Psychosomaric Research,

Journal of Printed in Great

Vol. 35. No. 2/3, pp. 225-230,

1991. 0

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0022%3999/91 $3.00 + .oO 1991 Pergamon Press plc

EFFECTS OF AN ACUTE BOUT OF AEROBIC EXERCISE ON CARDIOVASCULAR AND SUBJECTIVE RESPONSES DURING SUBSEQUENT COGNITIVE WORK JANINE DYCK FLORY and DAVID S. HOLMES (Received 3 August 1989; accepted in revised form 23 August 1990)

Abstract-The experiment was conducted to test the effects of an acute bout of aerobic exercise on cardiovascular arousal and mood during a subsequent period of cognitive work. Each subject participated in two testing sessions, one that followed exercise and one that did not. In each session the subjects studied for 40 minutes, and arousal during the study period was assessed. The results indicated that prior exercise resulted in higher pulse rate (10%; p = 0.02), slightly lower systolic blood pressure (2%; p = 0.09), and higher feelings of vigor (59%; p = 0.01) than did no-exercise. The results are somewhat inconsistent with anecdotal reports concerning the effects of acute exercise, and possible reasons for the inconsistencies are discussed.

INTRODUCTION

THERE are numerous

anecdotal reports that an acute bout of aerobic exercise leads persons to feel less tense and more relaxed. This has been referred to as the ‘feeling better’ effect [l] or the ‘tranquilizer’ effect of acute exercise [2]. However, the experimental evidence for the arousal reducing effects of exercise is somewhat limited, and the evidence that does exist must be divided into two groups.* In the first group, the research was focused on the effects of exercise during subsequent periods of inactivity. The results of that research revealed that, when compared to no exercise, exercise resulted in a decreased level of EMG activity [3] but increased pulse rate [4, 31 and blood pressure [4]. With respect to subjective reports, acute aerobic exercise resulted in greater reductions in negative mood [5, 61 and greater increases in positive mood [7]. However, some researchers reported equal reductions in negative mood following periods of acute exercise and non-exercise [l, 81. In the second group, the research was focused on the effects of exercise during subsequent periods of stress. This is of interest because some persons report that acute exercise helps them prepare for a stressful period. The results of this research revealed that. when compared to no exercise, exercise did not lead to differences in EMG activity [3,9, lo] or subjective reports of mood [5,9], but exercise did lead to higher pulse rates [3,9]. It might be noted that in one recent experiment it was found that subjects who had or had not exercised did not differ reliably in their pulse rate and blood pressure responses during subsequent cognitive stress [6]. The fact that Author to whom correspondence should be addressed: David S. Holmes, Psychology Department, Fraser Hall, University of Kansas, Lawrence, KS 66045, U.S.A. *When reviewing the previous experiments on the effects of acute bouts of exercise, it is important to note that many suffer from methodological problems that preclude our drawing conclusions from the data. These problems include the non-random assignment of subjects to conditions [22Z251, the failure to include a non-exercising control condition with which to compare the effects of exercise [26, 1,27-311, and the fact that effects of exercise have been confounded by the effects of the warm showers that were taken after exercise [32]. Other investigations were reported only in abstracts, and the brevity of the reports makes it impossible to assess the procedures or results [33-361. 225

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D. S. HOLMES

these results differ from the earlier results concerning pulse rate may be due to the fact that the subjects participated in relatively mild exercise (1 15- 135 bpm for 20 min) or the fact that the subjects rested for 20 min following the exercise so that their heart rates may have returned to baseline before the stress. Overall, there are very few data concerning the effects of acute bouts of aerobic exercise, and the data that do exist do not support the anecdotal reports of subsequently reduced arousal. However, it should be noted that most of the findings that have been reported are limited in the degree to which they can be generalized beyond the laboratory; that is, they lack external validity [I I]. The threats to external validity will be discussed later, and they may account for the failure of the results to match anecdotal reports. The present experiment was conducted to provide a more externally valid test of the physiological and psychological effects of an acute bout of aerobic exercise. In this experiment, female undergraduates either did or did not participate in a 40-minute aerobic exercise dance class that was typical of the classes many people attend. The students then studied for 40 min much as they normally would. During the study period, pulse rates and blood pressures were assessed. and the students reported their subjective feelings of anxiety, depression, vigor and fatigue. There are four ways in which the present experiment had more external validity than most of the previous research. First, the exercise was a typical aerobics class like that used by many of the persons who report the positive effects of exercise. In the ‘real world’ it is more likely that persons would use this type of exercise rather than the treadmill running or the other types of laboratory exercise that have been used in previous research. Second, the effects of the subjects’ exercise were compared to the effects of the subjects’ routine activities rather than to the effects of a period of controlled rest, In the ‘real world’ it is more likely that exercise would replace other activities than rest. Third, the effects of exercise were assessed during a subsequent period of cognitive work (studying) rather than during a subsequent period of inactivity or brief/intense stress. ln the ‘real world’ it is more likely that exercise would precede or be used to prepare for work than for rest. Furthermore, an extended period of normal cognitive work is probably more typical than a brief period of intense stress. Fourth, the cognitive work in which the subjects engaged was typical. real, and relevant work (they brought their own study materials) rather than a contrived labortory task. It is possible that the work brought by subjects demanded differing levels of effort, but that reflects the ‘real world’.

METHOD

The subjects were 18 female undergraduate students who were enrolled in rhythmic aerobic exercise classes at the University of Kansas. Twenty students were invited to participate: one could not participate because she did not have a free period following the class and one completed only the first part of the experiment.

E.Ycv~i.cc clu.v.v. The cxcrcise classes conslsted of approximately IO min of warm-up excrciscs, 20 min of aerobic dance. and IO min of cool-down exercises. All subjects were instructed to exercise with enough intensity to maintain their pulse rates at 60~80”/0 of their estimated maximum (determined by subtracting their age from 220). and there were occasional breaks during the dance phase of the class during which subjects monitored their pulse rates. Subjects reported a mean pulse rate of I55 bpm for the dance phase

Effects of acute exercise

227

of the class. The experiment was conducted after the first month of classes and therefore the subjects were accustomed to the routine. Testing sessions. Each subject participated in two testing sessions. Both sessions were identical except that the session for the exercise condition was conducted after exercise and the session for the no-exercise condition was conducted on a day when the subject did not exercise. The session for the exercise condition was conducted approximately 15 min after the subject had participated in an exercise class. the no-exercise condition session was conducted on another day on which the subject was allowed to miss the exercise class and instructed not to exercise. Order of participation in the two conditions was counterbalanced across subjects. When a subject arrived for a testing session, she was taken to a research room in the exercise physiology laboratory where she was seated at a desk, informed about the procedures to be used in the session and asked to sign an informed consent statement (none refused). The cuff from a Critikon vital signs monitor (Model 8100) was then placed on the subject’s right arm. Next the subject was asked to sit quietly and study for 40 min. (When the subject was originally contacted about the experiment, she was told about the study period and instructed to bring materials to study.) The experimenter then left the room. Every fourmin during the 40-min study period the vital signs monitor automatically measured the subject’s systolic blood pressure, diastolic blood pressure and pulse rate. The data were stored in the monitor’s memory bank. At the end of the study period, the experimenter re-entered the room and asked the subject to complete the Multiple Affect Adjective Checklist (MACL; 12) and the Profile of Mood States (POMS; 13). The subject was asked to respond to the questionnaires in terms of how she felt during the study period. The MAACL was used to assess anxiety and depression and the POMS was used to assess vigor and fatigue. At the conclusion of the second test session, the nature of the experiment was completely explained to the subject.

RESULTS

&fSects of exercise

on physiological

arousal during the study period

To assess the effects of exercise on physiological arousal during the study period, a 2 (exercise, no exercise) x 10 (Cmin measurement intervals) repeated measures analysis of variance was conducted on each physiological measure.* The analysis of the pulse rate data revealed that subjects had reliably higher pulse rates following exercise than no-exercise, F(1,17) = 6.37, p = 0.022 (MS = 82.75 vs 75.56 bpm). The analysis also indicated that in general pulse rates declined across measurement intervals, an effect that probably reflects simple adaptation to the situation, F(9,153) = 4.79, p < 0.001. Finally, a reliable condition by intervals interaction reflected the fact that the difference in pulse rate between the exercise and no-exercise conditions diminished over time, F(9,153) = 1.94, p = 0.050. These results are presented graphically in Fig. 1. The analysis conducted on the systolic blood pressure data indicated that following exercise the subjects tended to have lower systolic blood pressure than they did following no exercise, F( 1,17) = 3.24, p = 0.090 (MS = 106.89 vs 108.80 mmHg). The analysis also revealed a reliable decline in pressure across intervals, an effect that was probably due to adaptation, 1;(9,153) = 5.98, p < 0.001. There was not a reliable conditions by intervals interaction, F(9,53) = 0.84. These results are presented graphically in Fig. 2. The analysis of the diastolic blood pressure data did not reveal any reliable effects or trends: conditions F( 1,17) = 0.53, intervals F(9,153) = 0.64, conditions by intervals interaction F(9,153) = 0.85. *To determine whether order of conditions (exercise first orno-exercise first) influenced the results an initial series of analyses was conducted in which order was included as a variable. None of these analyses revealed any reliable interactions involving order and therefore it can be concluded that order did not influence the results.

J. DYCK FLORY and D. S. HOLMES

114

%_ -.

1

NO EXERCISE

0 .‘-------

,~___--____-__’

3

I

NO EXERCISE

EXERCISE

5

1

7

9

FOUR MIN INTERVALS FIG. 1. Pulse rates

FIG. 2. Systolic

no-exercise

exercm

@f&s

; : : : : :

for subjects in the exercise and conditions during 40-min of cognitive work (studying).

of’ exercise

3 5 7 9 FOUR MIN INTERVALS

blood pressure for subjects in the and no-exercise conditions during 40-min of cognitive work (studying).

on subjectir.e urousul during the .vtucQ period

To assess the effects of exercise on subjective arousal during the study period, a simple repeated measures (exercise, no-exercise) analysis of variance was conducted on each self-report measure. Those analyses indicated that subjects reported reliably more vigor after exercise than after no exercise, F( 1.16) = 7.61, p = 0.014 (MS = 15.06 vs 9.41). There were no differences in depression, F( 1,16) = 0.84, anxiety F( I ,16) = 0.45, or fatigue F( I, 16) = 0.05. DISCUSSION

The procedures used in this experiment closely approximated the activities in which persons engage outside of the laboratory (i.e. exercise classes and studying). Despite that, the effects generated by the experiment were inconsistent with the anecdotal reports that acute aerobic exercise leads to relaxation and reduced subjective arousal. Indeed. on days when subjects studied after exercising they showed pulse rates that were almost 10% higher than days when they studied after normal (non-exercise) activities. Furthermore, following exercise the subjects reported subjective levels of vigor that were 59% higher than those reported following normal activities. (Both the pulse rate and vigor effects were statistically reliable.) Systolic blood pressure tended to be somewhat lower following exercise than normal activities (the effect approached statistical reliability). but the difference was less than 2% and was probably inconsequential. It is interesting to note that comparable results were produced in a recent multiple-baseline experiment in which on alternate days of an eight-day period a physically fit middle-age male either ran seven miles or did routine household tasks before working on his computer for two hours [14]. Measurements taken throughout the 2-hr work period revealed that relative to no-exercise days, on exercise days he showed a pulse rate that was 22% higher and systolic blood pressure that was only 4% lower. These findings suggest that the results of the present experiment are not unique to the subject population or level of exercise used.

Effects of acute exercise

229

Despite the fact that these and other laboratory findings are inconsistent with the anecdotal reports, it does not seem appropriate to reject the anecdotal reports. Rather, it may be that investigators have been examining the wrong variables. Attention has been focused primarily on cardiovascular responses (probably because they have been shown to be influenced by chronic exercise), but the effects of acute exercise may be mediated by changes in electromyographic activity [e.g. 2, 31. It is also possible that the reported relaxation effect is due to an increase in endorphin levels. It should be noted, however, that thus far investigators have been unable to link changes in endorphin levels to changes in mood [15-171. With respect to the subjective effects of exercise, it may be more appropriate to assess potential increases in relaxation/sedation (positive mood) rather than decreases in anxiety (negative mood) because these may tap different dimensions. Increases in relaxation/sedation are not necessarily incompatible with the invigoration effect that was found in this study. In other words, following acute exercise persons may feel relaxed but invigorated and ready to work. These possibilities deserve laboratory investigation. Finally, the results of this and other investigations highlight the importance of distinguishing between the effects of acute bouts of aerobic exercise and the effects of chronic aerobic exercise or high levels of aerobic$tness. Acute exercise appears to result in increased cardiovascular arousal during subsequent periods of rest and stress, whereas chronic exercise and fitness result in decreased cardiovascular arousal during rest and stress [e.g. 18-211. REFERENCES 1. 2. 3. 4. 5.

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Effects of an acute bout of aerobic exercise on cardiovascular and subjective responses during subsequent cognitive work.

The experiment was conducted to test the effects of an acute bout of aerobic exercise on cardiovascular arousal and mood during a subsequent period of...
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