Environmental effects on the ratings of perceived exertion in males and females.
The overall rating of perceived exertion is thought of as representing a kind of "gestalt" that is, an individual's integration of a great number of sensations (Borg, 1962). Important contributors are, to name a few, heart rate, ventilation, blood lactate, and oxygen consumption. Interestingly, correlations between heart rate (HR) and RPE often exceed 0.85 (Borg, 1962; Pandolf, 1983). The high consistency between HRs and RPEs also led Borg (1970, p. 93) to state: "As a rough approximation the heart rate for middle-aged people should, for work loads of medium intensity levels, be fairly close to 10 times the RPE-values", hence, a HR to RPE ratio of approximately 10:1 can be expected for work performed on a cycle ergometer.
It has, however, been pointed out that even if all physiological variables available are added together, only about two thirds of the total variance in RPE can still be explained. The remaining one third can instead be attributed to factors such as personality, behavior pattern, cognitive style, and motivation (Morgan, 1973; Noble, Metz, Pandolf, & Cafarelli, 1973). In addition to the above mentioned factors, or modifiers of perceived exertion (cf., Hassmen, 1995), a number of other components have been suggested to influence the exercise response.
The significance of the physical environment itself for RPEs was highlighted in a study by Ceci and Hassmen (1991) in which a group of middle-aged males ran either on a treadmill in a laboratory or outdoors in the field. The difference in perceived exertion between laboratory and field running was about two RPE-units. Explicitly, subjects perceived running in the field to be significantly less straining than running in the laboratory at the same relative HR and blood lactate levels. Given that the laboratory can be considered a less stimulating place than an outdoor running path, results similar to these have previously been described. Nethery, Harmer, and Taaffe (1991), for example, observed that exercise related RPEs were higher in a deprived sensory condition, followed by control and video conditions whereas the least exertion was perceived when the exercise was performed to music. The explanation offered was that the use of pleasant externally originating stimuli made it possible for the subjects to dissociate from the exercise-induced strain. Thus, the more pleasant stimuli, the less exertion perceived. In an earlier study, Pennebaker and Lightner (1980) tried to actively manipulate the attentional focus of their subjects, similar results emerged: subjects who listened to their own breathing during performance (self-focus) reported higher degrees of fatigue than subjects who heard distracting street sounds (external focus). Even though Morgan and Pollock (1977) never manipulated the attentional focus of their subjects, they nevertheless describe differences between nonelite distance runners, who used a dissociative cognitive strategy (i.e., external focus), in contrast to elite runners who instead used an associative strategy (self-focus). Accordingly, to adopt an external focus while exercising might be beneficial to most people (except elite athletes) in order to prolong and possibly enhance the benefits of exercise (cf., Wrisberg, Franks, Birdwell, & High, 1988).
A conclusion reached by Winborn, Meyers, and Mulling (1988), who investigated the influence of gender and prior athletic experience during ergometer cycling in a laboratory, was that the individual's past athletic experience was more important than the potential influence of gender. Despite the failure to detect any significant main effects of gender, the authors nevertheless found that males were generally more accurate in their RPEs than were women. High athletic experience males were more accurate than high athletic experience females, and low athletic experience females were the least accurate followed by low athletic experience males. The importance of previous athletic experience was also attested to by Rejeski (1981, p. 313), who wrote that: "RPE for a given task is, at least in part, a function of past experience." This inference was based on the observation that women reported lower RPEs as compared to men while exercising at the same relative intensity, and that these women had limited past experience. Consequently, it was concluded that the females possibly lacked in ability to accurately process effort sensations and feelings of fatigue.
Hence, if prior athletic experience can explain the alleged difference in rating behavior between females and males, then it can be predicted that groups equal in prior athletic experience should display only small differences. In addition, exercise performed in the laboratory should be perceived as more straining than exercise performed in a more stimulating environment (i.e., in the field). Presumably this should be valid for both females and males.
Thus, the purpose of the present study was to determine whether the rating behavior of females and males are comparable regardless of whether the exercise is performed in the laboratory or outdoors in the field (the latter supposedly leading to a higher degree of external focus as compared to the controlled laboratory condition).
A total of 24 females and 24 males volunteered to participate in the present study. Care was taken to ensure that the two groups were equal in respect to their prior or present participation in regular physical activity. Thus, one third of the subjects in each group were presently not physically active, neither were they allowed to have been physically active on a regular base previously. An additional one third were, and had been for at least a year, physically active on a moderate exercise-for-fitness level (two to four times per week) while the remaining one third performed straining aerobic exercise more than four but less than six times per week (three males and two females also participated regularly in running competitions). For a physical description, including cardiorespiratory data, see Table 1.
[TABULAR DATA FOR TABLE 1 OMITTED]
The cycling part was performed on an electronically braked cycle ergometer (Elema Schonander, EM 369:1). HR was registered, during both the cycle ergometer part and the run part, using a Sporttester PE 3000. Ratings of perceived exertion (RPE) were made on the 15-graded (6-20) RPE-scale by Borg (1970). Subjects were given standardized instructions as devised by Borg (1985). Furthermore, they were instructed to rate their overall degree of perceived exertion, trying to integrate all sensations coming from the body.
The complete test session, which was performed individually at separate occasions by all subjects, consisted of: (1) an ergometer cycle test; and (2) an outdoor run test. Before the test session commenced, standardized instructions were given and a written informed consent obtained. To rule out possible confounding factors, care was taken to ensure that the testings took place under approximately the same conditions for the males and females respectively (that is; time of day, temperature, humidity, etc.).
After a five minute warm up, on either 25 W (females) or 50 W (males), the subjects started to cycle on one of two cumulative work loads for five minutes each. These loads were chosen so that the subjects would reach HRs between 130 and 170 b-[min.sup.-1], in order to be able to estimate their maximal oxygen uptake (according to tables by Astrand & Ryhming, 1954; Astrarid, 1960). Thus, the work loads chosen for the females were 75 and 125 W, and for the males 100 and 200 W.
After a rest period of 20 minutes, the subjects proceeded with the run part. This took place on a level outdoor park path, with a length of 800 meters, and with the start and finish located at the same place. Each subject ran two laps with a one minute rest in between. The instruction for the first lap was: "try to run the first lap very slowly, just slightly faster than your average walking pace." For the second lap they were instructed to run: "somewhat faster but still not maximally." They were also instructed to keep their chosen velocity, once it had been selected, as constant as possible throughout the lap. HR was registered continuously, however; only the reading from the last 30 s of each interval was used in the calculations. Likewise, the subjects were encouraged to rate their degree of perceived exertion immediately before the finish of each interval, based on the exertion they experienced during the later part of the interval.
Calculations and statistics
Arithmetic means and SE of means were calculated. A number of general reference levels, based either on the HR or on the RPE, were chosen and the subjects corresponding power in watt (cycle test), or velocity in m-[s.sup.-1] (run test), were calculated by fitting a straight regression line to the intensity - HR/RPE data. The chosen reference levels were: HRs of 150 and 170 b-[min.sup.-1] and RPEs of 15 and 17. Thus, the calculated values, subsequently used for statistical analyses, were for the cycle test: [W.sub.150], [W.sub.170], [W.sub.R15],' and [W.sub.R17], corresponding to the power (in W) that the subject performed at a HR of 150 and 170 b-[min.sup.-1] respectively, and at RPEs of 15 and 17. Corresponding values for the run test were: [V.sub.150], [V.sub.170], [V.sub.R15], and [V.sub.R17], i.e. the velocity (in m-[s.sup.-1] at the above mentioned levels. A calculation was also made of each individuals RPE-value at a specific HR level to make further comparisons possible. Specifically, RP[E.sub.150] (cycling) and RP[E.sub.170] (running) were calculated, that is, the subjective rating given at a HR of 150 b-[min.sup.-1] (cycle test) or 170 b-[min.sup.-1] (run test).
A series of one-way analyses of variance (ANOVAs) were used to test whether significant differences were present between the groups (factorial) or within the groups (repeated measures). In addition, a two way ANOVA for repeated measures (Group: Females - Males x Reference values: RP[E.sub.150] - RP[E.sub.170]) was used to detect a possible interaction between group and the activity related reference levels.
The cardiovascular data were previously presented in Table 1. The males were on the average taller and heavier than the females, they also had a higher est. V[O.sub.2max] and est. V[[O.sub.2max].sup.-kg-1] than the females.
In Table 2, the obtained HRs and RPEs from the ergometer cycle test is shown for the females and males.
[TABULAR DATA FOR TABLE 2 OMITTED]
Using the HR:RPE ratio (and the hypothesized relation of 10:1) as a way to compare the correspondence between physiological stress and the subjective perception of that stress, the males show smaller deviations in comparison to the females, especially at the lower work load (HRs). Groupwise, the only significant difference detected was present at the lowest work load for the heart rates ([F.sub.1,46] = 20.15, p [less than]. 001), males exhibiting lower HRs than the females.
The small differences, for females and males respectively, between HR based values ([W.sub.150] and[W.sub.170]) and values based on the subjects RPE ([W.sub.R15] and [W.sub.R17]) can also be seen in the upper half of Table 3 where the calculated fitness values from the cycle ergometer test are displayed. A calculation was also made of each individual's RPE-value at a HR of 150 b-[min.sup.-1] (i.e. RP[E.sub.150[), group means are shown at the upper right hand side of Table 3. The 'deviation' between the expected RPE-value (15) and the obtained value for the females is -0.5, whereas the males exhibit a value of 15.5 (+0.5).
The mean running velocity for the female group was 2.61 and 3.29 m-[s.up.-1] which resulted in HRs of 156 and 177 b-[min.sup.-1] with RPEs of 11.7 and 14.9 respectively.
Velocities for the male group were: 3.20 and 3.99 m-[s.sup.-1], corresponding HRs were 154 and 176 b-[min.sup.-1] with RPEs of 14.0 and 16.8.
The differences observed in the raw-data values between HRs and RPEs for the female group, are reflected in the calculated fitness values presented in the lower half of Table 3. Smaller differences were observed for the males.
[TABULAR DATA FOR TABLE 3 OMITTED]
At the bottom right hand side of Table 3, a calculation has been made of RP[E.sub.170], that is, the RPE-value corresponding to a HR of 170 b-[min.sup.-1] during the outdoor run test. According to previous results, expected RPE-values during running, at a HR of 170 b[min.sup.-1], should correspond to approximately 15 (cf. Borg, van den Burg, Hassmen, Kaijser, & Tanaka, 1987; Ceci & Hassmen 1991; Hassmen 1990). For the males, the mean [RPE.sub.170] was 15.8 whereas the mean for the female group was 13.2. A comparison between [RPE.sub.150] (cycling) and [RPE.sub.170] (running) show that whereas the females' RPE values were significantly different (14.5 vs 13.2; [F.sub.1,23] = 5.86, p [less than] .03), the male values were not (15.5 vs 15.8), see Table 3. The two-way ANOVA confirmed these findings; the main effect of group reached significance ([F.sub.1,46] = 17.26, p[less than].001) whereas the effect for reference values did not ([F.sub.1,46] = 2.77, ns). Furthermore, the interaction between group and reference values was significant ([F.sub.1,46] = 5.78, p[less than].03) thereby confirming the significantly lower ratings made by the females during the running exercise.
The outdoor run test thus revealed distinct differences between the groups, that is; for each HR-level, the female group rated their degree of perceived exertion between two and three RPE-units lower than did the male group.
A major finding in this study was the comparably small differences observed between males and females in regard to HR and RPE during the cycle ergometer test, and the considerably larger differences noted during the outdoor run test.
As for the run test, the female group seem to rate their perceived exertion lower than can be expected from the HRs, and the relations observed during the cycle ergometer test. Also the male group rate their exertion slightly lower during the run test than what would be expected from their HRs, although this latter finding is not new. In a number of previous studies, comparing cycling and running, it has often been observed that while a rating of 15 on the RPE-scale corresponds to a HR of around 150 b-[min.sup.-1] during cycling exercise, the HR may reach approximately 170 b-[min.sup.-1] for the same subjective rating during running exercise (e.g., Borg, van den Burg, Hassmen, Kaijser, & Tanaka, 1987; Ceci & Hassmen 1991; Hassmen 1990). Thus, to observe RPEs that are approximately two units lower than the "corresponding" HRs is quite often encountered when running is the mode of exercise, although the females ratings in the present study are even lower. Was it not for the fact that these gender differences were almost non-existent during the cycle ergometer test, one could suspect that the larger discrepancy between HR values and RPE values for the females, in comparison to the males, were simply due to differences in maximal HRs. Given that women generally obtain higher HRs than males (e.g. Astrand, Cuddy, Saltin, & Stenberg, 1964), a difference might possibly exist between the genders at any given level with women reaching higher HRs at comparable levels of RPE.
There are, however, other elements more likely to explain why there are differences between the genders when cycling and running are compared. A possible factor is of course the difference in body mass and, consequently, in muscle-bulk between the genders. During cycling, local effects such as muscle fatigue and lactate accumulation are known to consistently override central sensation like HR and ventilation, which tend to be more important contributors in determining perceived exertion during running (e.g., Carton & Rhodes, 1985). Since the mean body mass of the female groups was equivalent to about 58 kg per person, in comparison to the male average of 73 kg, this "handicap" of about 15 kg could result in considerably higher ratings during cycling than during running where it is more of an advantage to weigh less. If this explanation is plausible, then it can be inferred that women consistently tend to underrate their exertion more than men; although this tendency is more observable during running than during cycling simply due to the physiological demands of the former activity.
Another viable factor is the environment itself, i.e. laboratory versus field. It has been suggested that women listen more to inner mood cues, in contrast to men who to a greater extent listens to environmental cues (Frazier & Fatis, 1980). If this is correct, then one can deduce that men should change their rating behavior to a greater extent than women when exercise is performed in a less controlled environment such as outdoors as compared to the strict surroundings of the laboratory. If anything, the results of the present study points in the opposite direction in that the female group tend to change their rating behavior more than the male group. The females were supposedly equal to the males in regard to prior athletic experience, at least quantitatively. A closer look at the groups revealed that although the females were as active as the males, their mode of exercise was different. More women than men participated in sports like aerobics, badminton and gymnastics than did men. Generally, the active females were active in some sport mostly performed indoors and in the company of others. The males on the other hand, even though some performed indoor sports, were to a higher degree performing outdoor sports predominantly alone (running, bicycling, race-walking, but also soccer). Thus, experience per se is most likely not the vital issue, experience with either indoor or outdoor sports, and possibly whether the sport is performed in a group or alone, can explain more of the variance observed between females and males.
Within the limitations of the current research design, it is hard to conclude that the observed difference in rating behavior between females and males solely can be attributed to their respective prior experience with indoor and outdoor sports respectively. Future studies should assure that the participating subjects are closely matched not only in regard to prior experience in a general meaning, but also in regard to the specific sport activity performed. Possibly, males and females, even though they perform the same sport, may be different in the way they rate their perceived exertion. The factor or factors responsible for this difference in rating behavior remains to be detected.
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|Publication:||Journal of Sport Behavior|
|Date:||Aug 1, 1996|
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