 min. No more than one test a day was performed. The breaks between the tests were from two to seven days. The subjects did not know the values of the recorded parameters. Seeing neither the readings on the ergometer display nor the position of its pendulum, the subjects themselves adjusted the flywheel resistance, which they could change when they felt appropriate by means of an adjustment handle. The subjects were also not instructed as to the choice and regulation of the PR. Mechanical parameters (the resistance and PR) were recorded every 30 s. The HR was recorded continuously with the use of a Polar S610i monitor and was expressed in absolute (bpm) or relative (%HRmax) units. The highest HR recorded during one of the 15-s intervals of continuous recording of the HR in the test with a stepwise increase in the exercise intensity “until failure” was taken to be the HRmax. The LV and respiration rate (RR) were continuously measured using an SV3000 portable volumeter (Russia) transmitting the data to a computer in the online mode. The results were treated by standard mathematical statistical methods with the GraphPad InStat software. Production of the same perceived exertion on different days caused similar physiological and biomechanical effects. The mean PPE set for all tests performed on three different days was 76.1 ((75 + 78.3 + 75)/3). As can be seen in the table, the HR, LV, RR, power, and resistance were almost the same on different days. Tendencies towards a somewhat lower HR and higher power may have been related to the effect of training adaptations. The differences in tidal volume (TV) and PR (on average, 9 and 6%, respectively) were significant, which, however, did not lead to significant differences in their derivatives (LV and power). Thus, in tests on production of the same perceived exertion on different days, both physiological (HR, LV, and RR) and mechanical (power, which is the main energy criterion of physical exercise, and the resistance determining the effort of the legs) responses were reproduced sufficiently accurately. This was true for both men and women. The results allow us to conclude that PPE using the 50–100 scale is a reliable method for planning aerobic exercise. Our data agree with those reported by other authors who used Borg’s 6–20 scale HUMAN PHYSIOLOGY
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Mean physiological and biomechanical parameters (n = 81) of the same perceived exertion (score 76.1) produced on different days Parameter HR, bpm LV, l/min RR, cycles/min TV, l/cycle Power, W Resistance, kg PR, rpm
Day 1
Day 2
Day 3
144.5 43.6 31.1 1.40 124.6 2.04 60.9
143.3 45.0 29.4 1.53*** 126.5 1.97 64.4^^
140.4 44.2 30.8 1.44** 127.4 2.03 62.9^
Note: See the text for abbreviations. *** Significant difference between tests 1 and 2 (p < 0.001); ** significant difference between tests 2 and 3 (p < 0.01); ^^ significant difference between tests 1 and 2 (p < 0.01); ^ significant difference between tests 2 and 3 (p < 0.05).
[10] in studies on the reproduction and self-regulation of running [11], cycle ergometer exercises for legs [12] and legs or hands [13], and rowing [14]. PPE with score 75 (moderate). The HR, LV, RR, and TV continuously increased, reflecting both the warming up and “drift” of the oxygen-transport function. The mechanical parameters of the work remained stable. The power, resistance, and PR stabilized as early as the end of the first minute and remained almost unchanged afterwards. Both the absolute values of and the changes in the same parameters were similar on all three days of testing. PPE in the 75–85–75 (moderate–high–moderate) mode. In tests with varying PPE, the subjects more often regulated the exercise power via changing the flywheel resistance (the effort) than via changing the PR. The mean mechanical parameters were the following: power, 100 W (the first 5 min), 165 W (the next 5 min), and 119 W (the last 5 min); resistance, 1.7, 2.7, and 1.9 kg; and PR, 59, 61, and 63 rpm, respectively. At a score of 75, the power during the last 5 min was 19% higher (p < 0.05) than during the first 5 min, mainly due to a change in the resistance (11%) rather than the PR (7%), whose differences were nonsignificant. The mean HRs at scores of 75 and 85 were, respectively, 71 and 87% of the HRmax (129 and 157 bpm). During the last 5 min of the exercise, the HR was 154 bpm (85% of the HRmax) because of the “pulse debt” left after the preceding high exertion. This was considerably higher than the set PPE (score 75). This may explain the discrepancy between the pulse-based and subjective estimates of exertion recorded after a decrease in the power. The LV, RR, and TV during the last 5 min of the test were also higher because of the effect of the “ventilation debt” after the preceding high (score 85) exertion. Different physiological parameters (HR, LV, RR, and TV) changed similarly during the 75–85-75 PPE.
768 W 300 270 240 210 180 150 120 90 60 30 0 kg 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 1:00
AKIMOV, ALEKSEEV bpm 200
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Fig. 1. The (a) power, (b) resistance, (c) HR, and (d) LV in eight subjects (group 3) performing PPE in the 55–95–75 mode on different days. Circles, squares, and triangles show the data for tests 1, 2, and 3, respectively. The vertical bars show the SD (test 2).
PPE in the 55–95–75 (very low–very high–moderate) mode. As in the preceding case, the power was initially set and regulated in the course of PPE mainly via changing the effort (i.e., resistance). The mechanical parameters were the following: power, 55, 193, and 114 W; resistance, 0.8, 2.9, and 1.7 kg; and PR, 69, 67, and 67 rpm, respectively. During the last 5 min (moderate exertion), both the resistance and the power were intermediate (114 W and 1.7 kg, respectively) (Fig. 1). These values only slightly and nonsignificantly (p > 0.05) differed from the theoretical values calculated as the means between those for scores of 55 and 95 (123 W and 1.85 kg, respectively). The PPE at a score of 95 was accompanied by a continuous decrease in the power from the initially set level (through changing the resistance) and increase in the HR and LV. This may have been accounted for by high degrees of both aerobic and anaerobic/glycolytic exertion at the very high exertion level. Upon the change in PPE from a score of 95 to a score of 75, the decrease in HR and LV lagged and did not reach the level corresponding to the power and effort. Thus, the changes in the physiological and mechanical parameters during the 55–95–75 PPE in general and at the stage of a score of 95 in particular were specific, the changes being differently directed and transitional processes occurring at different rates.
The effects of PPE in men (n = 11) and women (n = 6) were similar with respect to the pattern of changes in the parameters studied in the course of exercise with varying RPE. Relationship between the relative HR and power and perceptual criteria of exertion. As should be expected, the HR and RPE were closely and positively related to each other during exercise with stepwise increasing intensity, which agrees with numerous literature data. This was also characteristic of PPE in general. At the same time, individual PPE values could either correspond or not correspond to the %HRmax values. As can be seen in Fig. 2a, the HR considerably deviated from the regression line in some cases (on average, by 10–12% of the HRmax, or about 20 bpm). The “pulse debt” after the preceding more intense exercise (groups 2 and 3 during the last 5 min) was one of the factors accounting for this finding. The HR for a PPE score of 95 (group 3) was considerably lower (85% of the HRmax). The reason for this phenomenon is not obvious. This phenomenon can hardly be explained by characteristics of the autonomic control of heart functioning because we did not observe marked deviations of HR at the other two levels of exertion (scores 55 and 75). Nor can the low HR be related to an impaired capacity for producing the “expected” power because of deterioration of the functional capacity of HUMAN PHYSIOLOGY
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Power, % of the maximum (b) 100
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Fig. 2. PPE (solid symbols) and RPE (open symbols) in groups 1 (triangles, n = 10), 2 (circles, n = 9), and 3 (squares, n = 8). (a) Relationship between HR and subjective perceptual criteria of exertion (y = 0.98x + 2.9, r = 0.96): PPE (the dot-and-dash line; y = 0.75x + 19.4, r = 0.92) and RPE (the dotted line, y = 1.03x – 0.3, r = 0.99). (b) Relationship between the power expressed in percent of the power at the last step of the stepwise test and subjective perceptual criteria of exertion (y = 1.72x – 71, r = 0.98): PPE (the dot-and-dash line; y = 1.64x – 69, r = 0.97) and RPE (the dotted line, y = 1.77x – 73.1, r = 0.99).
the body or the psychoemotional state of the subjects: the relative mechanical power at the PPE level of 95 was very close to the regression line (Fig. 2b). The closeness of the values of relative mechanical power recorded during PPE to the regression line showed that humans can accurately determine and regulate the intensity of exercise on the basis of subjective sensations. Our data show that the diagnostic implications of subjective criteria for both estimation of exertion and PPE are comparable to those of HR, which is widely used for assessment of physical exertion.
in percent of the individual maximum HR (HRmax) is closely related to the values of the 50–100 scale in a wide range. After a decrease in the PPE level (and, hence, the power), the decrease in %HRmax lags because of the physiologically explainable inertness of the pulse response (as well as other autonomic responses). (4) PPE using the 50–100 scale may be used as a separate, independent method for programming and/or regulating exertion during predominantly aerobic exercises.
CONCLUSIONS
REFERENCES
(1) PPE by men and women during a cycle ergometer test with the use of a 50–100 rating scale is reliable and stable: pulse and ventilatory responses and biomechanical responses reproduced on different days were very close to one another. (2) Self-regulated PPE is characterized by sufficiently accurate setting and regulation of the parameters of mechanical work performed under conditions of both increasing and decreasing power. The amount of physical effort is the decisive factor in changing the power during PPE. (3) In the course of production of constant or increasing exertion, the relative working HR expressed
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