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Behavioral Medicine Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/vbmd20
Self-Perception of the Ability to Work in the Cold a
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Dr T. M. Nelson PhD , Dr J. W. R. McIntyre MD , Mr I. G. LaBrie BA & Mr A. Csiky BA a
University of Alberta , Edmonton, Canada
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University Hospital , Edmonton
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University of Alberta , USA Published online: 09 Jul 2010.
To cite this article: Dr T. M. Nelson PhD , Dr J. W. R. McIntyre MD , Mr I. G. LaBrie BA & Mr A. Csiky BA (1991) Self-Perception of the Ability to Work in the Cold, Behavioral Medicine, 17:1, 15-23, DOI: 10.1080/08964289.1991.9937548 To link to this article: http://dx.doi.org/10.1080/08964289.1991.9937548
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Self-perception of the Ability to Work in the Cold
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T. M. Nelson, PhD, J. W. R. Mclntyre, MD, I. G. LaBrie, BA, and A. Csiky, BA
Accumulating evidence of beneficial effects from physical exertion must be balanced against increased risk of cardiac arrest during performance. There is evidence that, by using such cues as heart rate, individuals can monitor their level of exertion perceptually. We undertook experiments to discover whether temperature and heart rate interact to affect selfperception when the effective temperature is moved downard from the comfort zone. In the first pilot study, 36 males practiced a new game, SwedeBall, for a period of 20 minutes. Twelve were randomly assigned to play at a temperature of 22°C. another 12 to play at O'C, and the remaining 12 to play at - 7°C. The players showed tendencies toward an overall improvement in self-evaluarions after brief practice, with more favorable responses when the temperatures were lower. In a second experiment on different days, 8 men pedaled a standard bicycle mounted as a wind trainer in a controlled environment chamber where the effective temperature was set at 26"C, Sac, or - 10°C. The first 5-minute ride at each temperature was at a heart rate of 120 beats per minute (bpm), the second at 140 bpm, and a third at 160 bpm. We measured ratings of perceived effort (RPE), thermal impression, discomfort, perceived rate of speed, and projected endurance. The result confirmed that RPE was lowered by temperature when heart rate was constant. The data also showed that the lowered temperatures uniformly produced more favorable selfperceptions on the other four scales. The outcome is related to physiological problems that might arise when temperature depresses heart rate and reduces the experience of effort.
During vigorous exercise, the likelihod of cardiac arrest is increased. This increase has been estimated to be 5 times greater for physically active men and 56 times greater for men who exercise vigorously for less than 20 minutes per week and have been designated sedentary.' Thus, though there is evidence of the beneficial effects of physical activity for general health, such activity should
be undertaken cautiously. The increased cardiac risk appears to stem from the physiological requirement to maintain blood pressure sufficient to support the functioning of vital organs and working muscles while serving the homeostatic need for effective thermoregulation. If the motivational demand happens to exceed the physiological capability, the cumulative effect of vigorous activity will be associated with an increasingly less effective cardiovascular response' and an increased risk of heart failure. The magnitude of increased risk will depend upon environmental and physiological factors such as the ability of the air to accept heat transfer, the functional capacity of the circulatory system, and the individual's
Dr Nelson is a professor of psychology at the University of Alberta (Canada) in Edmonton, Dr Mclntyre is a professor with University Hospital in Edmonton, and Mr LaBrie and Mr Csiky are students at the University of Alberta.
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ABILITY TO WORK IN THE COLD
METHOD
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motivation to continue exercise and his or her perception of physiological welfare. An important step toward understanding of the perception of exertion arose from the research of Borg,'v4 who devised and refined a measure called the Rating of Perceived Effort (RPE). This provides an assessment of how much the individual perceives he or she is exerting himself or herself, rather than the quantity of observed work. We found it interesting that Borg's original scale was coordinated to heart rate so that the index of effort multiplied by 10 would yield the average heart rate of middle-aged Swedish men exercising on a bicycle ergometer. Although the RPE measure is multifactorial, its correlation with heart rate is high-Borg4 states that r = .SO, approximately. The relationship between exercise and RPE appears to be affected by a number of factors operating in ways that make it unlikely that a single local or central physiological factor can account for variations in RPE at different workload^.^ Ambient temperature is one environmental factor of importance."* High temperature conditions are of significance because of the need for heat dissipation, and the effect of low environmental temperature upon RPE is important because sedentary persons occasionally exert themselves greatly in a cold environment. Activities such as shoveling snow or pushing stalled or stuck vehicles are common stresses in cold latitudes.
RESEARCH DESIGN We conducted two studies. The first was a pilot study designed to discover whether RPE and other subjective assessments might reflect temperature in a real-life activity. This possibility was confirmed, leading to a laboratory experiment in which temperature and heart rate were manipulated to vary RPE and related perceptions. Basic to the experiment later reported was the desire to know the extent to which cardiac frequency per se determines self-perception when the effective temperature' is moved downward from the comfort zone.
Pilot Study The pilot study was conducted both out of doors and in a controlled environment chamber (to clarify the effects of lower environmental temperature upon perception of effort). Subjects were required to practice an unfamiliar game at one of three temperatures: 22°C. O"C, and - 7°C. We assessed subjective effort, body discomfort, and fatigue. The subjects also evaluated the game at the end of the experiment to determine how temperature affected their own perception of the activity.
16
Subiects
Thirty-six male volunteers enrolled in an introductory psychology course served as subjects, and each received experimental credit for participating. All reported being in good health and, after being briefed about the task, expressed willingness to learn and to practice a new game.
Mate"& The game selected was SwedeBall (SB), a new ball game developed in Sweden that enjoys considerable popularity. Sports clubs and competitions have been organized, and the game has been endorsed by the Swedish royal family." It is played indoors and outdoors during winter and summer. Its novelty, plus the fact that the game can be played wearing ordinary winter street apparel and in a comparatively small space, made SB well suited to our purpose. SwedeBall is a modification of table tennis in which angles within the table structure increase the variation in ball trajectory. It is normally played by two persons using badminton rackets and a special sponge ball. We used three self-rating scales to evaluate the psychological effects of playing in each of three different ambient temperatures. The first was Borg's4 RPE. This required subjects to rate the effort they expended on a numerical scale ranging from 6 to 20. Accompanying verbal equivalents range from very, very light to very, very heavy. The second was the Physical Sensations Questionnaire, which asked subjects to rate themselves on a Cpoint scale with respect to 18 body distresses that commonly accompany exertion." A third scale was the Feeling Tone Checklist," in which participants rated thernselves on 13 statements, using a ICLpoint scale. Summing the ratings provided a standardized measure of subjective fatigue. The fourth was a nonpersonal questionnaire that requested subjects to describe SB on 10 dimensions. Five of these were positive and 5 negative. Specific terms were active, exciting. pleasant, cornfortable. and friendly versus hectic, frustrating, depressing, rough, and bad. The 5-point rating scale we used ranged from not at all to exceptionally descriptive.
Procedure Twelve of the volunteers were randomly assigned to each of three temperature conditions, namely, 22"C, 0 ° C and -7°C. The higher temperature selected approximates the standard winter indoor temperature in AIberta, and the lower temperatures represent abovenormal outdoor conditions in January. Those in the
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NELSON ET AL
22°C condition practiced inside a university field house under adequate artificial illumination. Those serving in the 0°C and - 7°C temperatures practiced outdoors and used natural light. The outdoor location was a concrete surface cleared of snow and ice and sheltered from both wind and direct sun. AU tests were conducted between the hours of 11 A M and 3 PM. Outside tests were restricted to days on which the air temperature was stable, the air still, and the sky clear. Tests were conducted in the following way. The subjects were assembled in groups of three at an indoor location and were briefed about SB and the place where practice would take place. Next, those subjects who were to practice outdoors were told that they would be exposed to the natural weather for about 45 minutes and that they should dress appropriately. Those praticing indoors were told that they might remove whatever clothing they considered excess before practicing. Upon arrival at the game location, each participant completed the RPE, a Physical Sensations Questionnaire, and a Feeling Tone Checklist. Next, the experimenter demonstrated SB and practiced it with each subject for 3 to 5 minutes. Following this, a practice tourney was held; each player practiced with each of the other two players for a IGminute period. When the three units of practice were completed, the subjects filled out all four questionnaires, were debriefed. and were dismissed.
RESULTS The problem was to determine whether practicing a new game at lower temperatures (0°C and - 7°C) would result in different self-evaluations and game perceptions when compared with playing at a higher temperature (22°C). Previous experience led us to expect most of the 15 sets of ratings to show a weak central tendency. Because of this, the Mann-Whitney U Test was used to test for differences. The criterion for significance was set as p < .05. We found significant differences when we summed and compared measures for the 18 physical symptoms at 0°C and 22°C. Body distress was most noticeable after play in the 22°C condition and least noticeable at 0°C. At -7"C, body discomfort tended to increase compared with that at O"C, reflecting more frequent reports of chill. There was, however, an accompanying decline in drowsy reports. Borg's RPE scale ratings ranged between values of 8 and 19, ie, between ratings equivalent to very light and very, very hard. The overall median rating was 13 (somewhat hard). Once more, the Mann-Whitney test indicated a significant difference, favoring the 0°C condition over that of 22°C. The data also indicated a
Spring 1991
tendency (p < .lo) for effort to be greater at an air temperature of 22°C than at - 7°C. There was no clear indication that temperature played a significant role in determining the extent and direction of pre-post measures of fatigue. The tendency (p < .lo), however, was for fatigue to have the highest value when the air temperature was 22°C. Interestingly, the ratings of subjective fatigue were in a direction contrary to RPE, ie, fatigue was decreased by the play activity, whereas effort was increased. The fatigue reduction was mirrored by ratings made of the game. When, at the end of the play period, subjects rated SwedeBall on 5 positive and 5 negative dimensions commonly used in environmental r e ~ e a r c h , ' ~positive *'~ ratings dominated. The average of ratings made to the terms active, exciting, pleasant, comfortable, and friendly indicated that these positive qualities described the game for the players very well to moderately well. In contrast, the average of ratings t o hectic, fwtrating, depressing, rough, and bad indicate that the negative characteristics fitted slightly to not at all. The game, however, was not rated differently from one ambient temperature to another. This indicated that personal evaluations were not being influenced by changed perception of SB as the temperature was changed. DISCUSSION
The outcome of the pilot study suggests that air temperature lower than those considered to be comfortable9 can lead to more favorable ratings of body state and can reduce the experience of effort. The fact that RPE varied with ambient temperature, being higher in the comfortable climate, suggested that heart rate may have been higher for those who practiced in the 22°C condition."" This conjecture is consistent with results obtained by LeBlanc,16who reported that, when the face is exposed to temperatures ranging between 40°C and -1O"C, heart rate declines as the temperature of the forehead declines. Riggs et a18 confirmed the relationship, using wind to reduce the effective temperature. In addition, slowing heart rate by lowering face temperature is an established technique used in medical resear~h.".'~ Experimental Study
The pilot investigation suggests that self-assessments made after brief physical exertion were influenced by the ambient temperature, ie, RPE and related perceptions were higher in comfortable temperature than they were in low ambient temperatures. Assuming, as do others," that there is a close relationship between the perception of effort and heart rate, we may suppose that the average
17
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ABILITY TO WORK IN THE COLD
heart rate was highest for the group that practiced SB in the 22°C condition. Assuming, further, that the average subjects in each group practiced SB equally hard, we might conclude that heart rate became highest in the 22°C condition because of differences in ambient temperature, the full face being completely exposed to the air in every condition. In this subsequent investigation, we required subjects to pedal a standard bicycle mounted as a wind trainer in a controlled environment chamber where ambient temperature was held steady at three different levels. Work performance was defined by heart rate, which also was held at constant levels throughout the periods of work. The dependent variables we studied were perceived effort,’ subjective comfort, thermal sensation, pace or rate of work, and predicted work endurance. All dependent variables were rated using an RPE format. If the interpretation made of pilot data was correct, all five subjective assessments would reflect heart rate. We included perception of temperature because significant body heat develops during vigorous exercise. Thermal perception aside, the prediction that perception would vary with heart rate is consistent with what is already known. If these perceptions should reflect an interaction between heart rate and ambient temperature, however, this outcome would imply possible difficulty for individuals using self-perception in safely regulating activity. The implication of such an effect would depend, of course, upon the direction of the relationship and the extent of the disparity between heart rate and the self-perceptions. METHOD Subjects
Eight nonobese university students served as subjects and, for their participation, received credit toward satisfaction of their research requirement. No participant was engaged in athletic training or competitive athletics. None reported disease symptoms of any type or any immediate or long-term health problem as assessed by a standard questionnaire provided by the faculty of recreation and leisure studies that was used to determine fitness to participate in experiments requiring vigorous physical exercise. Materials and Equipment
The investigation was undertaken in a universityoperated climatic chamber that measured 3.81 m x 3.23 m, with a ceiling height of 2.35 m. This unit is soundattenuated and allows precise setting and constant automatic monitoring of ambient temperature and humidity.
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Air velocities range from 0.086m/second to 0.233 d s e c ond. The air is constantly fresh, and the ambient temperature gradient from floor to ceiling rarely exceeds 1°C. The subjects exercised on a standard road bicycle mounted as a wind trainer. A standard electronic device (Exersensory) measured heart rate while the participants pedaled, and output was displayed in digital form at a location visible to the experimenter. The experimenter signaled the rider to increase or decrease rate of work as required. Riders did not receive any external indication of what their heart rates were, but the Exersensory incorporated an auditory alarm that signaled when heart rate deviated by 3 bpm or more upward or downward from the set point. We measured five subjective states. These were (1) awareness of effort, (2) perceived rate of work in relation to maximum possible, (3) estimation of the length of time performance could be sustained at the given heart rate, (4) felt level of discomfort, and ( 5 ) experienced ambient temperature. Effort was measured using the RPE. The four remaining subjective states were measured using an identical format, ie, participants registered perceptions by selecting a number from a series from 6 to 20. The beginning and ending points of these four scales and selected points between also were given verbal labels. More specifically, in the case of rate of work, descriptions started at no motion (6) and terminated at maximum speed (20). Accompanying directions asked the subjects to “give your personal estimate of how hard you felt you were pedaling in relation to what you could do going ‘flat out.’ ” The estimate of endurance started with inde3nitely at point 6, moved to I hour at point 7, and declined to I minute at point 19 and less than 30 seconds at scale point 20. The subject was to estimate “how much longer do you think you would be able to keep up the work you were doing.” The discomfort scale was bounded by totally comfortable and unbearable. Instructions asked that the subjects rate “overall body state at the end of exercise.” The thermal scale started with very cold and concluded with very hot. Accompanying instruction asked the subject to remember that he was expected “to represent your personal perception of the thermal environment.” Procedure Experimental sessions took place in temperatures of 26”C, 8°C. or - 10°C. with relative humidity futed at 40%. Sessions were always at a single ambient temperature, and each session was separated by at least a full day. During each session, the subject pedaled the wind trainer at three rates. Rate A was that sufficient to
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maintain heart rate at 120 bpm, rate B at the rate measured to achieve 140 bpm, and C at that to maintain 160 bpm. The subject always started at a rate of 120 bpm, followed by 140 bpm, then 160 bpm. Duration of exercise was 5 minutes. While working, the rider wore shoes, socks, and shorts. The upper trunk was bare except for the heart rate electrode taped to the chest. Self-assessments were filled out immediately upon completion of each exercise regimen.
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RESULTS The data in Table 1 summarize ratings made on the five psychological scales by the 8 subjects while working in room temperatures of 26°C 8 ° C or - 10°C when rate of work was sufficient to raise cardiac frequency to 120 bpm, 140 bpm, or 160 bpm. Notice that in all but one of the 24 cases, feelings of exertion also increased when heart rate was increased at a particular temperature. This was what would be expected using Borg's scale. Of greater interest is that RPE ratings changed with temperatures when heart rate was held constant at 120 bpm, 140 bpm, or 160 bpm. The data in Table 1 indicate that perceived effort decreased significantly as temperature declined. The result was particularly reliable for the condition of greatest physical exertion (160 bpm), at which all subjects showed the same effect. lnterpreting this in the language of the scale indicates that effort diminished as temperature shifted from 26°C to - 10°C from something near very hard to a state situated between hard and somewhat hard. Data averaged over subjects, depicted in Figure 1, shows a progressive increase in perceived effort for each of the heart rates as the temperature rose. The closest correspondence between RPE ratings and heart rate was at 26°C. ie, the only thermal environment in the range of comfortable indoor temperatures as defined by engineering standard^.^ Note that when the average RPE ratings made at 26°C are multiplied by 10, the product approximates heart rate. Considering the differences in the age of our subjects and the original middle-aged standardizing group, the outcome for the 26°C condition was consistent with Borg's fir~dings.'~ Ratings on the Thermal Impression Scale indicated that average perceptions of the three thermal environments bore an ordinal relation to ambient temperature changes for each of the three conditions of physical work (heart rates), as expected. It also appeared that thermal impressions were reliably affected by workload. At all three temperatures, with one minor exception, the environment was rated warmest when heart rate was highest. The order of ranks was highly reliable at all three temper-
Spring 1991
atures. It appeared that exercise affected the impression of the warmth of the physical surroundings. In addition, thermal impression was highly correlated with changes in RPE, confirming that workload had a great effect upon the acceptance of the t h e d environment. In ordinary language, the thermal environment changed from being cool to being neutral (comfortable) when RPE increased from moderate to heuvy levels. Discomfort had a less simple relation to heart rate. Figure 1 shows that as heart rate increased, discomfort ratings increased so long as temperatures were 8°C or 26°C. However, when temperature dropped to - 10°C. the order of ratings of discomfort were altered, the highest being when the heart rate was slowest, presumably because the lightly clad bicycle riders became chilled (rated the thermal environment as cool). Given present perspective, the most important outcome was the sizable and reliable decrease in discomfort (increase in comfort) that occurred when temperature was reduced in the 160 bpm condition. Expressed in terms of the verbal scale, the average discomfort experienced doing the hardest work moved from being definitely uncomforlable to a position between slight and minimal discomfort as temperature decreased to - 10°C. It is interesting to note that the greatest discomfort in absolute terms was reported by Subjects 4 and 6 when their heart rates were 160 bpm and the air temperature was 26°C. Pace judgments were consistent over heart rates at all temperatures. At each temperature, the participants had to pedal most rapidly to maintain their heart rate at 160 bpm. This physical fact was present in subject ratings, which argues for the validity of the scale, but a new fact emerged when subjects' impressions of their nearness to maximum speed were compared across temperature conditions at each heart rate. The subjects were prone to judge their rate of pedaling to be close to their maximum capacity at high temperatures for the 160 bpm heart rate (see Figure I). The most optimistic self-perceptions were associated with the lowest temperature and 120 bpm. Comparing across temperatures shows that all 8 subjects rated themselves as farthest from maximal pedaling speed at the lowest temperature, ie, they all felt that they could increase their speed most at - 10°C. It was surprising and somewhat disturbing to note that, in spite of the considerable cardiac stress subjects were being subjected to at a heart rate of 160 bpm, all in the - 10°C condition judged that they were pedaling at less than 75% of maximum; and Subjects 2 and 7 actually considered themselves to be performing at or less than 50% of maximum. In sum, those working in a low temperature felt that they had considerable reserve to draw upon if they should de-
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ABILITY TO WORK IN THE COLD
FIGURE 1 Graphic Representation of the Relationship Between Temperature, Heart Rate, and Averages of Five Types of Self-Assessments Given by 8 Subjects.
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2o
1
I
140
160
r
I 140
Heart Rate (BPM)
Heart Rate (BPM) 20
-
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18
-
18 -
16
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TABLE 1 Ratings of Perceived Effort, Thermal Sensation, Discomfort, Pace, and Endurance Given by 8 Subjects AfIer Performing 5 Minutes of Cycling on a Wind Trainer in One of Three Temperatures While Maintaining Head Rate Constant at 120,140, or 160 Beats per Minute
Subject
Effort 120 140 160
Thermal 120 140 160
26°C 1 2 3 4
12 10 12 11
5
11
15 17 15 17 15 17 12 15
17 17 17 18 18 17 I5 17
14
6 7 8 8°C 1 2 3 4 5 6 7 8 - 10°C 1 2 3 4 5 6 7 8
18 17 16 18 15
12 12 12
14 15 14 15 13 13 14 14
12 10 12 8 11 11 11 12
13 13 13 16 12 14 13 14
17 15 15 17 14 17 15 19
9 9 9 7 9
12 12
II
10 12 12
I5 15 12 15 13 12 13 14
9 10
10
12 11
15 16 18
11 15
13 9 12 10 14 11 11 7 8 7 11 11 7
Discomfort 120 140 160
Pace 120 140 160
18 18 18 19 19 19 18 19
10 7 11 12 12 14 9 9
12 10 13 16 16 15 11 13
14 15
10 9 13 10
16 17 15 18 15 16 13 16
18 18 17 19 19 15 16 18
9 6 9 11 7 9 8 8
10
13 14 13 15 14 13 14 13
11 10 10 11 12
12 12 7 10 9 11 13 8
13 13 8 15
10 8 12 15 13 8 8 13
11 9 11 13 11 9 9 12
12 10 10 14 10 12 13
11
14 16 10
1
cide to increase their rate of performance, notwithstanding their high heart rate, of which, of course, they lacked objective knowledge. Projected endurance judgments reinforced the conclusion that low temperature distorted judgments of personal capability. On the one hand, we found a benign relationship between projected endurance and heart rate when temperature was held constant. That is, projected endurance declined as heart rate increased in each thermal environment. This was also demonstrated by the fact that the median rating for all heart rates was 6 for 120 bpm, but 13 for 160 bpm. However, the bynow-familiar pattern again unfolded when we studied the relationship of projected endurance to temperature. Estimates of how much longer the rider could last in-
Spring 1991
11 11 13
11 14 11
10
I5 17 16 17 15 16
11
Endurance 120 140 160
15 17
8 13 13 8 6 9 6 6
10 14 16 14 7 II 12 7
13 16 18 17 10 13 14 10
10 12
12 12 13 18 16 13 13 14
16 14 15 17 17 16 16 16
6 11 12 10 6 7 6 6
10 13 15 13 7 10 12 7
13 I5 17 17 8 13 13
9 8 9 7 10 13 9 9
12 I1 11 10 13 14 12 12
15 12 14 I5 15 15 13 15
6 11
6 13 13 12 9 9 6 6
9 14
11 11
9 11
10
15 12
15 16 16 14 13 14
17 17 16 19 18 18
10
6 6 6 6 6
10
15 15 12 7 7 7 I
creased as the temperature declined at all three workloads (heart rates; see Figure 1). In the most demanding condition, the estimate doubled when temperature was reduced from 26°C to - 10°C. The word equivalents to the scale values are informative. When the scale values given in Table 1 are translated into words for an environment of - 1O"C, they disclose that half of the subjects whose heart rate was 160 bpm believed themselves to be capable of continuing for 50 minutes or more and that Subject 5 regarded the stress so minimal that he might continue indefinitely. In contrast, the identical subjects working in the temperature of 26°C with heart rate 160 bpm judged themselves as capable of continuing for a much shorter period, that is, continuing only 5 to 45 minutes longer.
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DISCUSSION
The average self-assessment made immediately after vigorous exercise in temperatures ranging between 26°C and - 1O"C, indicates that (1) reducing the temperature diminished the awareness of effort from a condition near very hard to one between hard and somewhat hard; (2) assessment of the thermal environment moved from cool to comfortable as heart rate was increased in the - 10°C condition; (3) the level of experienced discomfort decreased from uncomfortable to a position between slight and minimal discomfort at - 10°C; (4) subjects whose heart rate was 160 bpm judged that they were performing at less than 60% of maximum capacity at - 10°C v judging that they were over 80% maximum at 26°C; and ( 5 ) half of the subjects working in the - 10°C environment believed that they could maintain a pace of work producing 160 bpm for 50 minutes or more, whereas none of these same persons working at 26°C held this opinion. It is clear from their ratings that participants felt more confident of their abilities and were more Comfortable in the cool environment. A conclusion that these experiments demonstrate that the accuracy of perceptions of work done or work that could be done are significantly influenced by environmental temperature, however, would rest upon an assumption that the same amount of work was being done at each of the selected pulse rate and temperature combinations. Because measurements of physical or physiological work were not made, such an assumption may be unjustified, but there is some evidence suggesting that this might be true. One of the factors affecting the relationship of RPE and heart rate is temperature. Pandolf and colleagues6 increased heat stress and found that heart rate and RPE increased at disproportionate rates. Bergh19 studied both elevated and depressed body temperature in relation to several types of work and found systematic changes in RPE and heart rate. Bergh attributed these to several types of biological change that occur at different rates, depending upon the way environmental contact is made. Thus, the evidence is reasonably consistent that persons are unequally aware of their internal state and work potential in comfortable and cool environments. If this is to be extrapolated to an individual exercising in the cold, additional factors must be considered. One is that the body temperature of a person clad to maintain a feeling of comfort in the cold is likely to increase when physical work is in progress. Another is the effect of a cold environment on exposed skin and mucous membranes. There is a progressive reduction in heart rate when
22
the surface of the face, particularly of the forehead, is exposed to increasingly lower temperatures,16and heart rate influences the perception of exertion, as Borg" pointed out. The matter is not simple, however, at either the physiological or the psychological level. Riggs et al" found that the relationship of ambient temperature and heart rate progressively changes within one period of exertion in ways apparently determined by ambient temperature. Other researchMhas demonstrated that heart rate, RPE, and thermal sensation all declined as a result of acclimatization to heat. As Pandolf'l suggested, heart rate per se may not be the major determiner of perceived exertion during exercise. In addition to attempting to identify new mediators for RPE, consideration might be given to an alternative definition of the dependent variable. The awareness of psychological factors such as type of physical a~tivity,~ time experience, thermal awareness, rate of performance, and perceived locus of muscular discomfort are among those items deserving more attention. A solution to the problem of perception of effort may require an approach deviant from that in use since 1%2. One alternative is to pursue a hierarchical model to explain perception of effort, an approach effectively used for muscular fatigueU and sedentary work fatigue.*' Another would be similar to that taken by Rohles and Millikenu for comfort perception. Their comfort scale is in semantic differential form, derived from a factor analytic procedure and scored using ratings and dimensional loadings. CONCLUSION
Physical competition encourages players to drive their physiological capabilities to their limit, and obsessive persons may feel a task once started must be completed. Body signals are assessed to determine those limits. The results of our study suggested that the assessment of physiological resources varied depending on both the work itself and the thermal environment in which exertion has taken place. Among the body signals used, heart rate may be unreliable. The results indicated several instances wherein self-perceptions were clearly wrong and, if acted upon, would stress the cardiac system significantly. This experiment was conducted with healthy young subjects. It is interesting to consider the implication of the results for persons with impaired cardiovascular function who work or exercise in a cold environment. The potentially misleading perception of well-being could lead to overwork or overexercise. An oxygen debt associated with cooling of environment and resulting re-
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distribution of blood flow and temporary metabolic acidosis could also lead to sudden cardiac dysfunction. The misreading of body signals is thought to play a role in the causation of sudden cardiac death.=*%Future studies will attempt t o clarify the relationship between work done, perception of work done, perception of work potential, body ambient temperature, and environmental temperature. INDEX TERMS cold, exedoa, fatigue, beut rate, pemptioa, temperature
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RM. eds. Perspectives in Erercise Science and Sports Medicine. vol I. Indianapolis. IN: Benchmark Press; 1988. Raven PB. Stevens HJ. Cardiovascular function and prolonged exercise. In: Lamb OR, Murray RM, eds. Perspectives in Exercise Science and Sports Medicine. vol3. Indianapolis, IN: Benchmark Press; 1988. Borg G. Physical Performance and Perceived Exertion. Lund, Sweden: Gleenys; 1%2. Borg G. Perceived exertion as an indicator of somatic stress. Scand J Rehab Med. 1970;2:92-98. Reishman EA, Gebhardt DL. Hogan JC. In: Borg G, Ottoson D. eds. The Perception of Exertion in Physical Work. Houndsmills, NH: The Macmillan Press; 1986. Pandolf KB, Caferelli E, Noble B, Metz KF. Percep Mot Skillr. 1972;35;975-985. Bergh U. Exertion during exercise at different body temperatures. In: Borg G, Ottoson D. eds. Perception of Exertion in Physical Work. Houndsmills, NH: The Macmillan Press; 1986. Riggs CE. Johnson DJ. Konopka BJ. Kilgour RW. Exercise heart rate response to facial cooling. Eur J Appl Physiol. 1981;47: 323-330. ASHRAE Handbook of Fundamentalr. New York: American Society of Heating, Refrigeration, and Air Conditioning Engineers; 1977. Letter from C. Nordstrdm. Hoventendent, to S. Wideman of January 29. 1985. Nelson TM. The Development of Fatigue Under Various Conditions of Comfort and Work Demand. Edmonton, Alberta: Worker's Health Safety and Compensation; 1985. Pearson RG, Byars GE. The development and validation of a checklist for measuring subjective fatigue. Report 56-1 IS. School of Aviation Medicine: USAF, 1957. Kaplan R. Kaplan S. The Experience of Nature. Cambridge. England: Cambridge University Press; 1989. Gifford R. Environmental Psychology. Newton, MA: Allyn and Bacon, Inc; 1987. Borg G. Psychophysical studies of effort and exertion. In: Borg G, Ottoson D. eds. Perception of Exertion in Physical Work; Houndsmills, NH: The Macmillan Press; 1986. LeBlanc J. Man in the Cold. Springfield, IL: Charles C. Thomas; 1975. Khurana RK, Watabiki S , Hebel JR. Tor0 R. Nelson E. Cold face
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test in the assessment of trigeminal brainstem-vagal function in humans. Ann Neurol. 1980,7:144-149. 18. Anderson NB. Lane JD. Muranaka M, Williams RB, Houseworth SJ. Racial differences in blood pressure and forearm vascular responses to the cold face stimulus. Psychosom Med. 1988; 5057-63. 19. Bergh U. Exertion during exercise at different body temperatures. In: Borg G , Ottoson D, eds. Perception of Exerrion in Physical Work. Houndsmills. NH: The M a c h press; 1986. 20. Pandolf KB, Burse RL, Goldman RF. Role of physical fitness in heat acclimatization, decay and reinductor. Ergonomics. 1977; #):39!9-408. 21. Pandolf KB. Psychological and physiological factors influencing perceived exertion. In: Borg G, ed. Physical Work and Effort. Oqford: Pergamon Press; 1977. 22. Kinsman RA. Weiser PC. Subjective symptomatology during work and fatigue. In: Simonson E. Weiser PC, eds. Physiological Correlates of Work and Fatigue. Springfield, IL: Charles C. Thomas; 1976. 23. Nelson TM. Personal perceptions of fatigue. In: Chapman AJ. Wade FM, Foote H, eds. Road w e t y and Practice. Eastbourne. Sussex: Praeger; 1981. 24. Rohles FH. Milliken GA. A scaling procedure for environmental research. Proceedings of the Annual Meetings of the Human Factors Society. Rochester, NY: Human Factors Society; 1981. 25. Cohn PF. Editorial. Silent myocardial ischemia in patients with a defective anginal warning system. A m J Cardiol. 1980;45:697702. 26. Droste C. Roskamm H. Experimental pain measurement in patients with asymptomatic myocardial ischemia. J A m Coll Cardiol. 1983; l(3):WO-5.
NM CONSENSUS PANEL REPORTS National Institutes of Health consensus development statements on Treatment of Early-Stage Breast Cancer and on Intravenous Immunoglobulin: Prevention and Treatment of Disease are available from the NIH Office of Medical Application of Research (OMAR), Building 1, Room 260, 9OOO Rockville Pike, Bethesda, MD u)892 (301) 4S1143. The conference on breast cancer was held in May 1990, that on intravenous immunoglobulin in June of the same year. At NIH, consensus conferences bring together researchers, practicing physicians, representatives of public interest groups, consumers, and others to cany out scientific assessments of drugs, devices, and procedures in an effort to evaluate their safety and effectiveness.
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Behavioral Medicine Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/vbmd20
Self-Perception of the Ability to Work in the Cold a
b
c
Dr T. M. Nelson PhD , Dr J. W. R. McIntyre MD , Mr I. G. LaBrie BA & Mr A. Csiky BA a
University of Alberta , Edmonton, Canada
b
University Hospital , Edmonton
c
c
University of Alberta , USA Published online: 09 Jul 2010.
To cite this article: Dr T. M. Nelson PhD , Dr J. W. R. McIntyre MD , Mr I. G. LaBrie BA & Mr A. Csiky BA (1991) Self-Perception of the Ability to Work in the Cold, Behavioral Medicine, 17:1, 15-23, DOI: 10.1080/08964289.1991.9937548 To link to this article: http://dx.doi.org/10.1080/08964289.1991.9937548
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Self-perception of the Ability to Work in the Cold
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T. M. Nelson, PhD, J. W. R. Mclntyre, MD, I. G. LaBrie, BA, and A. Csiky, BA
Accumulating evidence of beneficial effects from physical exertion must be balanced against increased risk of cardiac arrest during performance. There is evidence that, by using such cues as heart rate, individuals can monitor their level of exertion perceptually. We undertook experiments to discover whether temperature and heart rate interact to affect selfperception when the effective temperature is moved downard from the comfort zone. In the first pilot study, 36 males practiced a new game, SwedeBall, for a period of 20 minutes. Twelve were randomly assigned to play at a temperature of 22°C. another 12 to play at O'C, and the remaining 12 to play at - 7°C. The players showed tendencies toward an overall improvement in self-evaluarions after brief practice, with more favorable responses when the temperatures were lower. In a second experiment on different days, 8 men pedaled a standard bicycle mounted as a wind trainer in a controlled environment chamber where the effective temperature was set at 26"C, Sac, or - 10°C. The first 5-minute ride at each temperature was at a heart rate of 120 beats per minute (bpm), the second at 140 bpm, and a third at 160 bpm. We measured ratings of perceived effort (RPE), thermal impression, discomfort, perceived rate of speed, and projected endurance. The result confirmed that RPE was lowered by temperature when heart rate was constant. The data also showed that the lowered temperatures uniformly produced more favorable selfperceptions on the other four scales. The outcome is related to physiological problems that might arise when temperature depresses heart rate and reduces the experience of effort.
During vigorous exercise, the likelihod of cardiac arrest is increased. This increase has been estimated to be 5 times greater for physically active men and 56 times greater for men who exercise vigorously for less than 20 minutes per week and have been designated sedentary.' Thus, though there is evidence of the beneficial effects of physical activity for general health, such activity should
be undertaken cautiously. The increased cardiac risk appears to stem from the physiological requirement to maintain blood pressure sufficient to support the functioning of vital organs and working muscles while serving the homeostatic need for effective thermoregulation. If the motivational demand happens to exceed the physiological capability, the cumulative effect of vigorous activity will be associated with an increasingly less effective cardiovascular response' and an increased risk of heart failure. The magnitude of increased risk will depend upon environmental and physiological factors such as the ability of the air to accept heat transfer, the functional capacity of the circulatory system, and the individual's
Dr Nelson is a professor of psychology at the University of Alberta (Canada) in Edmonton, Dr Mclntyre is a professor with University Hospital in Edmonton, and Mr LaBrie and Mr Csiky are students at the University of Alberta.
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METHOD
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motivation to continue exercise and his or her perception of physiological welfare. An important step toward understanding of the perception of exertion arose from the research of Borg,'v4 who devised and refined a measure called the Rating of Perceived Effort (RPE). This provides an assessment of how much the individual perceives he or she is exerting himself or herself, rather than the quantity of observed work. We found it interesting that Borg's original scale was coordinated to heart rate so that the index of effort multiplied by 10 would yield the average heart rate of middle-aged Swedish men exercising on a bicycle ergometer. Although the RPE measure is multifactorial, its correlation with heart rate is high-Borg4 states that r = .SO, approximately. The relationship between exercise and RPE appears to be affected by a number of factors operating in ways that make it unlikely that a single local or central physiological factor can account for variations in RPE at different workload^.^ Ambient temperature is one environmental factor of importance."* High temperature conditions are of significance because of the need for heat dissipation, and the effect of low environmental temperature upon RPE is important because sedentary persons occasionally exert themselves greatly in a cold environment. Activities such as shoveling snow or pushing stalled or stuck vehicles are common stresses in cold latitudes.
RESEARCH DESIGN We conducted two studies. The first was a pilot study designed to discover whether RPE and other subjective assessments might reflect temperature in a real-life activity. This possibility was confirmed, leading to a laboratory experiment in which temperature and heart rate were manipulated to vary RPE and related perceptions. Basic to the experiment later reported was the desire to know the extent to which cardiac frequency per se determines self-perception when the effective temperature' is moved downward from the comfort zone.
Pilot Study The pilot study was conducted both out of doors and in a controlled environment chamber (to clarify the effects of lower environmental temperature upon perception of effort). Subjects were required to practice an unfamiliar game at one of three temperatures: 22°C. O"C, and - 7°C. We assessed subjective effort, body discomfort, and fatigue. The subjects also evaluated the game at the end of the experiment to determine how temperature affected their own perception of the activity.
16
Subiects
Thirty-six male volunteers enrolled in an introductory psychology course served as subjects, and each received experimental credit for participating. All reported being in good health and, after being briefed about the task, expressed willingness to learn and to practice a new game.
Mate"& The game selected was SwedeBall (SB), a new ball game developed in Sweden that enjoys considerable popularity. Sports clubs and competitions have been organized, and the game has been endorsed by the Swedish royal family." It is played indoors and outdoors during winter and summer. Its novelty, plus the fact that the game can be played wearing ordinary winter street apparel and in a comparatively small space, made SB well suited to our purpose. SwedeBall is a modification of table tennis in which angles within the table structure increase the variation in ball trajectory. It is normally played by two persons using badminton rackets and a special sponge ball. We used three self-rating scales to evaluate the psychological effects of playing in each of three different ambient temperatures. The first was Borg's4 RPE. This required subjects to rate the effort they expended on a numerical scale ranging from 6 to 20. Accompanying verbal equivalents range from very, very light to very, very heavy. The second was the Physical Sensations Questionnaire, which asked subjects to rate themselves on a Cpoint scale with respect to 18 body distresses that commonly accompany exertion." A third scale was the Feeling Tone Checklist," in which participants rated thernselves on 13 statements, using a ICLpoint scale. Summing the ratings provided a standardized measure of subjective fatigue. The fourth was a nonpersonal questionnaire that requested subjects to describe SB on 10 dimensions. Five of these were positive and 5 negative. Specific terms were active, exciting. pleasant, cornfortable. and friendly versus hectic, frustrating, depressing, rough, and bad. The 5-point rating scale we used ranged from not at all to exceptionally descriptive.
Procedure Twelve of the volunteers were randomly assigned to each of three temperature conditions, namely, 22"C, 0 ° C and -7°C. The higher temperature selected approximates the standard winter indoor temperature in AIberta, and the lower temperatures represent abovenormal outdoor conditions in January. Those in the
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22°C condition practiced inside a university field house under adequate artificial illumination. Those serving in the 0°C and - 7°C temperatures practiced outdoors and used natural light. The outdoor location was a concrete surface cleared of snow and ice and sheltered from both wind and direct sun. AU tests were conducted between the hours of 11 A M and 3 PM. Outside tests were restricted to days on which the air temperature was stable, the air still, and the sky clear. Tests were conducted in the following way. The subjects were assembled in groups of three at an indoor location and were briefed about SB and the place where practice would take place. Next, those subjects who were to practice outdoors were told that they would be exposed to the natural weather for about 45 minutes and that they should dress appropriately. Those praticing indoors were told that they might remove whatever clothing they considered excess before practicing. Upon arrival at the game location, each participant completed the RPE, a Physical Sensations Questionnaire, and a Feeling Tone Checklist. Next, the experimenter demonstrated SB and practiced it with each subject for 3 to 5 minutes. Following this, a practice tourney was held; each player practiced with each of the other two players for a IGminute period. When the three units of practice were completed, the subjects filled out all four questionnaires, were debriefed. and were dismissed.
RESULTS The problem was to determine whether practicing a new game at lower temperatures (0°C and - 7°C) would result in different self-evaluations and game perceptions when compared with playing at a higher temperature (22°C). Previous experience led us to expect most of the 15 sets of ratings to show a weak central tendency. Because of this, the Mann-Whitney U Test was used to test for differences. The criterion for significance was set as p < .05. We found significant differences when we summed and compared measures for the 18 physical symptoms at 0°C and 22°C. Body distress was most noticeable after play in the 22°C condition and least noticeable at 0°C. At -7"C, body discomfort tended to increase compared with that at O"C, reflecting more frequent reports of chill. There was, however, an accompanying decline in drowsy reports. Borg's RPE scale ratings ranged between values of 8 and 19, ie, between ratings equivalent to very light and very, very hard. The overall median rating was 13 (somewhat hard). Once more, the Mann-Whitney test indicated a significant difference, favoring the 0°C condition over that of 22°C. The data also indicated a
Spring 1991
tendency (p < .lo) for effort to be greater at an air temperature of 22°C than at - 7°C. There was no clear indication that temperature played a significant role in determining the extent and direction of pre-post measures of fatigue. The tendency (p < .lo), however, was for fatigue to have the highest value when the air temperature was 22°C. Interestingly, the ratings of subjective fatigue were in a direction contrary to RPE, ie, fatigue was decreased by the play activity, whereas effort was increased. The fatigue reduction was mirrored by ratings made of the game. When, at the end of the play period, subjects rated SwedeBall on 5 positive and 5 negative dimensions commonly used in environmental r e ~ e a r c h , ' ~positive *'~ ratings dominated. The average of ratings made to the terms active, exciting, pleasant, comfortable, and friendly indicated that these positive qualities described the game for the players very well to moderately well. In contrast, the average of ratings t o hectic, fwtrating, depressing, rough, and bad indicate that the negative characteristics fitted slightly to not at all. The game, however, was not rated differently from one ambient temperature to another. This indicated that personal evaluations were not being influenced by changed perception of SB as the temperature was changed. DISCUSSION
The outcome of the pilot study suggests that air temperature lower than those considered to be comfortable9 can lead to more favorable ratings of body state and can reduce the experience of effort. The fact that RPE varied with ambient temperature, being higher in the comfortable climate, suggested that heart rate may have been higher for those who practiced in the 22°C condition."" This conjecture is consistent with results obtained by LeBlanc,16who reported that, when the face is exposed to temperatures ranging between 40°C and -1O"C, heart rate declines as the temperature of the forehead declines. Riggs et a18 confirmed the relationship, using wind to reduce the effective temperature. In addition, slowing heart rate by lowering face temperature is an established technique used in medical resear~h.".'~ Experimental Study
The pilot investigation suggests that self-assessments made after brief physical exertion were influenced by the ambient temperature, ie, RPE and related perceptions were higher in comfortable temperature than they were in low ambient temperatures. Assuming, as do others," that there is a close relationship between the perception of effort and heart rate, we may suppose that the average
17
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heart rate was highest for the group that practiced SB in the 22°C condition. Assuming, further, that the average subjects in each group practiced SB equally hard, we might conclude that heart rate became highest in the 22°C condition because of differences in ambient temperature, the full face being completely exposed to the air in every condition. In this subsequent investigation, we required subjects to pedal a standard bicycle mounted as a wind trainer in a controlled environment chamber where ambient temperature was held steady at three different levels. Work performance was defined by heart rate, which also was held at constant levels throughout the periods of work. The dependent variables we studied were perceived effort,’ subjective comfort, thermal sensation, pace or rate of work, and predicted work endurance. All dependent variables were rated using an RPE format. If the interpretation made of pilot data was correct, all five subjective assessments would reflect heart rate. We included perception of temperature because significant body heat develops during vigorous exercise. Thermal perception aside, the prediction that perception would vary with heart rate is consistent with what is already known. If these perceptions should reflect an interaction between heart rate and ambient temperature, however, this outcome would imply possible difficulty for individuals using self-perception in safely regulating activity. The implication of such an effect would depend, of course, upon the direction of the relationship and the extent of the disparity between heart rate and the self-perceptions. METHOD Subjects
Eight nonobese university students served as subjects and, for their participation, received credit toward satisfaction of their research requirement. No participant was engaged in athletic training or competitive athletics. None reported disease symptoms of any type or any immediate or long-term health problem as assessed by a standard questionnaire provided by the faculty of recreation and leisure studies that was used to determine fitness to participate in experiments requiring vigorous physical exercise. Materials and Equipment
The investigation was undertaken in a universityoperated climatic chamber that measured 3.81 m x 3.23 m, with a ceiling height of 2.35 m. This unit is soundattenuated and allows precise setting and constant automatic monitoring of ambient temperature and humidity.
18
Air velocities range from 0.086m/second to 0.233 d s e c ond. The air is constantly fresh, and the ambient temperature gradient from floor to ceiling rarely exceeds 1°C. The subjects exercised on a standard road bicycle mounted as a wind trainer. A standard electronic device (Exersensory) measured heart rate while the participants pedaled, and output was displayed in digital form at a location visible to the experimenter. The experimenter signaled the rider to increase or decrease rate of work as required. Riders did not receive any external indication of what their heart rates were, but the Exersensory incorporated an auditory alarm that signaled when heart rate deviated by 3 bpm or more upward or downward from the set point. We measured five subjective states. These were (1) awareness of effort, (2) perceived rate of work in relation to maximum possible, (3) estimation of the length of time performance could be sustained at the given heart rate, (4) felt level of discomfort, and ( 5 ) experienced ambient temperature. Effort was measured using the RPE. The four remaining subjective states were measured using an identical format, ie, participants registered perceptions by selecting a number from a series from 6 to 20. The beginning and ending points of these four scales and selected points between also were given verbal labels. More specifically, in the case of rate of work, descriptions started at no motion (6) and terminated at maximum speed (20). Accompanying directions asked the subjects to “give your personal estimate of how hard you felt you were pedaling in relation to what you could do going ‘flat out.’ ” The estimate of endurance started with inde3nitely at point 6, moved to I hour at point 7, and declined to I minute at point 19 and less than 30 seconds at scale point 20. The subject was to estimate “how much longer do you think you would be able to keep up the work you were doing.” The discomfort scale was bounded by totally comfortable and unbearable. Instructions asked that the subjects rate “overall body state at the end of exercise.” The thermal scale started with very cold and concluded with very hot. Accompanying instruction asked the subject to remember that he was expected “to represent your personal perception of the thermal environment.” Procedure Experimental sessions took place in temperatures of 26”C, 8°C. or - 10°C. with relative humidity futed at 40%. Sessions were always at a single ambient temperature, and each session was separated by at least a full day. During each session, the subject pedaled the wind trainer at three rates. Rate A was that sufficient to
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maintain heart rate at 120 bpm, rate B at the rate measured to achieve 140 bpm, and C at that to maintain 160 bpm. The subject always started at a rate of 120 bpm, followed by 140 bpm, then 160 bpm. Duration of exercise was 5 minutes. While working, the rider wore shoes, socks, and shorts. The upper trunk was bare except for the heart rate electrode taped to the chest. Self-assessments were filled out immediately upon completion of each exercise regimen.
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RESULTS The data in Table 1 summarize ratings made on the five psychological scales by the 8 subjects while working in room temperatures of 26°C 8 ° C or - 10°C when rate of work was sufficient to raise cardiac frequency to 120 bpm, 140 bpm, or 160 bpm. Notice that in all but one of the 24 cases, feelings of exertion also increased when heart rate was increased at a particular temperature. This was what would be expected using Borg's scale. Of greater interest is that RPE ratings changed with temperatures when heart rate was held constant at 120 bpm, 140 bpm, or 160 bpm. The data in Table 1 indicate that perceived effort decreased significantly as temperature declined. The result was particularly reliable for the condition of greatest physical exertion (160 bpm), at which all subjects showed the same effect. lnterpreting this in the language of the scale indicates that effort diminished as temperature shifted from 26°C to - 10°C from something near very hard to a state situated between hard and somewhat hard. Data averaged over subjects, depicted in Figure 1, shows a progressive increase in perceived effort for each of the heart rates as the temperature rose. The closest correspondence between RPE ratings and heart rate was at 26°C. ie, the only thermal environment in the range of comfortable indoor temperatures as defined by engineering standard^.^ Note that when the average RPE ratings made at 26°C are multiplied by 10, the product approximates heart rate. Considering the differences in the age of our subjects and the original middle-aged standardizing group, the outcome for the 26°C condition was consistent with Borg's fir~dings.'~ Ratings on the Thermal Impression Scale indicated that average perceptions of the three thermal environments bore an ordinal relation to ambient temperature changes for each of the three conditions of physical work (heart rates), as expected. It also appeared that thermal impressions were reliably affected by workload. At all three temperatures, with one minor exception, the environment was rated warmest when heart rate was highest. The order of ranks was highly reliable at all three temper-
Spring 1991
atures. It appeared that exercise affected the impression of the warmth of the physical surroundings. In addition, thermal impression was highly correlated with changes in RPE, confirming that workload had a great effect upon the acceptance of the t h e d environment. In ordinary language, the thermal environment changed from being cool to being neutral (comfortable) when RPE increased from moderate to heuvy levels. Discomfort had a less simple relation to heart rate. Figure 1 shows that as heart rate increased, discomfort ratings increased so long as temperatures were 8°C or 26°C. However, when temperature dropped to - 10°C. the order of ratings of discomfort were altered, the highest being when the heart rate was slowest, presumably because the lightly clad bicycle riders became chilled (rated the thermal environment as cool). Given present perspective, the most important outcome was the sizable and reliable decrease in discomfort (increase in comfort) that occurred when temperature was reduced in the 160 bpm condition. Expressed in terms of the verbal scale, the average discomfort experienced doing the hardest work moved from being definitely uncomforlable to a position between slight and minimal discomfort as temperature decreased to - 10°C. It is interesting to note that the greatest discomfort in absolute terms was reported by Subjects 4 and 6 when their heart rates were 160 bpm and the air temperature was 26°C. Pace judgments were consistent over heart rates at all temperatures. At each temperature, the participants had to pedal most rapidly to maintain their heart rate at 160 bpm. This physical fact was present in subject ratings, which argues for the validity of the scale, but a new fact emerged when subjects' impressions of their nearness to maximum speed were compared across temperature conditions at each heart rate. The subjects were prone to judge their rate of pedaling to be close to their maximum capacity at high temperatures for the 160 bpm heart rate (see Figure I). The most optimistic self-perceptions were associated with the lowest temperature and 120 bpm. Comparing across temperatures shows that all 8 subjects rated themselves as farthest from maximal pedaling speed at the lowest temperature, ie, they all felt that they could increase their speed most at - 10°C. It was surprising and somewhat disturbing to note that, in spite of the considerable cardiac stress subjects were being subjected to at a heart rate of 160 bpm, all in the - 10°C condition judged that they were pedaling at less than 75% of maximum; and Subjects 2 and 7 actually considered themselves to be performing at or less than 50% of maximum. In sum, those working in a low temperature felt that they had considerable reserve to draw upon if they should de-
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FIGURE 1 Graphic Representation of the Relationship Between Temperature, Heart Rate, and Averages of Five Types of Self-Assessments Given by 8 Subjects.
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2o
1
I
140
160
r
I 140
Heart Rate (BPM)
Heart Rate (BPM) 20
-
20 -
18
-
18 -
16
-
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TABLE 1 Ratings of Perceived Effort, Thermal Sensation, Discomfort, Pace, and Endurance Given by 8 Subjects AfIer Performing 5 Minutes of Cycling on a Wind Trainer in One of Three Temperatures While Maintaining Head Rate Constant at 120,140, or 160 Beats per Minute
Subject
Effort 120 140 160
Thermal 120 140 160
26°C 1 2 3 4
12 10 12 11
5
11
15 17 15 17 15 17 12 15
17 17 17 18 18 17 I5 17
14
6 7 8 8°C 1 2 3 4 5 6 7 8 - 10°C 1 2 3 4 5 6 7 8
18 17 16 18 15
12 12 12
14 15 14 15 13 13 14 14
12 10 12 8 11 11 11 12
13 13 13 16 12 14 13 14
17 15 15 17 14 17 15 19
9 9 9 7 9
12 12
II
10 12 12
I5 15 12 15 13 12 13 14
9 10
10
12 11
15 16 18
11 15
13 9 12 10 14 11 11 7 8 7 11 11 7
Discomfort 120 140 160
Pace 120 140 160
18 18 18 19 19 19 18 19
10 7 11 12 12 14 9 9
12 10 13 16 16 15 11 13
14 15
10 9 13 10
16 17 15 18 15 16 13 16
18 18 17 19 19 15 16 18
9 6 9 11 7 9 8 8
10
13 14 13 15 14 13 14 13
11 10 10 11 12
12 12 7 10 9 11 13 8
13 13 8 15
10 8 12 15 13 8 8 13
11 9 11 13 11 9 9 12
12 10 10 14 10 12 13
11
14 16 10
1
cide to increase their rate of performance, notwithstanding their high heart rate, of which, of course, they lacked objective knowledge. Projected endurance judgments reinforced the conclusion that low temperature distorted judgments of personal capability. On the one hand, we found a benign relationship between projected endurance and heart rate when temperature was held constant. That is, projected endurance declined as heart rate increased in each thermal environment. This was also demonstrated by the fact that the median rating for all heart rates was 6 for 120 bpm, but 13 for 160 bpm. However, the bynow-familiar pattern again unfolded when we studied the relationship of projected endurance to temperature. Estimates of how much longer the rider could last in-
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11 11 13
11 14 11
10
I5 17 16 17 15 16
11
Endurance 120 140 160
15 17
8 13 13 8 6 9 6 6
10 14 16 14 7 II 12 7
13 16 18 17 10 13 14 10
10 12
12 12 13 18 16 13 13 14
16 14 15 17 17 16 16 16
6 11 12 10 6 7 6 6
10 13 15 13 7 10 12 7
13 I5 17 17 8 13 13
9 8 9 7 10 13 9 9
12 I1 11 10 13 14 12 12
15 12 14 I5 15 15 13 15
6 11
6 13 13 12 9 9 6 6
9 14
11 11
9 11
10
15 12
15 16 16 14 13 14
17 17 16 19 18 18
10
6 6 6 6 6
10
15 15 12 7 7 7 I
creased as the temperature declined at all three workloads (heart rates; see Figure 1). In the most demanding condition, the estimate doubled when temperature was reduced from 26°C to - 10°C. The word equivalents to the scale values are informative. When the scale values given in Table 1 are translated into words for an environment of - 1O"C, they disclose that half of the subjects whose heart rate was 160 bpm believed themselves to be capable of continuing for 50 minutes or more and that Subject 5 regarded the stress so minimal that he might continue indefinitely. In contrast, the identical subjects working in the temperature of 26°C with heart rate 160 bpm judged themselves as capable of continuing for a much shorter period, that is, continuing only 5 to 45 minutes longer.
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DISCUSSION
The average self-assessment made immediately after vigorous exercise in temperatures ranging between 26°C and - 1O"C, indicates that (1) reducing the temperature diminished the awareness of effort from a condition near very hard to one between hard and somewhat hard; (2) assessment of the thermal environment moved from cool to comfortable as heart rate was increased in the - 10°C condition; (3) the level of experienced discomfort decreased from uncomfortable to a position between slight and minimal discomfort at - 10°C; (4) subjects whose heart rate was 160 bpm judged that they were performing at less than 60% of maximum capacity at - 10°C v judging that they were over 80% maximum at 26°C; and ( 5 ) half of the subjects working in the - 10°C environment believed that they could maintain a pace of work producing 160 bpm for 50 minutes or more, whereas none of these same persons working at 26°C held this opinion. It is clear from their ratings that participants felt more confident of their abilities and were more Comfortable in the cool environment. A conclusion that these experiments demonstrate that the accuracy of perceptions of work done or work that could be done are significantly influenced by environmental temperature, however, would rest upon an assumption that the same amount of work was being done at each of the selected pulse rate and temperature combinations. Because measurements of physical or physiological work were not made, such an assumption may be unjustified, but there is some evidence suggesting that this might be true. One of the factors affecting the relationship of RPE and heart rate is temperature. Pandolf and colleagues6 increased heat stress and found that heart rate and RPE increased at disproportionate rates. Bergh19 studied both elevated and depressed body temperature in relation to several types of work and found systematic changes in RPE and heart rate. Bergh attributed these to several types of biological change that occur at different rates, depending upon the way environmental contact is made. Thus, the evidence is reasonably consistent that persons are unequally aware of their internal state and work potential in comfortable and cool environments. If this is to be extrapolated to an individual exercising in the cold, additional factors must be considered. One is that the body temperature of a person clad to maintain a feeling of comfort in the cold is likely to increase when physical work is in progress. Another is the effect of a cold environment on exposed skin and mucous membranes. There is a progressive reduction in heart rate when
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the surface of the face, particularly of the forehead, is exposed to increasingly lower temperatures,16and heart rate influences the perception of exertion, as Borg" pointed out. The matter is not simple, however, at either the physiological or the psychological level. Riggs et al" found that the relationship of ambient temperature and heart rate progressively changes within one period of exertion in ways apparently determined by ambient temperature. Other researchMhas demonstrated that heart rate, RPE, and thermal sensation all declined as a result of acclimatization to heat. As Pandolf'l suggested, heart rate per se may not be the major determiner of perceived exertion during exercise. In addition to attempting to identify new mediators for RPE, consideration might be given to an alternative definition of the dependent variable. The awareness of psychological factors such as type of physical a~tivity,~ time experience, thermal awareness, rate of performance, and perceived locus of muscular discomfort are among those items deserving more attention. A solution to the problem of perception of effort may require an approach deviant from that in use since 1%2. One alternative is to pursue a hierarchical model to explain perception of effort, an approach effectively used for muscular fatigueU and sedentary work fatigue.*' Another would be similar to that taken by Rohles and Millikenu for comfort perception. Their comfort scale is in semantic differential form, derived from a factor analytic procedure and scored using ratings and dimensional loadings. CONCLUSION
Physical competition encourages players to drive their physiological capabilities to their limit, and obsessive persons may feel a task once started must be completed. Body signals are assessed to determine those limits. The results of our study suggested that the assessment of physiological resources varied depending on both the work itself and the thermal environment in which exertion has taken place. Among the body signals used, heart rate may be unreliable. The results indicated several instances wherein self-perceptions were clearly wrong and, if acted upon, would stress the cardiac system significantly. This experiment was conducted with healthy young subjects. It is interesting to consider the implication of the results for persons with impaired cardiovascular function who work or exercise in a cold environment. The potentially misleading perception of well-being could lead to overwork or overexercise. An oxygen debt associated with cooling of environment and resulting re-
Behavioral Medicine
NELSON ET AL
distribution of blood flow and temporary metabolic acidosis could also lead to sudden cardiac dysfunction. The misreading of body signals is thought to play a role in the causation of sudden cardiac death.=*%Future studies will attempt t o clarify the relationship between work done, perception of work done, perception of work potential, body ambient temperature, and environmental temperature. INDEX TERMS cold, exedoa, fatigue, beut rate, pemptioa, temperature
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NM CONSENSUS PANEL REPORTS National Institutes of Health consensus development statements on Treatment of Early-Stage Breast Cancer and on Intravenous Immunoglobulin: Prevention and Treatment of Disease are available from the NIH Office of Medical Application of Research (OMAR), Building 1, Room 260, 9OOO Rockville Pike, Bethesda, MD u)892 (301) 4S1143. The conference on breast cancer was held in May 1990, that on intravenous immunoglobulin in June of the same year. At NIH, consensus conferences bring together researchers, practicing physicians, representatives of public interest groups, consumers, and others to cany out scientific assessments of drugs, devices, and procedures in an effort to evaluate their safety and effectiveness.
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