Ratings of perceived exertion by women with internal or external locus of control
Peter Hassmen
According to the range theory proposed by Borg (1961, 1962), all individuals have about the same perceptual range from minimal to maximal subjective intensity, although their physical working capacity may differ significantly. This means, for example, that all persons working at their maximum capability will experience approximately the same level of perceived effort or exertion. One commonly used method for estimating perceived exertion is the 15-point Ratings of Perceived Exertion Scale (RPE; Borg, 1970, 1985). RPE responses have been shown to be valid and highly reliable, with higher coefficients (Pearson product-moment correlation formula) reported for progressive ([r.sub.xy] = .80) than random presentation ([r.sub.xy] = .78) of exercise intensities and for terminal ([r.sub.xy] = .90) rather than intermediate ([r.sub.xy] = .76) ratings (Skinner, Hutsler, Bergsteinova, & Buskirk, 1973; Stamford, 1976).
The range of the RPE is from 6 to 20, which is approximately analogous to a heart-rate (HR) range of 60 to 200 b [center dot] [min.sup.-1]. Thus, during physical exercise, an individual with a HR of 150 b [center dot] [min.sup.-1] should rate his or her perceived exertion as about 15 on the RPE scale. This relationship may be altered, however, by such factors as age, type of exercise, environment, certain drugs, and anxiety (Borg, 1982; Borg, Hassmen, & Lagerstrom, 1987; Ekblom, & Goldbarg, 1971; Hassmen, 1990; Pandolf, Cafarelli, Noble, & Metz, 1972).
Other factors may also be responsible for differences in RPE between individuals. Both psychological and physiological modifiers have been found to influence these ratings and thereby cause variance in RPE, both between and within individuals (Hassmen, 1991, 1995; Morgan, 1973; Pandolf, 1983; Watt & Grove, 1993). Based on the findings of experiments carried out in controlled laboratory settings, researchers have suggested that approximately two thirds of the variance in RPE may be accounted for by various physiological responses (Morgan, 1973; Noble, Metz, Pandolf, & Cafarelli, 1973). The remaining unexplained variance might be related to factors of a psychological nature, such as personality, behavior pattern, and cognitive style (Morgan, 1973). However, the physiological responses may not influence the perception of effort to as great an extent in field situations, where a diversity of social psychological factors influence the performance of the individual (Rejeski, 1981). The psychological modifiers might then explain a proportionally larger share of the variance in RPE, and it may be of importance to consider not only what the individuals are doing but also what they think and feel that they are doing (Morgan, 1973). What psychological variables might then be correlated with ratings of perceived exertion?
It has been suggested that gender and gender-based schematic processing influence the ratings of perceived exertion to some extent (Hochstetler, Rejeski, & Best, 1985; Sidney, & Shephard, 1977; Wrisberg, Franks, Birdwell, & High, 1988). Other studies, however, have not been able to detect any gender differences (O’Connor, Morgan, & Raglin, 1991; Sylva, Byrd, & Mangum, 1990). The athletic experience of a person has been shown to mediate the ratings somewhat (Winborn, Meyers, & Mulling, 1988), which could account for some of the differences between men and women, because women often have insufficient past athletic experience (Rejeski, 1981). The latter suggestion is also a possible explanation of why O’Connor et al. and Sylva et al. did not find differences between men and women in RPE: All participants in those studies were elite athletes, and thus both men and women were very experienced with physical exertion.
Motivation to do physical work as well as task aversion could be additional psychological factors that might explain differences between individuals. If a person is less motivated, the exertion might feel heavier and more stressful than when the person feels highly motivated to perform physically (Hochstetler, Rejeski, & Best, 1985: Kinsman, Weiser, & Stamper, 1973). Other psychological modifiers that might influence the rating behavior are the behavior patterns and the personality of the individual. Type A behavior, anxiety, extraversion/introversion and neuroticism/stability, depression, and somatic perception have been shown to explain some of the differences in ratings of perceived exertion (Hassmen, Stahl, & Borg, 1993; Morgan, 1973).
It is reasonable to assume that other personality variables might influence the experience of physical exertion as well. The concept of reinforcement control has emerged from the theory of social learning (Rotter, 1954). Rotter (1966) further developed the concept of internal-external control (i.e., “locus of control”) and devised a scale to differentiate individuals with an external locus of control from those with an internal locus of control. An individual who has a belief in external control perceives reinforcement as a result of chance or fate, under the control of powerful “others” or strong, uncontrollable forces. On the other hand, a person who perceives reinforcement as contingent upon personal characteristics and his or her own behavior is categorized as having an internal locus of control.
Several studies have shown that the belief in internal or external control might be related to an individual’s ability to monitor and alter particular physiological responses (Gosling, May, Lavond, Barnes, & Carreira, 1974; Heffernan-Colman, Sharpley, & King, 1992; Ray, 1974; Wagner, Bourgeois, Levenson, & Denton, 1974). The diverse physiological responses to stimulus conditions of individuals with internal and external loci of control were also demonstrated by Berggren, Ohman, and Fredriksson (1977), who came to the conclusion that externals have poorer control of attention than internals. Individuals with an external locus of control did not appear to be able to differentiate between relevant and irrelevant cues to the same extent as individuals with an internal locus of control. These results are not surprising, given the fact that previous research has shown that internals, as compared with externals, seem to acquire more information and use the information more adequately and independently, pay more attention to relevant information, and also seem to be able to dismiss the irrelevant cues in the situation at hand (e.g., Phares, 1976).
It has been suggested that to gain a more substantial structure for social psychological inquiry, an information-processing approach, stressing the active dimension of perception, is needed (Rejeski, 1985). Viewing perception not as a passive but as an active process – that is, making an assumption that sensory cues for perceived exertion interact with psychological factors before perception and that cognition and emotion have a mediating effect on the conscious recognition of exertional cues – might further explain some of the variance of the ratings of perceived exertion (cf. Hassmen, 1991). If one regards perception as an active process and agrees that an information-processing model helps to understand variations in RPE, then one might detect differences in RPE between individuals with different information-processing abilities. The poorer information-processing abilities of individuals with external locus of control, compared with internals, could influence the ratings of perceived exertion, with internals being more accurate in their ratings. Our aim in this study, then, was to examine a group of women for possible effects of an internal versus external locus of control on the ratings of perceived exertion during physical exercise.
Method
Participants
The participants were 50 female Stockholm University psychology students, mean age 25.7 years (SD = 4.4). They participated in the experiment in partial fulfillment of their course requirements.
Apparatus and Material
We used an electronically braked cycle ergometer (Elema Schonander, EM 361:2) and a Sporttester (PE 3000) to register the HRs. Ratings of perceived exertion were made on the RPE scale developed by Borg (1970, 1985), with end points to indicate minimal and maximal effort.
To differentiate between individuals with internal and external loci of control, we used the Rotter Internal-External Control Scale. The Rotter I-E Control Scale is a forced-choice scale consisting of 29 items, including 6 filler items. A median split is used most often to categorize the individuals as externals or internals (Rotter, 1966). Thus, we classified those above the median as having an external locus of control (n = 25) and those below the median as having an internal locus of control (n = 25). For the present sample, the mean, median, and standard deviation were 9.5, 9.5, and 3.2, respectively.
Procedure
The purpose of the study was not explained to the participants until afterward, but they were informed that they were going to work on an ergometer cycle for 16 min and complete some questionnaires. Before starting the experiment, we asked all participants about their feelings about participating in the study, to check differences in ratings of perceived exertion related to different motivations. All reported being positive and interested. Furthermore, the participants were asked about their athletic experience before the study. Their answers indicated that almost all were sedentary. A few in each group performed regular physical exercise (jogging, aerobics), but none could by any means be considered an elite athlete.
The participants started with the questionnaires and then did the cycling. They were told to pedal at a rate of 60 rev [center dot] [min.sup.-1]. The participants cycled for 4 min at each of four increasing power levels. HR was recorded at each level after 3 min, 45 s, whereupon participants were asked to give their overall rating of perceived exertion on the RPE scale. Before the cycling, the participants were given standardized instructions on how to use the RPE scale.
Calculations and Statistical Analyses
Each individual’s RPE at an HR of 150 b [center dot] [min.sup.-1] (subsequently referred to as [RPE.sub.150]) was calculated by fitting a straight regression line to the individual HR-RPE data. We then performed a Student’s t test for unpaired observations, with locus of control (group: internal-external) as the independent variable and the calculated RPE at a HR of 150 as the dependent variable. We also performed a similar analysis, using each individual’s HR at an RPE of 15 (i.e., [HR.sub.15]) as the dependent variable and group as the independent variable.
We also calculated a ratio between HR and RPE for each of the four different power levels, to examine possible differences in rating behavior at different levels of physical effort. This was done in line with Borg’s notion (1970) that the relationship between HR and RPE is close to 10:1 for healthy individuals who are not too old. Thus, a ratio of 10 would be taken to indicate a correct rating, whereas a ratio greater than 10 would be obtained when the individuals rated their perceived exertion relatively lower than their corresponding HR (“underestimation”). A ratio below 10 would be obtained when the individuals rated their perceived exertion relatively higher than their HR (“overestimation”). We performed a two-way analysis of variance (ANOVA), with locus of control as the independent variable and the different times of measurement (i.e., the four different power levels) as the dependent and repeated measurement, on these data, to detect differences between the two groups.
To detect possible differences between the groups in physical working capacity, we estimated [VO.sub.2 max/kg] (in ml [center dot] [min.sup.-1] [center dot] [kg.sup.-1]) according to tables by Astrand (1960) and Astrand and Rhyming (1954). For all statistical analyses, we regarded differences as significant at a probability level of p [less than] .05.
Results
Descriptive data for the two groups and for the groups combined are shown in Table 1. We observed no significant differences between the participants in the external group and those in the internal group.
The t test performed on the [RPE.sub.150] data (i.e., RPE at a HR of 150 b [center dot] [min-1]) proved to be statistically significant (t = 4.12, p [less than] .001, df = 48). The externals rated their exertion (M = 16.2, SD = 1.6) higher than the internals did theirs (M = 14.6, SD = 1.2). If a population mean of 15 is assumed to be a correct value (for reasons given in the introduction of this article) and this value is used as the population mean in the statistical analyses, the externals’ value of 16.2 differs significantly (t = 3.74, p [less than] .01, df = 24) from 15, whereas the internals’ value of 14.6 does not.
[TABULAR DATA FOR TABLE 1 OMITTED]
The subsequent t test, performed on the HR15 data (HR at an RPE of 15) also revealed a significant difference, t(48) = 3.59, p [less than] .001, between the internals (M = 153.1, SD = 12.6) and the externals (M = 140.1, SD = 13.0). Again, if a population mean of 150 is assumed to be a correct value, the externals’ value of 140.1 was significantly different from 150, t(24) = -3.82, p [less than] .001, whereas the internals’ value of 153.1 was not.
With the HRs and RPEs expressed as ratios (HR/RPE) at the four different levels of work load, the two-way ANOVA with repeated measures on the second factor showed a significant main effect of work load, F(3, 144) = 4.70, p [less than] .01, and of group, F(1, 48) = 6.10, p [less than] .02. Moreover, the interaction between work load and locus of control (i.e., group) was significant, F(3, 144) = 2.72, p [less than] .05. Although the two groups did not differ much initially, we detected considerably larger discrepancies at the heavier work loads [ILLUSTRATION FOR FIGURE 1 OMITTED]. To detect exactly where the differences became statistically significant, we performed pairwise t tests post hoc. To protect those analyses from the increased risk of Type I errors (because of the performance of four t tests), we followed the Bonferroni procedure. Hence, the new critical limit was set at .0125 (i.e., .05/4). The analyses indicated that the groups did not differ significantly at the first or second work load. Differences were found, however, at the third, t(48) = 3.56, p [less than] .001, and fourth, t(48) = 3.51, p [less than] .01, work loads.
Discussion
Our main finding in the present study was that women with an external locus of control rated their perceived exertion in a fairly similar way to that of women with an internal locus of control at low work loads, but the groups differed at higher work loads. Specifically, at the third and fourth work load, we found the ratings of the two groups to be significantly different [ILLUSTRATION FOR FIGURE 1 OMITTED]. This was further shown by the analyses of the [RPE.sub.150] and [HR.sub.15] data, which indicated significant differences throughout between the externals and the internals. Thus, actual dissimilarities in rating behavior seem to exist between internals and externals, especially at heavier work loads, at least when cycling is performed on an ergometer cycle. Even larger discrepancies might have been found between the two groups if the work loads had been even heavier, thereby resulting in higher HRs and RPEs. On the other hand, heavier work loads might have resulted in ceiling effects – that is, participants might have reached levels of exertion close to ratings of 19-20, thereby eliminating possible differences found below that level. Similarly, work loads resulting in HRs above 170 b [center dot] [min.sup.-1] or ratings above 17 on the RPE scale might produce lactic acid in some individuals but not in others; thus, high but not excessively high levels are preferable for a comparison on equal terms.
Assuming that perception is regarded as an active process (e.g., Rejeski, 1985), the relatively small differences between the groups at low work loads would be expected, because for obvious reasons, less information is available for processing. If individuals with an internal locus of control have a greater information-processing ability than those with an external locus of control (Phares, 1976), differences should emerge when more information is available for processing. With increasing work loads, more information becomes available for processing – for example, cues emanate from increased muscular strain, heightened HR, perspiration, and increased respiratory rate (Hassmen, 1991; Noble, Kraemer, Allen, Plank, & Woodard, 1986; Pandolf, 1986; Robertson, 1982). Logically, then, individuals differing in locus of control should differ more at high work loads than at low work loads. That seems to have been the case in the present study.
It has been suggested that there are two major categories of physiological factors that contribute to the perception of effort: a local factor related to sensations of strain in the exercising muscles or joints and a central factor related primarily to sensations from the cardiopulmonary system (Borg, 1962; Ekblom, & Goldbarg, 1971). However, an accentuation of a particular factor or physiological cue by an elevated rate, concentration, or value can dominate the overall rating of perceived exertion. Local factors seem to dominate when small-muscle groups are active, whereas work with large-muscle groups seem to stress the pulmonary ventilation and the circulation, thereby adding to the local strain (Ekblom & Goldbarg, 1971; Kinsman, & Weiser, 1976; Pandolf, 1977). It also has been suggested by Cafarelli and Noble (1976) that during cycling, individuals rate local effort as more intense when local effort and central effort are rated separately.
The participants in the present study were instructed to rate their overall perceived exertion. But to rate their overall effort, individuals have to process information concerning sensations of the strain in the muscles or joints as well as from the cardiopulmonary system and thereafter integrate the information concerning these sensations. This necessary sequence of processing could be a factor that results in the differences in ratings of perceived exertion between those with an internal locus of control and those with an external one. Because of their alleged inferior information-processing abilities, individuals with an external locus of control might not be capable of processing the information correctly, or they may not be able to process the right information concerning the two factors and then integrate it to make a “correct” rating. It might also be that compared with internals, externals use information from only one factor to facilitate information processing, thus neglecting the other factor or weighting it differently. However, we did not make comparisons between local and central factors and further comparisons with the overall exertion in this study, so these questions will remain unanswered until further investigations are made.
Our results are, however, in line with research dealing with pain. Participants with an external locus of control have reported higher levels of pain and greater dissatisfaction with analgesia than internals have (Johnson, Magnani, Chan, & Ferrante, 1989). Similar results were presented by Bates and Rankin-Hill (1994), who suggested that “an increased sense of control may contribute to an increased ability to cope successfully with the chronic pain experience” (Bates & Rankin-Hill, 1994, p. 629). Even though pain and physical exertion are different perceptions, the same factors that cause externals to experience higher levels of pain than internals may contribute to the finding that externals overestimate their exertion, in comparison with internals.
Examining differences in ratings of perceived exertion in individuals with an internal or external locus of control – that is, individuals who, among other things, differ in information-processing capabilities and perhaps also use different strategies – could help to further understand the process of perception and subjective ratings of effort. Therefore, further studies should consider ratings of perceived exertion in individuals with internal and external loci of control, with ratings of both “local” and “central” feelings of strain and comparing different types of physical work. It would also be worthwhile to compare the results for men and women and to consider the increasing bulk of research dealing with self-efficacy (Bandura, 1992) and explanatory style (Seligman, 1992) – concepts that, together with locus of control, manifest a common interest in the extent to which people expect an outcome to be contingent on their own behavior (see also Peterson, & Stunkard, 1992). However, future research must take into consideration the warning, issued by Rotter (1990), that “the tendency to use new terms for old concepts” (p. 492) be avoided (see also Rotter, 1992).
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