European Bulletin Adapted Physical Activity

BRIEF COMMUNICATION

Rating of perceived exertion, physiological parameters and extraversion in patients treated with beta-blockers

Klára Mocková, Jirí Radvanský

Affiliations:

Klára Mocková (biography)
Charles University
2nd Medical faculty - Dept. of Sports Medicine
V Úvalu 84
150 06 Prague 5
Czech Republic
Tel.: +420224435510
Fax.: +420222718637
e-mail: klara.mockova@lfmotol.cuni.cz

Jirí Radvanský
Charles University
2nd Medical faculty - Dept. of Sports Medicine
V Úvalu 84
150 06 Prague 5
Czech Republic

Rating of perceived exertion, physiological parameters and extraversion in patients treated with beta-blockers

Introduction

In terms of adapted physical activities we promote a variety of therapeutic, preventive and recreational exercises. For optimal exercise prescription, frequency, duration and intensity determination is crucial. In terms of intensity, this must be clearly determined in order to produce the desired improvements, but also to ensure that the individual is not overstrained and harmed (Mc Ardle et al. 1996).

Heart rate (HR) is the most frequently used indicator of exercise intensity. However, in the clinical practice of exercise prescription some problems may exist with the accurate use of HR caused by arrhytmias and impaired exercise HR acceleration due to ischaemic heart disease, specifically in an elderly population. The use of HR is rather dubious especially in the home and in during recreational activities. Also, its use in patients being treated with beta-blockers (i.e. patients with abnormal HR exercise reaction) is rather complicated, since the resulting heart rate is a function of at least those variables: an exercise type/intensity and drug level. Even if it could be shown that cardiac patients on beta-blockade had similar improvements after the training programme compared to non-blockade, and HR still seems to be a reliable parameter (Vanhees et al. 1982), the problem remains of changing HR according to time and dosage of the medication. Hence, Borg's Rating of Perceived Exertion (RPE) was suggested (Eston and Connolly 1996) for use in exercise testing and therapy. In addition to its noninvasiveness, low cost and simplicity, it has many advantages for field exercise, and it helps to dose the exercise intensity according to a patient's actual state of health. RPEs are frequently used as part of standard response measurements during graded exercise testing (GXT). Such assessment should provide a good starting point for exercise therapy, where RPEs may be used to control the exercise intensity. One of the aims of this study was therefore to explore whether RPE is a good indicator of physical strain during GXT in cardiovascular patients on beta-blockade in the relationship to "objective" physiological parameters.

According to basic understanding of the perceived exertion as stated by Borg (1998) and Noble and Robertson (1996), the sense of effort is seen as a kind of "Gestalt" and a complex psycho-physiological process that brings together a number of exertional symptoms. It was suggested earlier that RPE is influenced by psychological factors (Morgan 1973; 1994) including temperament characteristics as part of human personality descriptors. Since it was shown that personality traits are related to habitual participation in physical exercise, for example, (Szabo 1992), it might be of interest to explore the relationship between those factors and perceived exertion in populations where exercise and physical activity is considered to be a cornerstone of lifestyle as a primary or secondary means of prevention of so-called physiological disorders. Extraversion, as one of the personality dimensions, refers to such traits described as active, assertive, carefree, dominant, lively, venturesome and sociable (Wise 1995). Extroverts probably need greater sensory stimulation in order to experience a certain level of perception in comparison with introverts. The influence of extraversion on perceived exertion was previously reported in a pilot study by Morgan (1973, 1994). His results opened up the concept of personality factors, showing both the relationship and links to preferred exertion. Our question was whether similar relationships persist in a population of elderly people with cardiovascular disorders.

Materials and Methods

Eighteen female and thirteen male patients treated with selective beta-blockers (or a combination of drugs involving a beta-blocking agent) as a result of ischaemic heart disease and/or hypertension participated in this study (age = 61.1 8.58, BMI = 28.44 4.31). None of the subjects suffered from any disorder which is known to have a possible significant influence on perceived exertion. Inclusion criteria were: under 80 years of age, stabilized on any beta-blocking therapy, belonging to the Weber A-B classification and sedentary (patients reported they had not participated in any form of aerobic conditioning within the last year). Patients were instructed to refrain from any additional exercise, alcohol, smoking and heavy stress for 24 hours before the exercise test.

Firstly, patients completed questionnaires concerning medical history and the Eysenck Personality Inventory (EPI). The EPI consists of 57 closed (yes/no) questions. Its reliability in retesting, as reported by previous studies, was 0.85 and its validity was confirmed by comparison with the Maudsley Personality Inventory (Miglierini and Vonkomer 1979). The subjects then read the RPE scale with standardized instructions (Borg 1998), which were both translated into Czech. Each patient performed one graded exercise test (GXT) protocol on an electronically braked bicycle ergometer (Rodby-Elema). The test consisted of three grades (0.5, 1 and 1.5 W/kg) of steady-state exercise, each lasting 3 to 4 minutes, depending on achievement of the steady-state. In some patients, where the third grade would pose a greater health risk or the intensity would be higher than the anaerobic threshold causing the exercise values no longer to be a "steady-state", only two grades were administered. After an adequate rest to full recovery, a modified continuous load-incremental exercise test ("ramping protocol") was conducted. The test was individually led from 0.4 - 0.5 W/kg with an increase of 4 - 6 W per 10 s in order to bring the patients to the maximal point in 4 to 5 minutes. The length of the ramping protocol was dictated by the fact that patients would not tolerate a longer protocol and it would involve more risk for them. The pedaling speed was maintained within the range of 60 to 70 rpm, according to the patient's preference. Patients were verbally encouraged to exercise until the point of exhaustion. To ensure maximal effort, the following criteria were met: Respiratory Exchange Ratio value higher than 1.05 and the inability to maintain a constant pedaling rate. Prior to the test and throughout the test, values for HR, blood pressure and electrocardiography (Siemens Mingocard) were recorded. Oxygen consumption (an Oxycon Beta Mijnhardt breath-by-breath gas exchange analyzer) was measured during the last minute of each grade and constantly throughout the "ramping protocol". A fifteen grade Borg's RPE scale (Borg 1998) in A3 format was in full view of the patients at all times. Patients were asked to estimate their effort at the end of each grade and at the end of the ramping protocol, during the 5 seconds after they finished the particular exercise.

All data were analyzed using non-parametric statistical techniques. Spearman Rank - Difference Correlation was used to describe the relationships and the Wilcoxon Paired Test was used for group comparisons. All levels of significance were established at p < 0.05.

All patients completed the first 2 grades of the GXT and 22 of them completed the third. RPE showed a linear increase with the increase in exercise intensity during the graded exercise test. The patients used the whole range of the scale, preferring odd numbers, which were verbally described. The mean values (SD) of RPE at each grade of the exercise test were: 8.61 (1.99) for an intensity of 0.5 W/kg, 12.52 (1.63) for an intensity of 1 W/kg and 16 (2.02) for an intensity equivalent to 1.5 W/kg. These RPEs differed significantly (p 0.01) from each other. At the end of the continuous maximal load-incremental test, the mean maximal power output was 1.89 (0.35) W/kg , whereas the subjective maximum was perceived at a RPE of 18.17 (1.42). Mean VO2max was 22.03 3.96.

The RPEs given by the patients during particular grades of GXT were correlated with objective physiological parameters. The relationship (as correlation coefficient) between RPE and % of VO2max was 0.8 (Figure 1), for RPE and % of VEmax it was 0.87 and for RPE and % of HRmax (computed according to Karvonen formula as: (HRexercise - HRrest ) x (HRmax - HRrest)-1 x 102) it was 0.82, all being statistically significant (p < 0.001). In terms of absolute values (i.e. for HR bpm etc.) those values dropped to: 0.71 (RPE - VO2 ), 0.75 (RPE - VE), and 0.73 (RPE - HR), again significant (p < 0.001). The relationship between objective physiological parameters only, HR and % of VO2max (Figure 1) and between HR and VO2 was 0.76 and 0.66 respectively (p < 0.001).

Figure 1: Relationship between RPE and % VO2max (r = 0.8), and between HR and % VO2max (r = 0.76)

For each individual, a score of extraversion was determined from the EPI questionnaire (B version) using a standard pattern of score rack (Miglierini and Vonkomer 1979). The extraversion scores ranged from 6 to 17. The mean score of extraversion in our group was 11.84 (2.65). The RPEs were correlated with the scores for extraversion, particularly for each grade of the test. A significant negative relationship between RPE and extraversion was found for all intensities. For a power output of 0.5 W/kg the correlation coefficient was -0.4, for 1 W/kg, r was -0.47 and for the last intensity -0.44 respectively (all p 0.05).

The results of our experiment confirm that the Borg's RPE scale may serve as an aid in exercise testing for individuals being treated with beta-blockers. High correlation coefficients (r = 0.8 - 0.87) between RPE and the objective physiological parameters expressed in relative terms of exercise intensity (i.e. % VO2max, % VEmax, % HRmax) obtained during graded exercise tests showed a strong positive linear relationship between subjective and objective assessments of exercise strain. These coefficients are at about the same level as reported e.g. Brodie et al. (1996): r = 0.79 - 0.89 in their study involving patients on beta-blockade. We found the highest correlation for ventilation, which is in accordance with the findings from a multiple regression study by Noble et al. (1973) showing ventilation to be the physiological variable most closely related to exertional perceptions in exercise up to 15 minutes. The linearly increasing growth function and high correlations between RPE and physiological variables across subjects were previously considered to prove a general validation of the scale (Borg 1998). Even though the correlation cannot be interchangeable with causality, a clear description of a close relationship can be seen. When absolute values of objective variables were used, correlations dropped to a lower level (r = 0.71 - 0.75), while still remaining significant. These results tally with Noble and Robertson (1996) and Borg (1998), who report that the relationship between discussed parameters is best described using the relative expressions of the strain. Also, it confirms the findings that the correlation values decrease with age and health problems (Borg 1998). Comparing the relationships of objective and subjective parameters to % VO2max which is considered to be the gold standard for exercise intensity measurement, the relationship for RPE is closer than for HR. However, although the correlations are quite high, as might be expected with this number of subjects, the question still remains whether the use of RPE independently of objective parameters is sufficient for us. At any rate, our results show that it is no worse a parameter than HR, which is mostly used.

Furthermore, the results show that the increase of 0.5 W/kg in exercise intensity was followed by an increase of about 4 grades in RPE in tested patients. This could provide important information for the exercise test progression and overall compliance with the testing procedures. However, it should also be noted that this value is rather general and may vary as a function of clinical condition and aerobic fitness.

As for the influence of personality factors, RPE was found to be significantly related to extraversion in a negative sense. The results thus suggest that, to some extent, the higher the patient's scores in extraversion, the lower his/her RPE and vice versa (i.e. extroverts tend to underrate work intensity). This tallies with previous findings by Morgan (1973; 1994), who conducted similar experiments on young healthy subjects, although with rather stronger relationships (r = -0.62 to -0.71), especially at higher workloads. In our experiment, the influence of extraversion was not so high. The relationship became slightly stronger at an intensity of 1 W/kg. On the other hand, a slight decrease in correlation for the last grade could be explained by the lower number of patients completing this grade. This is quite interesting, since some previous works concerning the psychological factors of RPE suggested that these factors are more salient at lower intensities (Noble & Robertson 1996; Borg 1998). Nevertheless, Watt and Grove (1993) suggested that the effect of psychosocial variables was not limited to lower and moderate intensities and this opinion might also be confirmed by our work. We suggest that a combination of factors has been at play, involving not only extraversion, but also the beta-blockade and its impact on exertion perceptions. Obviously, more factors play a role in perceived exertion and account for quite high variance which cannot be explained by physiological factors only and thus must certainly be kept in mind when using a subjective evaluation of exercise.

We found a significant positive relationship between RPE and objective physiological parameters confirming the usefulness of the RPE scale for cardiovascular patients on beta-blockade. The relationship of relatively expressed oxygen consumption with RPE seems to be closer than the relationship with HR. On the other hand, a significant negative relationship was found between RPE and extraversion, thus suggesting that RPE might be distorted by personality factors, not only in young healthy subjects but also in older cardiac patients. For clinical practice it means that RPE scale is a beneficial approach for monitoring exercise intensity in patients on beta-blockade, since it is a parameter no weaker than the conventionally used HR. However, personality and other psychological factors might be very important in perceived exertion probably in all age groups. For future studies, more interest should be expressed in psychological and social factors since they play a significant role in our perception.

Borg, G. (1998). Borg's Perceived exertion and pain scales. Champaign IL: Human Kinetics. [ISBN 0-88011-623-4].

Brodie, D.A., Odley, J., Bundred, P.E. & Salahuddin, M. (1996). Exercise heart rate - rating of perceived exertion relationships in patients using beta-blockade medication following myocardial infarction. Journal of Sport Science, 14, 67-68.

Eston, R. & Connolly, D. (1996). The use of Ratings of Perceived Exertion for exercise prescription in patients receiving beta-blocker therapy. Sports Medicine, 21, 176-190.

McArdle, W.D., Katch, F.I. & Katch, V.L. (1996). Exercise physiology: Energy, nutrition, and human performance. Baltimore: Williams and Wilkins. [ISBN 0-683-05731-6].

Miglierini, B. & Vonkomer, J. (1979). Eysenck Personality Inventory - a manual. Bratislava: Psychodiagnostické a didaktické testy.

Morgan, W.P. (1973). Psychological factors influencing perceived exertion. Medicine and Science in Sports and Exercise, 5, 97-103.

Morgan, W.P. (1994). Psychological components of effort sense. Medicine and Science in Sports and Exercise, 26, 1071-1077.

Noble, B.J., Metz, K.F., Pandolf, K.B. & Cafarelli, E. (1973). Perceptual responses to exercise: A multiple regression study. Medicine and Science in Sports and Exercise, 5, 104-109.

Noble, B.J. & Robertson, R. (1996). Perceived exertion. Champaign, IL: Human Kinetics. [ISBN 0-88011-508-4].

Szabo, A. (1992). Habitual participation in exercise and personality. Perceptual and Motor Skills, 74, 978.

Vanhees, L., Fagard, R. & Amery, A. (1982). Influence of beta-adrenergic blockade on effects of training in patients with ischaemic heart disease. British Heart Journal, 48, 33-38.

Watt, B. & Grove, R. (1993). Perceived exertion. Antecedents and Applications. Sports Medicine, 15, 225-241.

Wise, T.N. (1995). The physician - patient relationship. In J.M. Wiener & N.A. Breslin (Eds.), The behavioral sciences in psychiatry (pp. 189-201). Baltimore: Williams and Wilkins.


BRIEF COMMUNICATION Rating of perceived exertion, physiological parameters and extraversion in patients treated with beta-blockers Klára Mocková, Jirí Radvanský Affiliations: Klára Mocková (biography) Charles University 2nd Medical faculty - Dept. of Sports Medicine V Úvalu 84 150 06 Prague 5 Czech Republic Tel.: +420224435510 Fax.: +420222718637 e-mail: klara.mockova@lfmotol.cuni.cz Jirí Radvanský Charles University 2nd Medical faculty - Dept. of Sports Medicine V Úvalu 84 150 06 Prague 5 Czech Republic Rating of perceived exertion, physiological parameters and extraversion in patients treated with beta-blockers Introduction In terms of adapted physical activities we promote a variety of therapeutic, preventive and recreational exercises. For optimal exercise prescription, frequency, duration and intensity determination is crucial. In terms of intensity, this must be clearly determined in order to produce the desired improvements, but also to ensure that the individual is not overstrained and harmed (Mc Ardle et al. 1996). Heart rate (HR) is the most frequently used indicator of exercise intensity. However, in the clinical practice of exercise prescription some problems may exist with the accurate use of HR caused by arrhytmias and impaired exercise HR acceleration due to ischaemic heart disease, specifically in an elderly population. The use of HR is rather dubious especially in the home and in during recreational activities. Also, its use in patients being treated with beta-blockers (i.e. patients with abnormal HR exercise reaction) is rather complicated, since the resulting heart rate is a function of at least those variables: an exercise type/intensity and drug level. Even if it could be shown that cardiac patients on beta-blockade had similar improvements after the training programme compared to non-blockade, and HR still seems to be a reliable parameter (Vanhees et al. 1982), the problem remains of changing HR according to time and dosage of the medication. Hence, Borg's Rating of Perceived Exertion (RPE) was suggested (Eston and Connolly 1996) for use in exercise testing and therapy. In addition to its noninvasiveness, low cost and simplicity, it has many advantages for field exercise, and it helps to dose the exercise intensity according to a patient's actual state of health. RPEs are frequently used as part of standard response measurements during graded exercise testing (GXT). Such assessment should provide a good starting point for exercise therapy, where RPEs may be used to control the exercise intensity. One of the aims of this study was therefore to explore whether RPE is a good indicator of physical strain during GXT in cardiovascular patients on beta-blockade in the relationship to "objective" physiological parameters. According to basic understanding of the perceived exertion as stated by Borg (1998) and Noble and Robertson (1996), the sense of effort is seen as a kind of "Gestalt" and a complex psycho-physiological process that brings together a number of exertional symptoms. It was suggested earlier that RPE is influenced by psychological factors (Morgan 1973; 1994) including temperament characteristics as part of human personality descriptors. Since it was shown that personality traits are related to habitual participation in physical exercise, for example, (Szabo 1992), it might be of interest to explore the relationship between those factors and perceived exertion in populations where exercise and physical activity is considered to be a cornerstone of lifestyle as a primary or secondary means of prevention of so-called physiological disorders. Extraversion, as one of the personality dimensions, refers to such traits described as active, assertive, carefree, dominant, lively, venturesome and sociable (Wise 1995). Extroverts probably need greater sensory stimulation in order to experience a certain level of perception in comparison with introverts. The influence of extraversion on perceived exertion was previously reported in a pilot study by Morgan (1973, 1994). His results opened up the concept of personality factors, showing both the relationship and links to preferred exertion. Our question was whether similar relationships persist in a population of elderly people with cardiovascular disorders. Materials and Methods Eighteen female and thirteen male patients treated with selective beta-blockers (or a combination of drugs involving a beta-blocking agent) as a result of ischaemic heart disease and/or hypertension participated in this study (age = 61.1 8.58, BMI = 28.44 4.31). None of the subjects suffered from any disorder which is known to have a possible significant influence on perceived exertion. Inclusion criteria were: under 80 years of age, stabilized on any beta-blocking therapy, belonging to the Weber A-B classification and sedentary (patients reported they had not participated in any form of aerobic conditioning within the last year). Patients were instructed to refrain from any additional exercise, alcohol, smoking and heavy stress for 24 hours before the exercise test. Firstly, patients completed questionnaires concerning medical history and the Eysenck Personality Inventory (EPI). The EPI consists of 57 closed (yes/no) questions. Its reliability in retesting, as reported by previous studies, was 0.85 and its validity was confirmed by comparison with the Maudsley Personality Inventory (Miglierini and Vonkomer 1979). The subjects then read the RPE scale with standardized instructions (Borg 1998), which were both translated into Czech. Each patient performed one graded exercise test (GXT) protocol on an electronically braked bicycle ergometer (Rodby-Elema). The test consisted of three grades (0.5, 1 and 1.5 W/kg) of steady-state exercise, each lasting 3 to 4 minutes, depending on achievement of the steady-state. In some patients, where the third grade would pose a greater health risk or the intensity would be higher than the anaerobic threshold causing the exercise values no longer to be a "steady-state", only two grades were administered. After an adequate rest to full recovery, a modified continuous load-incremental exercise test ("ramping protocol") was conducted. The test was individually led from 0.4 - 0.5 W/kg with an increase of 4 - 6 W per 10 s in order to bring the patients to the maximal point in 4 to 5 minutes. The length of the ramping protocol was dictated by the fact that patients would not tolerate a longer protocol and it would involve more risk for them. The pedaling speed was maintained within the range of 60 to 70 rpm, according to the patient's preference. Patients were verbally encouraged to exercise until the point of exhaustion. To ensure maximal effort, the following criteria were met: Respiratory Exchange Ratio value higher than 1.05 and the inability to maintain a constant pedaling rate. Prior to the test and throughout the test, values for HR, blood pressure and electrocardiography (Siemens Mingocard) were recorded. Oxygen consumption (an Oxycon Beta Mijnhardt breath-by-breath gas exchange analyzer) was measured during the last minute of each grade and constantly throughout the "ramping protocol". A fifteen grade Borg's RPE scale (Borg 1998) in A3 format was in full view of the patients at all times. Patients were asked to estimate their effort at the end of each grade and at the end of the ramping protocol, during the 5 seconds after they finished the particular exercise. All data were analyzed using non-parametric statistical techniques. Spearman Rank - Difference Correlation was used to describe the relationships and the Wilcoxon Paired Test was used for group comparisons. All levels of significance were established at p < 0.05. Results All patients completed the first 2 grades of the GXT and 22 of them completed the third. RPE showed a linear increase with the increase in exercise intensity during the graded exercise test. The patients used the whole range of the scale, preferring odd numbers, which were verbally described. The mean values (SD) of RPE at each grade of the exercise test were: 8.61 (1.99) for an intensity of 0.5 W/kg, 12.52 (1.63) for an intensity of 1 W/kg and 16 (2.02) for an intensity equivalent to 1.5 W/kg. These RPEs differed significantly (p 0.01) from each other. At the end of the continuous maximal load-incremental test, the mean maximal power output was 1.89 (0.35) W/kg , whereas the subjective maximum was perceived at a RPE of 18.17 (1.42). Mean VO2max was 22.03 3.96. The RPEs given by the patients during particular grades of GXT were correlated with objective physiological parameters. The relationship (as correlation coefficient) between RPE and % of VO2max was 0.8 (Figure 1), for RPE and % of VEmax it was 0.87 and for RPE and % of HRmax (computed according to Karvonen formula as: (HRexercise - HRrest ) x (HRmax - HRrest)-1 x 102) it was 0.82, all being statistically significant (p < 0.001). In terms of absolute values (i.e. for HR bpm etc.) those values dropped to: 0.71 (RPE - VO2 ), 0.75 (RPE - VE), and 0.73 (RPE - HR), again significant (p < 0.001). The relationship between objective physiological parameters only, HR and % of VO2max (Figure 1) and between HR and VO2 was 0.76 and 0.66 respectively (p < 0.001). Figure 1: Relationship between RPE and % VO2max (r = 0.8), and between HR and % VO2max (r = 0.76) For each individual, a score of extraversion was determined from the EPI questionnaire (B version) using a standard pattern of score rack (Miglierini and Vonkomer 1979). The extraversion scores ranged from 6 to 17. The mean score of extraversion in our group was 11.84 (2.65). The RPEs were correlated with the scores for extraversion, particularly for each grade of the test. A significant negative relationship between RPE and extraversion was found for all intensities. For a power output of 0.5 W/kg the correlation coefficient was -0.4, for 1 W/kg, r was -0.47 and for the last intensity -0.44 respectively (all p 0.05). Discussion The results of our experiment confirm that the Borg's RPE scale may serve as an aid in exercise testing for individuals being treated with beta-blockers. High correlation coefficients (r = 0.8 - 0.87) between RPE and the objective physiological parameters expressed in relative terms of exercise intensity (i.e. % VO2max, % VEmax, % HRmax) obtained during graded exercise tests showed a strong positive linear relationship between subjective and objective assessments of exercise strain. These coefficients are at about the same level as reported e.g. Brodie et al. (1996): r = 0.79 - 0.89 in their study involving patients on beta-blockade. We found the highest correlation for ventilation, which is in accordance with the findings from a multiple regression study by Noble et al. (1973) showing ventilation to be the physiological variable most closely related to exertional perceptions in exercise up to 15 minutes. The linearly increasing growth function and high correlations between RPE and physiological variables across subjects were previously considered to prove a general validation of the scale (Borg 1998). Even though the correlation cannot be interchangeable with causality, a clear description of a close relationship can be seen. When absolute values of objective variables were used, correlations dropped to a lower level (r = 0.71 - 0.75), while still remaining significant. These results tally with Noble and Robertson (1996) and Borg (1998), who report that the relationship between discussed parameters is best described using the relative expressions of the strain. Also, it confirms the findings that the correlation values decrease with age and health problems (Borg 1998). Comparing the relationships of objective and subjective parameters to % VO2max which is considered to be the gold standard for exercise intensity measurement, the relationship for RPE is closer than for HR. However, although the correlations are quite high, as might be expected with this number of subjects, the question still remains whether the use of RPE independently of objective parameters is sufficient for us. At any rate, our results show that it is no worse a parameter than HR, which is mostly used. Furthermore, the results show that the increase of 0.5 W/kg in exercise intensity was followed by an increase of about 4 grades in RPE in tested patients. This could provide important information for the exercise test progression and overall compliance with the testing procedures. However, it should also be noted that this value is rather general and may vary as a function of clinical condition and aerobic fitness. As for the influence of personality factors, RPE was found to be significantly related to extraversion in a negative sense. The results thus suggest that, to some extent, the higher the patient's scores in extraversion, the lower his/her RPE and vice versa (i.e. extroverts tend to underrate work intensity). This tallies with previous findings by Morgan (1973; 1994), who conducted similar experiments on young healthy subjects, although with rather stronger relationships (r = -0.62 to -0.71), especially at higher workloads. In our experiment, the influence of extraversion was not so high. The relationship became slightly stronger at an intensity of 1 W/kg. On the other hand, a slight decrease in correlation for the last grade could be explained by the lower number of patients completing this grade. This is quite interesting, since some previous works concerning the psychological factors of RPE suggested that these factors are more salient at lower intensities (Noble & Robertson 1996; Borg 1998). Nevertheless, Watt and Grove (1993) suggested that the effect of psychosocial variables was not limited to lower and moderate intensities and this opinion might also be confirmed by our work. We suggest that a combination of factors has been at play, involving not only extraversion, but also the beta-blockade and its impact on exertion perceptions. Obviously, more factors play a role in perceived exertion and account for quite high variance which cannot be explained by physiological factors only and thus must certainly be kept in mind when using a subjective evaluation of exercise. Conclusions We found a significant positive relationship between RPE and objective physiological parameters confirming the usefulness of the RPE scale for cardiovascular patients on beta-blockade. The relationship of relatively expressed oxygen consumption with RPE seems to be closer than the relationship with HR. On the other hand, a significant negative relationship was found between RPE and extraversion, thus suggesting that RPE might be distorted by personality factors, not only in young healthy subjects but also in older cardiac patients. For clinical practice it means that RPE scale is a beneficial approach for monitoring exercise intensity in patients on beta-blockade, since it is a parameter no weaker than the conventionally used HR. However, personality and other psychological factors might be very important in perceived exertion probably in all age groups. For future studies, more interest should be expressed in psychological and social factors since they play a significant role in our perception. References Borg, G. (1998). Borg's Perceived exertion and pain scales. Champaign IL: Human Kinetics. [ISBN 0-88011-623-4]. Brodie, D.A., Odley, J., Bundred, P.E. & Salahuddin, M. (1996). Exercise heart rate - rating of perceived exertion relationships in patients using beta-blockade medication following myocardial infarction. Journal of Sport Science, 14, 67-68. Eston, R. & Connolly, D. (1996). The use of Ratings of Perceived Exertion for exercise prescription in patients receiving beta-blocker therapy. Sports Medicine, 21, 176-190. McArdle, W.D., Katch, F.I. & Katch, V.L. (1996). Exercise physiology: Energy, nutrition, and human performance. Baltimore: Williams and Wilkins. [ISBN 0-683-05731-6]. Miglierini, B. & Vonkomer, J. (1979). Eysenck Personality Inventory - a manual. Bratislava: Psychodiagnostické a didaktické testy. Morgan, W.P. (1973). Psychological factors influencing perceived exertion. Medicine and Science in Sports and Exercise, 5, 97-103. Morgan, W.P. (1994). Psychological components of effort sense. Medicine and Science in Sports and Exercise, 26, 1071-1077. Noble, B.J., Metz, K.F., Pandolf, K.B. & Cafarelli, E. (1973). Perceptual responses to exercise: A multiple regression study. Medicine and Science in Sports and Exercise, 5, 104-109. Noble, B.J. & Robertson, R. (1996). Perceived exertion. Champaign, IL: Human Kinetics. [ISBN 0-88011-508-4]. Szabo, A. (1992). Habitual participation in exercise and personality. Perceptual and Motor Skills, 74, 978. Vanhees, L., Fagard, R. & Amery, A. (1982). Influence of beta-adrenergic blockade on effects of training in patients with ischaemic heart disease. British Heart Journal, 48, 33-38. Watt, B. & Grove, R. (1993). Perceived exertion. Antecedents and Applications. Sports Medicine, 15, 225-241. Wise, T.N. (1995). The physician - patient relationship. In J.M. Wiener & N.A. Breslin (Eds.), The behavioral sciences in psychiatry (pp. 189-201). Baltimore: Williams and Wilkins.
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