Journal of Psychosomatic Research. VoL 34, No. 6, pp. 629-636, 1990.
0022-3999/90 $3.00 + .00 ~i 1990 Pergamon Press plc
Printed in Great Britain.
THE
EFFECT
OF
EXERCISE
ON
NORMAL
MOOD
SHELLEY S. LENNOX, JEFFREY R. BEDELL a n d ARTHUR A. STONE* (Received 19 July 1989; accepted & revisedform 4 April 1990)
Abstract--Research has shown that aerobic exercise is effective in alleviating depression. However, the contention that aerobic exercise similarly has an enduring beneficial psychological effect on the mood of normal, non-depressed individuals has not been verified. Research examining the effects of exercise on normal mood has yielded inconsistent findings, due in part to methodological shortcomings. The present study attempted to rectify these methodological difficulties and evaluated the effect of 13 weeks of aerobic exercise on the mood of normal, non-depressed men and women. Groups intended to be non-aerobic and waiting list controls were included in the design, as were a stratified random sampling procedure, measurement of physical fitness, and a seven-day pre/post-program assessment period for both positive and negative mood. Results indicated that, although subjects demonstrated significant improvement in physical fitness, there were no significant changes in either positive or negative mood. Thus, in contrast to effects with clinical depressives, exercise does not appear to have any long-term beneficial effect on the mood of non-depressed individuals selected from a normal, i.e. non-clinical, population.
INTRODUCTION RESEARCH d e m o n s t r a t i n g the beneficial effects o f a e r o b i c exercise on physical health [1, 2] has led to m e n t a l health applications. Such research has clearly indicated that a e r o b i c exercise can reduce the s y m p t o m s o f depression [3]. Results with depression have been interpreted to suggest that exercise will also e n h a n c e the m o o d a n d vigor o f n o r m a l , n o n - d e p r e s s e d individuals. H o w e v e r , the literature e x a m i n i n g this h y p o t h esis is s o m e w h a t difficult to interpret given inconsistent findings, due in p a r t to m e t h o d o l o g i c a l s h o r t c o m i n g s . T h e r e is currently little definitive scientific evidence to s u p p o r t or refute the c o n t e n t i o n that a e r o b i c exercise has e n d u r i n g beneficial p s y c h o l o g i c a l effects on the m o o d o f n o r m a l , n o n - d e p r e s s e d individuals. Earlier studies 1970-1982
W i t h some exception [4, 5], much o f the p r e l i m i n a r y research that e x a m i n e d the effects o f exercise on n o r m a l m o o d was c h a r a c t e r i z e d by significant m e t h o d o l o g i c a l p r o b l e m s that preclude i n t e r p r e t a t i o n o f findings. Investigators: (a) allowed subjects to self-select whether they w o u l d a t t e n d exercise or c o n t r o l p r o g r a m s [6, 7]; (b) used c o r r e l a t i o n a l designs that precluded causal statements regarding m o o d a n d exercise [8-1 I]; (c) simply c o m p a r e d the m o o d o f people who exercised regularly with those w h o did not, w i t h o u t c o n s i d e r a t i o n o f the biased n a t u r e o f such g r o u p s [10, 12]; (d) e m p l o y e d g r o u p designs with i n a d e q u a t e o r no c o n t r o l s [9, 13, 6, 7); (e) c o n d u c t e d exercise p r o g r a m s t o o short in d u r a t i o n to optimize physical fitness changes [7]; a n d / o r (f) failed to either m e a s u r e or r e p o r t changes in physical fitness [6, 7]. U n f o r t u n a t e l y , the two well designed studies [4, 5] excluded w o m e n a n d were Albert Einstein College of Medicine, Yeshiva University, New York, U.S.A. Mailing Address: Shelley S. Lennox, Ph.D., Department of Psychiatry, Albert Einstein College of Medicine, Yeshiva University, 2527 Glebe Avenue, Bronx, NY 10461 U.S.A. *Department of Psychology, State University of New York at Stony Brook, Stony Brook, New York, U.S.A. 629
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SHELLEY S. LENNOX et al.
conducted immediately post-myocardial infarction, thus limiting the generalizability of findings to male cardiac patients. Methodological problems were also accompanied by inconsistencies in findings. For instance, some studies reported either superior mood in regular exercisers or mood enhancement following an aerobic exercise program [6, 10, 14], while others failed to observe effects [7, 8]. Moreover, some investigators observed that, with ostensibly normal samples, i.e. individuals not selected from a psychiatric population, beneficial psychological change occurred primarily for those with the worst psychological and/or physical status (see Ref. 15 for brief review). However, there is some indication that these individuals were, indeed, clinically depressed and, therefore, mistakenly included in the 'normal' samples. Recent studies 1983 to present
Recent years have witnessed the emergence of a number of studies that have attempted to rectify many of the methodological problems mentioned. With some exception [16]. investigations conducted over the past seven years have incorporated randomized trials and physical fitness assessment in their designs. Inconsistent findings, however, have still been observed. Although the reason(s) for these discrepancies is not immediately apparent, the studies do vary on several potentially relevant variables, one of which is the subject sample assessed. Although all the studies evaluated for the present investigation purportedly selected participants from the 'general' population, two required that candidates demonstrate clinically significant anxiety upon admission [17, 18]. Obviously, the positive mood findings with these samples cannot be used to support the hypothesis that exercise induces mood improvement in psychologically 'normal' individuals. The remaining studies found in the literature all sampled from non-clinical populations, however, three of them excluded women [19 21]. Findings observed in these studies were mixed, with three of them reporting no reduction in depression [21-23], one reporting inconsistent effects [19], and another reporting improvement in subjective well being [20]. The findings of Hughes, Casal and Leon [21], however, are particularly questionable as their training program appears to have produced minimal change in functional capacity (duration of time on treadmill (rain.) pre-program = 10.9, post-program = 11.1). In addition to sample differences, recent studies also vary in the degree to which they control extraneous variables. For example, excluding the two investigations that evaluated individuals with clinical disorder [17, 18], one study did not control for the passage of time [19], others failed to control for involvement in non-aerobic activity [21-23], while another did not control for either of these factors [20]. Interpretive difficulties also arise from assessment procedures that are neither uniform nor adequately described. In many instances, investigators have not indicated when, in relation to the exercise session, post-program mood measures were completed [19-21]. If measurement followed immediately upon the exercise session (even if it was not a state measure), it would have been biased toward reflecting the short-term and transitory effects of exercise. As the research question of interest is whether regular exercise produces persistent (not transitory) mood change, measurement of mood distant in time from the episode of exercise is essential
The effect of exercise on normal mood
631
Obviously, despite improvement in the methodological rigor of recent studies investigating the effect of regular aerobic exercise on the mood of normal individuals, interpretive difficulties remain. Differences in samples and control of extraneous but relevant variables, as well as variability in assessment procedures, all contribute to the problem. In addition, although recent exceptions hopefully represent a trend [20, 22], investigators have typically used dependent measures that emphasize evaluation of changes in negative mood (primarily depression and anxiety) [19, 21]. Since the mood of 'normals' is generally defined by the absence of significant depression or anxiety, scales based on the measurement of negative mood alone leave little room for non-depressed individuals to report improvement since a ceiling effect is encountered. Use of scales designed to measure 'positive mood' is essential when evaluating the effects of exercise on the mood of normal individuals.
The present study The purpose of the present investigation was to employ a research design and methodology that would help rectify some of the methodological difficulties cited, and to evaluate the effect of regular aerobic exercise on the mood of non-depressed individuals. To achieve this objective, we evaluated the effects of a substantial period of exercise training (i.e. 13 weeks) on the mood of physically and psychologically healthy adult volunteers. To control for unmanipulated yet outcome-related variables, a waiting-list group and a group designed to engage in non-aerobic exercise were also included in the study. Subjects were assigned to the three experimental conditions by means of a stratified random sampling procedure. To verify the aerobic manipulation, physical' fitness was assessed before and after the 13-week program. To increase reliability and the probability of evaluating relatively persistent mood effects, post-program mood was assessed for seven days, well after the transitory effects of exercise has subsided. Finally, we used measures of positive as well as negative mood, and included both men and women in the study, enabling the evaluation of sex effects. METHOD
Sul~jects Seventy employees of the Veterans Administration Medical Center in Northport, LI, volunteered to participate in an exercise program ostensibly conducted for the purpose of reducing the risk of heart attack. Subjects were assigned to experimental conditions using a stratified random sampling procedure. They were first matched on sex, positive and negative mood (as assessed by the Multiple Adjective Checklist, M A C L , [24], and the Depression Adjective Checklist, DACL, [25]), and physical fitness (funtional capacity), then randomly assigned to the walk-jog (W J), volleyball/weight lifting (VB), or waiting-list control groups. Forty-seven subjects, 15 each in VB and WJ (both containing nine females and six males) and 17 in the control group (11 females, six males), completed the study, with 23 of the original volunteers (10 VB, nine W J, four controls) terminating participation in the program. The most c o m m o n reason for termination was work schedule conflict. Comparison of subjects who completed the program with those who did not revealed no differences in age, education, marital status, or sex. There were no significant differences in the percentage of drop-outs a m o n g the three groups. The mean ages of male and female participants were 43 and 47 yr, respectively. With the exception of one S (who had undergone coronary bypass surgery three years prior to the study), no subject had experienced a myocardial infarction or reported a history of heart disease. All were negative for ischemia on the stress test. All participants denied involvement in regular exercise (of at least 15 rain duration three times per week) and scored below 10 on the Beck Depression Inventory-short form (BDI), [26], the criterion used to eliminate prospective participants with clinically significant depression.
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SHELLEYS. LENNOXet al.
~leasures Physicalfimess assessment. The primary measure of physical fitness was functional capacity, defined as the number of minutes the subject walked or walked/ran from start to voluntary termination of exercise (voluntary maximum) on the treadmill stress test. Performance was evaluated with the Bruce Protocol [27] (Burdiek Stress Test Machine, System IIl Channel EXTOT, Three Channel Electrocardiograph, EK670). Sel/2report inventories o[" depression and mood. The Beck Depression Inventory-short form (BDI) was used to evaluate the presence of clinically significant depression. With well documented psychometric properties, the BDI consists of 13 multiple-choice items and yields a score ranging from 0 to 39, with higher numbers reflecting greater depression. The Depression Adjective Checklist (DACL) consists of 26 adjectives that assess depressed mood. Scores range from 0 to 26, with higher values reflecting more dysphoria. The Mood Adjective Checklist (MACE) is a 33-adjective checklist that measures positive and negative mood states. The seven factors comprising these mood states include sadness, anxiety, aggression, fatigue, surgency, vigor and elation, The first four factors represent negative affects and were combined to form a composite measure of dysphoria, while the last three represent positive affects, and were combined into a measure of euphoria.
Procedure Upon entry into the study, subjects underwent a stress test to voluntary maximum, were administered the BDI, MACL and D A C E and then assigned to the WJ, VB, or waiting-list group. The MACL and DACE were completed at the end of the day for seven days prior to commencement of exercise. The mean of the seven daily scores served as the dependent measure of pre-treatment mood. Subjects assigned to the exercise conditions (WJ or VB) met for 50-450 min three times per week for 13 weeks, and two instructors led each group. Exercise groups started with 5-10 rain of stretching, then proceeded with assigned activity. Subjects in the WJ (aerobic) group utilized individualized exercise prescriptions that attempted to have S walk or jog at 70 80% of heart rate capacity (as determined on ttle pre-program stress test) and expend approximately 300 calories per session. This was accomplished by first computing 56 70% of the maximum oxygen consumption (equal to 70 80% of maximum heart rate) estimate derived from the stress test, and then converting this to a measure of speed. Calorie requirements per minute, based upon body weight and speed of walking or jogging, were then computed and divided by 300 to determine the duration of exercise required to consume 300 calories [28, 29]. A quarter-mile cement walkway around a courtyard served as the main track. Subjects in the VB group (designed to function as the non-aerobic exercise condition) engaged in 10 15min of weight lifting and calisthenics, followed by 30 35 rain of volleyball. Weight lifting and calisthenics were selected as activities because of their known failure to produce aerobic training effects [30]. Although power or competitive volleyball will produce cardiovascular benefit, the recreational nature of the game planned for our inexperienced subjects was not expected to result in significant changes in aerobic capacity [31]. To increase the similarity of WJ and VB members' experience of mastery and accomplishment, the weight lifting and calisthenics component of the program included progressive increments in difficulty, with modification of individualized regimens determined jointly by subject and group leader. The waiting-list control subjects were instructed to refrain from involvement in regular exercise for the 13-week study period, and were informed that an exercise program would become available to them at that time. Within a week of termination of the exercise progranr, all Ss again underwent a stress test to voluntary maximum, and completed the MACL and DACL at the end of each day for seven days.
RESULTS
Physical fitness A n a n a l y s i s o f v a r i a n c e ( A N O V A ) w a s u s e d to a s s e s s t h e effects o f g r o u p VB, c o n t r o l s ) , sex ( M , F ) a n d t i m e ( p r e , p o s t t r e a t m e n t ) o n f u n c t i o n a l c a p a c i t y o n t r e a d m i l l ) . T h e A N O V A y i e l d e d s i g n i f i c a n t m a i n effects o f sex ( F ( 1 , 3 8 ) = p < 0.013) a n d t i m e ( F ( 2 , 3 8 ) = 24.36, p < 0.001), a n d a s i g n i f i c a n t i n t e r a c t i o n
( W J, (time 6.71, effect
o f g r o u p a n d t i m e ( F ( 2 , 3 8 ) = 6.08, p < 0.05). T h e m a i n effect o f sex i n d i c a t e d t h a t m e n d e m o n s t r a t e d g r e a t e r f u n c t i o n a l c a p a c i t y t h a n w o m e n . T h e m a i n effect o f t i m e is b e s t u n d e r s t o o d in t e r m s o f t h e g r o u p x t i m e i n t e r a c t i o n . E v a l u a t i o n o f t h e m e a n s a s s o c i a t e d w i t h this i n t e r a c t i o n (see T a b l e I)
The effect of exercise on normal mood
633
TABLE I.-- MEANS AND STANDARD DEVIATIONS OF PRE- AND POST-TREATMENT FUNCTIONAL CAPACITY SCORES FOR SUBJECTS IN THE AEROBIC ( W J), NON-AEROBIC (VB) AND NO-EXERCISE CONTROL GROUPS
Functional capacity Type of exercise Aerobic (WJ) Non-aerobic (BV) No-exercise (Control)
n 15 15 17
Pre-treatment Post-treatment 9.79 (2.31) II.85 (2.24) 10.01 (2.14) 11.50 (2.19) 10.23 (1.83) 10.45 (2.14)
indicated that, while there were no significant differences in pre-treatment functional capacity among the three groups, significant improvement was observed post-treatment in the two exercise groups, both of which exhibited significant increases relative to controls (VB vs controls: F(1,24) = 5.6, p < 0.025; WJ vs controls: F(1,25) = 16.4, p < 0.001). Additionally, there was no significant difference in improvement between the WJ and VB groups, and no significant pre-post improvement in the no treatment control group. Positive and negative m o o d
Similar to functional capacity, each of the three mood variables (i.e. scores on the D A C L and the two subscales of the MACL) was evaluated with a group (W J, VB, control) by sex (M, F) by time (pre-post treatment) A N O V A with repeated measures on time. None of these analyses yielded any significant effects. Thus, there were no significant differences among groups, between sexes, or across time in (a) depressed mood or depressive symptomatology as measured by the D A C L or M A C L (dysphoria subscale), or (b) positive mood as measured by the M A C L (euphoria subscale). DISCUSSION The present study evaluated the effects of regular aerobic exercise on normal mood through an experimental design that attempted to eliminate many of the methodological inadequacies precluding clear interpretation of previous research findings. Current findings indicated that, although subjects demonstrated significant improvement in physical fitness, they did not evidence significant improvement in positive or negative mood. Thus, in contrast with clinical depressives, whose depression improves following aerobic exercise training, normal adults do not appear to experience such beneficial m o o d changes. The current findings, inconsistent with those observed by Brown et al. and Goldwater and Collis [6, 20], support the observations of King et al. [22] and Moses et al. [23], who found no reduction in depression following aerobic training. Morgan et al. [7], Folkins et al. [13], and Simons and Birkimer [16] similarly found no improvement in depression among non-depressed Ss, although they did observe such training-induced change in depressed individuals. It is of interest to note that the VB program, designed to function as the non-aerobic activity (and intended to control for effects correlated with a supervised group exercise program but not attributable to the aerobic nature of such exercise), produced increases in functional capacity similar in magnitude to those of
634
SHELLEY S. LENNOX et al.
walk-jogging. This finding indicates that we were not successful in producing a non-aerobic condition and, in effect, evaluated the efficacy of two different aerobic programs of varying intensity. (The group mean exercise heart rate as computed from the mean pulse value of each subject across the middle five weeks of the program was 65% and 83% of maximum for the VB and WJ groups, respectively.) It also suggests that, for sedentary individuals, regular involvement in activity that is generally not classified as "aerobic' can produce cardiovascular fitness improvement typically associated with activities so classified. Similar findings have been observed elsewhere [28]. It is possible that a more rigorous walk~og program, or a study period of longer duration, would have distinguished the groups. Although the present authors' failure to effectively include a non-aerobic group compromises the methodological rigor with which the study was conducted, several factors combine to support the validity of findings with regard to the hypothesis under consideration. First and foremost, the magnitude of increase in functional capacity for subjects in the exercise conditions was similar to that observed in other studies, even those of longer duration [2, 32]. Thus, an aerobic training effect was produced. Moreover, in the presence of this physical fitness training effect, mood change was not produced. The failure to include a non-aerobic group does not question the validity of this finding. Interpretive difficulties would have resulted only if mood changes had been observed. Under this circumstance, it would have been impossible to sort out the independent effect of the aerobic variable. The present study can also be faulted tbr its failure to evaluate subject expectancies. Given the potential relevance of this variable to mood outcome, its measurement should be included in all future research. The failure of the present study to observe increases in positive mood obviously needs to be reconciled with frequent reports of a euphoric experience after exercise. Given the latter, present findings appear to counter subjective reality. However, the two observations are not necessarily incompatible as they may, in fact, refer to different effects. Anecdotal reports of euphoria or exhilaration frequently refer to acute mood effects, i.e. those occurring during or immediately tbllowing an exercise session [33 36], whereas the current study evaluated the presence of more stable or persistent mood changes as a result of engagement in regular exercise over a sustained period of time. The latter is of much greater significance. Taken together, the findings seem to indicate that a bout of exercise may produce short-term improvement in the m o o d of normal individuals, but does not result in any persistent mood change. Moreover, in contrast to depressives, non-depressed individuals do not appear to experience any stable beneficial m o o d changes following participation in regular exercise over a sustained period of time. As indicated in the Introduction, a limiting factor of some previous studies was their failure to either measure, report, or possibly achieve, physical fitness effects [6, 7]. Since the efficacy of any aerobic exercise program is determined by measurable cardiovascular changes, evidence of physical fitness benefit is essential. Findings of the current study provide this evidence, with walk~oggers demonstrating significant increases in functional capacity. This suggests that the failure to observe mood changes was not the result of an inadequate training program. In conclusion, the literature suggests that exercise is at least a partial remedy for dysphoric mood in depressed individuals and may offer short-term elevations in the
The effect of exercise on normal mood
635
mood of normal, non-depressed individuals. The present study, however, indicates that the effects of exercise do not appear to have any long term beneficial effect on t h e m o o d o f n o r m a l i n d i v i d u a l s , e i t h e r t h r o u g h (a) t h e a l l e v i a t i o n o f d y s p h o r i a negative mood, or (b) enhancement of positive mood.
or
REFERENCES l. 2. 3. 4. 5. 6. 7. 8. 9. 10. I 1. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26.
PAEFENBARGERRS, BRAN[) A J, SHOLTZ RI, JUNG DL. Energy level, cigarette smoking, and blood pressure level as related to death from specific diseases. Am J Epidemiol 1978; 108:12 18. BONANNOJ, LIES JT. Effects of physical training on coronary risk factors. Am J Cardiol 1974; 33: 760 764. SIMONSAD, EPSTEIN HE, McGOWAN CR, KUPFER D J, ROBERTSON RJ. Exercise as a treatment for depression: An update, Clin Rev 1985; 5:553 568. PROSSERG, CARSONP, PHILLIPSR, GELSONA, BUCH N, TACKERH, NEOPHYTOUM, LLOYD M, SIMPSON T. Morale in coronary patients following an exercise programme. J Psychosont Res 1981; 25: 587 593. STERN M J, CLEARY P. The national exercise and heart disease project: long term psychosocial outcome. Arch Intern Med 1982; 142:1093 1097. BROWN RS, RAMIREZ DE, TAUB JM. The prescription of exercise for depression. Physician Sports Med 1978; 6: 35M.5. MORGAN WP, ROBERTS JA, BRAND FR, FEINERMANAD. Psychological effect of chronic physical activity. Med Sci Sports 1970: 2:213 217. HARTt;NG GH, FARGE E J, MITCHELL RE. Effects of marathon running, jogging, and diet on coronary risk factors in middle-aged men. Prevent Med 1981; 10:316 323. NOWLIS DP, GREENBERG N. Empirical description of effects of exercise on mood. Percept Motor Skillls 1979; 49:1001 1002. CARTER R. Exercise and happiness. J Sports Med 1977; 17:307 313. SNYDEREL, SPREITZEREA. Involvement in sports and psychological well-being. Int J Sport Psychol 1074; 5:28 39. WILSONVE, MORLEY NC, BIRD El. Mood profile of marathon runners, joggers, and non-exercisers. Percept Motor Skills 1980; 50:117 118. FOLK1NSCH, LYNCtt S, GARDNER MM. Psychological fitness as a function of physical fitness. Arch Phys Med Rehabil 1972; 53:503 -508. BAHRKEJS. Exercise, meditation and anxiety reduction: A review. Am Correct Ther J 1979; 33:41 4 4 . GREISTJH, KLEIN MH, EISCHENS RR, FARIS JT. Running out of depression. Physician Sports Med 1978; 6:49 56. SIMONSCW, BIRKIMERJC. An exploration of factors predicting the effects of aerobic conditioning on mood slate. J Psychosom Res 1988; 32:63 75. LONG BC. Aerobic conditioning and stress inoculation: a comparison of stress-management interventions. Cog Ther Res 1984; 8:517 542. STEPTOEA, EL)WARDSS. The effects of exercise training on mood and perceived coping ability in anxious adults from the general population. J Psychosom Res 1989: 33: 537-547. EMERYCF, BLUMENTHALJA. Effects of exercise training on psychological functioning in healthy type A men. Psychol Hhh 1988; 2:367 379. GOLDWA1"ERB, COLLIS M. Psychologic effects of cardiovascular conditioning: a controlled experiment. Psychosom Med 1985; 47:174 181. HUGHESJR, CASAL DC, LEON AS, Psychological effects of exercise: a randomized cross-over trial. J Psychosom Res 1986; 30:355 360. KING AC, TAYLOR CB. HASKELL WL, DEBUSK RF. Influence of regular aerobic exercise on psychological health: a radomized, controlled trial of healthy middle-aged adults. Health Psychol 1989: 8:305 324. MosEs J, STEPTOEA, MATHEWSA, EDWARDSS. The effects of exercise training on mental well-being in the normal population: a controlled trial. J Psychosom Res 1989; 33: 47~1. NOWLISV. Research with the mood adjective check list. In Affect, Cognition and PersonaliO,. (Edited by TOMKINS SS, IZARD CE). New York: Springer, 1965. LUBIN B. Fourteen brief lists for the measurement of depression. Arch Gen P,tvchiat 1965; 15: 205 208. BECKAT, BECk: RW. Screening depressed patients in family practice: A rapid technique. Povtgrad Med 1972; 52:81 85.
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SHELLEY S. LENNOX et al. BRUCERA, BLACKMANJR, JONESJW, STRAITG. Exercise testing in adult normal subjects and cardiac patients. Pediatrics 1963; October: 742 756. MCARDLE WD, KATCH FI, KATCH VL. E.:ercise Physiology in Energy Nutrition and ttuman Perlbrmance. Philadelphia: Lea and Febiger, 198 I. AMERICAN COLLEGE OF SPORTS MI~:DIC1NE. Guidelines .[~r Graded Exercise Testing and Exerci~'e Prescription, Second Edn. Philadelphia: Lea and Febiger, 1980. COOPERK. Aerobic update. Runner's World 1983; 18: 47, 72 75. ROSENZWEIG. Sport.sfitness fi)r Women. MANN GV, GARRETT HL, FARHI A. MURRAY [t, BILLINGS FT. Exercise to prevent coronary hcarl disease. Ant J Med 1969: 4 6 : 1 2 27. PARGMAND, BAKERMC. Running high: Enkaphalin indicted. J Drug Ls'sues 1980: Summer: 341 439. GLOVERB, SHEPHERD J, The Runner's ttandbook. New York: Penguin Books, 1978. STEPTOEA, COX S. Acute effects of aerobic exercise on mood. Health Psychol 1988: 7 : 3 2 9 340. STEPTOEA, BOLTONJ. The short-term influence of high and low intensity physical exercise on mood. Psychol HIth 1988; 2:91 96.
0022-3999/90 $3.00 + .00 ~i 1990 Pergamon Press plc
Printed in Great Britain.
THE
EFFECT
OF
EXERCISE
ON
NORMAL
MOOD
SHELLEY S. LENNOX, JEFFREY R. BEDELL a n d ARTHUR A. STONE* (Received 19 July 1989; accepted & revisedform 4 April 1990)
Abstract--Research has shown that aerobic exercise is effective in alleviating depression. However, the contention that aerobic exercise similarly has an enduring beneficial psychological effect on the mood of normal, non-depressed individuals has not been verified. Research examining the effects of exercise on normal mood has yielded inconsistent findings, due in part to methodological shortcomings. The present study attempted to rectify these methodological difficulties and evaluated the effect of 13 weeks of aerobic exercise on the mood of normal, non-depressed men and women. Groups intended to be non-aerobic and waiting list controls were included in the design, as were a stratified random sampling procedure, measurement of physical fitness, and a seven-day pre/post-program assessment period for both positive and negative mood. Results indicated that, although subjects demonstrated significant improvement in physical fitness, there were no significant changes in either positive or negative mood. Thus, in contrast to effects with clinical depressives, exercise does not appear to have any long-term beneficial effect on the mood of non-depressed individuals selected from a normal, i.e. non-clinical, population.
INTRODUCTION RESEARCH d e m o n s t r a t i n g the beneficial effects o f a e r o b i c exercise on physical health [1, 2] has led to m e n t a l health applications. Such research has clearly indicated that a e r o b i c exercise can reduce the s y m p t o m s o f depression [3]. Results with depression have been interpreted to suggest that exercise will also e n h a n c e the m o o d a n d vigor o f n o r m a l , n o n - d e p r e s s e d individuals. H o w e v e r , the literature e x a m i n i n g this h y p o t h esis is s o m e w h a t difficult to interpret given inconsistent findings, due in p a r t to m e t h o d o l o g i c a l s h o r t c o m i n g s . T h e r e is currently little definitive scientific evidence to s u p p o r t or refute the c o n t e n t i o n that a e r o b i c exercise has e n d u r i n g beneficial p s y c h o l o g i c a l effects on the m o o d o f n o r m a l , n o n - d e p r e s s e d individuals. Earlier studies 1970-1982
W i t h some exception [4, 5], much o f the p r e l i m i n a r y research that e x a m i n e d the effects o f exercise on n o r m a l m o o d was c h a r a c t e r i z e d by significant m e t h o d o l o g i c a l p r o b l e m s that preclude i n t e r p r e t a t i o n o f findings. Investigators: (a) allowed subjects to self-select whether they w o u l d a t t e n d exercise or c o n t r o l p r o g r a m s [6, 7]; (b) used c o r r e l a t i o n a l designs that precluded causal statements regarding m o o d a n d exercise [8-1 I]; (c) simply c o m p a r e d the m o o d o f people who exercised regularly with those w h o did not, w i t h o u t c o n s i d e r a t i o n o f the biased n a t u r e o f such g r o u p s [10, 12]; (d) e m p l o y e d g r o u p designs with i n a d e q u a t e o r no c o n t r o l s [9, 13, 6, 7); (e) c o n d u c t e d exercise p r o g r a m s t o o short in d u r a t i o n to optimize physical fitness changes [7]; a n d / o r (f) failed to either m e a s u r e or r e p o r t changes in physical fitness [6, 7]. U n f o r t u n a t e l y , the two well designed studies [4, 5] excluded w o m e n a n d were Albert Einstein College of Medicine, Yeshiva University, New York, U.S.A. Mailing Address: Shelley S. Lennox, Ph.D., Department of Psychiatry, Albert Einstein College of Medicine, Yeshiva University, 2527 Glebe Avenue, Bronx, NY 10461 U.S.A. *Department of Psychology, State University of New York at Stony Brook, Stony Brook, New York, U.S.A. 629
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conducted immediately post-myocardial infarction, thus limiting the generalizability of findings to male cardiac patients. Methodological problems were also accompanied by inconsistencies in findings. For instance, some studies reported either superior mood in regular exercisers or mood enhancement following an aerobic exercise program [6, 10, 14], while others failed to observe effects [7, 8]. Moreover, some investigators observed that, with ostensibly normal samples, i.e. individuals not selected from a psychiatric population, beneficial psychological change occurred primarily for those with the worst psychological and/or physical status (see Ref. 15 for brief review). However, there is some indication that these individuals were, indeed, clinically depressed and, therefore, mistakenly included in the 'normal' samples. Recent studies 1983 to present
Recent years have witnessed the emergence of a number of studies that have attempted to rectify many of the methodological problems mentioned. With some exception [16]. investigations conducted over the past seven years have incorporated randomized trials and physical fitness assessment in their designs. Inconsistent findings, however, have still been observed. Although the reason(s) for these discrepancies is not immediately apparent, the studies do vary on several potentially relevant variables, one of which is the subject sample assessed. Although all the studies evaluated for the present investigation purportedly selected participants from the 'general' population, two required that candidates demonstrate clinically significant anxiety upon admission [17, 18]. Obviously, the positive mood findings with these samples cannot be used to support the hypothesis that exercise induces mood improvement in psychologically 'normal' individuals. The remaining studies found in the literature all sampled from non-clinical populations, however, three of them excluded women [19 21]. Findings observed in these studies were mixed, with three of them reporting no reduction in depression [21-23], one reporting inconsistent effects [19], and another reporting improvement in subjective well being [20]. The findings of Hughes, Casal and Leon [21], however, are particularly questionable as their training program appears to have produced minimal change in functional capacity (duration of time on treadmill (rain.) pre-program = 10.9, post-program = 11.1). In addition to sample differences, recent studies also vary in the degree to which they control extraneous variables. For example, excluding the two investigations that evaluated individuals with clinical disorder [17, 18], one study did not control for the passage of time [19], others failed to control for involvement in non-aerobic activity [21-23], while another did not control for either of these factors [20]. Interpretive difficulties also arise from assessment procedures that are neither uniform nor adequately described. In many instances, investigators have not indicated when, in relation to the exercise session, post-program mood measures were completed [19-21]. If measurement followed immediately upon the exercise session (even if it was not a state measure), it would have been biased toward reflecting the short-term and transitory effects of exercise. As the research question of interest is whether regular exercise produces persistent (not transitory) mood change, measurement of mood distant in time from the episode of exercise is essential
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Obviously, despite improvement in the methodological rigor of recent studies investigating the effect of regular aerobic exercise on the mood of normal individuals, interpretive difficulties remain. Differences in samples and control of extraneous but relevant variables, as well as variability in assessment procedures, all contribute to the problem. In addition, although recent exceptions hopefully represent a trend [20, 22], investigators have typically used dependent measures that emphasize evaluation of changes in negative mood (primarily depression and anxiety) [19, 21]. Since the mood of 'normals' is generally defined by the absence of significant depression or anxiety, scales based on the measurement of negative mood alone leave little room for non-depressed individuals to report improvement since a ceiling effect is encountered. Use of scales designed to measure 'positive mood' is essential when evaluating the effects of exercise on the mood of normal individuals.
The present study The purpose of the present investigation was to employ a research design and methodology that would help rectify some of the methodological difficulties cited, and to evaluate the effect of regular aerobic exercise on the mood of non-depressed individuals. To achieve this objective, we evaluated the effects of a substantial period of exercise training (i.e. 13 weeks) on the mood of physically and psychologically healthy adult volunteers. To control for unmanipulated yet outcome-related variables, a waiting-list group and a group designed to engage in non-aerobic exercise were also included in the study. Subjects were assigned to the three experimental conditions by means of a stratified random sampling procedure. To verify the aerobic manipulation, physical' fitness was assessed before and after the 13-week program. To increase reliability and the probability of evaluating relatively persistent mood effects, post-program mood was assessed for seven days, well after the transitory effects of exercise has subsided. Finally, we used measures of positive as well as negative mood, and included both men and women in the study, enabling the evaluation of sex effects. METHOD
Sul~jects Seventy employees of the Veterans Administration Medical Center in Northport, LI, volunteered to participate in an exercise program ostensibly conducted for the purpose of reducing the risk of heart attack. Subjects were assigned to experimental conditions using a stratified random sampling procedure. They were first matched on sex, positive and negative mood (as assessed by the Multiple Adjective Checklist, M A C L , [24], and the Depression Adjective Checklist, DACL, [25]), and physical fitness (funtional capacity), then randomly assigned to the walk-jog (W J), volleyball/weight lifting (VB), or waiting-list control groups. Forty-seven subjects, 15 each in VB and WJ (both containing nine females and six males) and 17 in the control group (11 females, six males), completed the study, with 23 of the original volunteers (10 VB, nine W J, four controls) terminating participation in the program. The most c o m m o n reason for termination was work schedule conflict. Comparison of subjects who completed the program with those who did not revealed no differences in age, education, marital status, or sex. There were no significant differences in the percentage of drop-outs a m o n g the three groups. The mean ages of male and female participants were 43 and 47 yr, respectively. With the exception of one S (who had undergone coronary bypass surgery three years prior to the study), no subject had experienced a myocardial infarction or reported a history of heart disease. All were negative for ischemia on the stress test. All participants denied involvement in regular exercise (of at least 15 rain duration three times per week) and scored below 10 on the Beck Depression Inventory-short form (BDI), [26], the criterion used to eliminate prospective participants with clinically significant depression.
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~leasures Physicalfimess assessment. The primary measure of physical fitness was functional capacity, defined as the number of minutes the subject walked or walked/ran from start to voluntary termination of exercise (voluntary maximum) on the treadmill stress test. Performance was evaluated with the Bruce Protocol [27] (Burdiek Stress Test Machine, System IIl Channel EXTOT, Three Channel Electrocardiograph, EK670). Sel/2report inventories o[" depression and mood. The Beck Depression Inventory-short form (BDI) was used to evaluate the presence of clinically significant depression. With well documented psychometric properties, the BDI consists of 13 multiple-choice items and yields a score ranging from 0 to 39, with higher numbers reflecting greater depression. The Depression Adjective Checklist (DACL) consists of 26 adjectives that assess depressed mood. Scores range from 0 to 26, with higher values reflecting more dysphoria. The Mood Adjective Checklist (MACE) is a 33-adjective checklist that measures positive and negative mood states. The seven factors comprising these mood states include sadness, anxiety, aggression, fatigue, surgency, vigor and elation, The first four factors represent negative affects and were combined to form a composite measure of dysphoria, while the last three represent positive affects, and were combined into a measure of euphoria.
Procedure Upon entry into the study, subjects underwent a stress test to voluntary maximum, were administered the BDI, MACL and D A C E and then assigned to the WJ, VB, or waiting-list group. The MACL and DACE were completed at the end of the day for seven days prior to commencement of exercise. The mean of the seven daily scores served as the dependent measure of pre-treatment mood. Subjects assigned to the exercise conditions (WJ or VB) met for 50-450 min three times per week for 13 weeks, and two instructors led each group. Exercise groups started with 5-10 rain of stretching, then proceeded with assigned activity. Subjects in the WJ (aerobic) group utilized individualized exercise prescriptions that attempted to have S walk or jog at 70 80% of heart rate capacity (as determined on ttle pre-program stress test) and expend approximately 300 calories per session. This was accomplished by first computing 56 70% of the maximum oxygen consumption (equal to 70 80% of maximum heart rate) estimate derived from the stress test, and then converting this to a measure of speed. Calorie requirements per minute, based upon body weight and speed of walking or jogging, were then computed and divided by 300 to determine the duration of exercise required to consume 300 calories [28, 29]. A quarter-mile cement walkway around a courtyard served as the main track. Subjects in the VB group (designed to function as the non-aerobic exercise condition) engaged in 10 15min of weight lifting and calisthenics, followed by 30 35 rain of volleyball. Weight lifting and calisthenics were selected as activities because of their known failure to produce aerobic training effects [30]. Although power or competitive volleyball will produce cardiovascular benefit, the recreational nature of the game planned for our inexperienced subjects was not expected to result in significant changes in aerobic capacity [31]. To increase the similarity of WJ and VB members' experience of mastery and accomplishment, the weight lifting and calisthenics component of the program included progressive increments in difficulty, with modification of individualized regimens determined jointly by subject and group leader. The waiting-list control subjects were instructed to refrain from involvement in regular exercise for the 13-week study period, and were informed that an exercise program would become available to them at that time. Within a week of termination of the exercise progranr, all Ss again underwent a stress test to voluntary maximum, and completed the MACL and DACL at the end of each day for seven days.
RESULTS
Physical fitness A n a n a l y s i s o f v a r i a n c e ( A N O V A ) w a s u s e d to a s s e s s t h e effects o f g r o u p VB, c o n t r o l s ) , sex ( M , F ) a n d t i m e ( p r e , p o s t t r e a t m e n t ) o n f u n c t i o n a l c a p a c i t y o n t r e a d m i l l ) . T h e A N O V A y i e l d e d s i g n i f i c a n t m a i n effects o f sex ( F ( 1 , 3 8 ) = p < 0.013) a n d t i m e ( F ( 2 , 3 8 ) = 24.36, p < 0.001), a n d a s i g n i f i c a n t i n t e r a c t i o n
( W J, (time 6.71, effect
o f g r o u p a n d t i m e ( F ( 2 , 3 8 ) = 6.08, p < 0.05). T h e m a i n effect o f sex i n d i c a t e d t h a t m e n d e m o n s t r a t e d g r e a t e r f u n c t i o n a l c a p a c i t y t h a n w o m e n . T h e m a i n effect o f t i m e is b e s t u n d e r s t o o d in t e r m s o f t h e g r o u p x t i m e i n t e r a c t i o n . E v a l u a t i o n o f t h e m e a n s a s s o c i a t e d w i t h this i n t e r a c t i o n (see T a b l e I)
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TABLE I.-- MEANS AND STANDARD DEVIATIONS OF PRE- AND POST-TREATMENT FUNCTIONAL CAPACITY SCORES FOR SUBJECTS IN THE AEROBIC ( W J), NON-AEROBIC (VB) AND NO-EXERCISE CONTROL GROUPS
Functional capacity Type of exercise Aerobic (WJ) Non-aerobic (BV) No-exercise (Control)
n 15 15 17
Pre-treatment Post-treatment 9.79 (2.31) II.85 (2.24) 10.01 (2.14) 11.50 (2.19) 10.23 (1.83) 10.45 (2.14)
indicated that, while there were no significant differences in pre-treatment functional capacity among the three groups, significant improvement was observed post-treatment in the two exercise groups, both of which exhibited significant increases relative to controls (VB vs controls: F(1,24) = 5.6, p < 0.025; WJ vs controls: F(1,25) = 16.4, p < 0.001). Additionally, there was no significant difference in improvement between the WJ and VB groups, and no significant pre-post improvement in the no treatment control group. Positive and negative m o o d
Similar to functional capacity, each of the three mood variables (i.e. scores on the D A C L and the two subscales of the MACL) was evaluated with a group (W J, VB, control) by sex (M, F) by time (pre-post treatment) A N O V A with repeated measures on time. None of these analyses yielded any significant effects. Thus, there were no significant differences among groups, between sexes, or across time in (a) depressed mood or depressive symptomatology as measured by the D A C L or M A C L (dysphoria subscale), or (b) positive mood as measured by the M A C L (euphoria subscale). DISCUSSION The present study evaluated the effects of regular aerobic exercise on normal mood through an experimental design that attempted to eliminate many of the methodological inadequacies precluding clear interpretation of previous research findings. Current findings indicated that, although subjects demonstrated significant improvement in physical fitness, they did not evidence significant improvement in positive or negative mood. Thus, in contrast with clinical depressives, whose depression improves following aerobic exercise training, normal adults do not appear to experience such beneficial m o o d changes. The current findings, inconsistent with those observed by Brown et al. and Goldwater and Collis [6, 20], support the observations of King et al. [22] and Moses et al. [23], who found no reduction in depression following aerobic training. Morgan et al. [7], Folkins et al. [13], and Simons and Birkimer [16] similarly found no improvement in depression among non-depressed Ss, although they did observe such training-induced change in depressed individuals. It is of interest to note that the VB program, designed to function as the non-aerobic activity (and intended to control for effects correlated with a supervised group exercise program but not attributable to the aerobic nature of such exercise), produced increases in functional capacity similar in magnitude to those of
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walk-jogging. This finding indicates that we were not successful in producing a non-aerobic condition and, in effect, evaluated the efficacy of two different aerobic programs of varying intensity. (The group mean exercise heart rate as computed from the mean pulse value of each subject across the middle five weeks of the program was 65% and 83% of maximum for the VB and WJ groups, respectively.) It also suggests that, for sedentary individuals, regular involvement in activity that is generally not classified as "aerobic' can produce cardiovascular fitness improvement typically associated with activities so classified. Similar findings have been observed elsewhere [28]. It is possible that a more rigorous walk~og program, or a study period of longer duration, would have distinguished the groups. Although the present authors' failure to effectively include a non-aerobic group compromises the methodological rigor with which the study was conducted, several factors combine to support the validity of findings with regard to the hypothesis under consideration. First and foremost, the magnitude of increase in functional capacity for subjects in the exercise conditions was similar to that observed in other studies, even those of longer duration [2, 32]. Thus, an aerobic training effect was produced. Moreover, in the presence of this physical fitness training effect, mood change was not produced. The failure to include a non-aerobic group does not question the validity of this finding. Interpretive difficulties would have resulted only if mood changes had been observed. Under this circumstance, it would have been impossible to sort out the independent effect of the aerobic variable. The present study can also be faulted tbr its failure to evaluate subject expectancies. Given the potential relevance of this variable to mood outcome, its measurement should be included in all future research. The failure of the present study to observe increases in positive mood obviously needs to be reconciled with frequent reports of a euphoric experience after exercise. Given the latter, present findings appear to counter subjective reality. However, the two observations are not necessarily incompatible as they may, in fact, refer to different effects. Anecdotal reports of euphoria or exhilaration frequently refer to acute mood effects, i.e. those occurring during or immediately tbllowing an exercise session [33 36], whereas the current study evaluated the presence of more stable or persistent mood changes as a result of engagement in regular exercise over a sustained period of time. The latter is of much greater significance. Taken together, the findings seem to indicate that a bout of exercise may produce short-term improvement in the m o o d of normal individuals, but does not result in any persistent mood change. Moreover, in contrast to depressives, non-depressed individuals do not appear to experience any stable beneficial m o o d changes following participation in regular exercise over a sustained period of time. As indicated in the Introduction, a limiting factor of some previous studies was their failure to either measure, report, or possibly achieve, physical fitness effects [6, 7]. Since the efficacy of any aerobic exercise program is determined by measurable cardiovascular changes, evidence of physical fitness benefit is essential. Findings of the current study provide this evidence, with walk~oggers demonstrating significant increases in functional capacity. This suggests that the failure to observe mood changes was not the result of an inadequate training program. In conclusion, the literature suggests that exercise is at least a partial remedy for dysphoric mood in depressed individuals and may offer short-term elevations in the
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mood of normal, non-depressed individuals. The present study, however, indicates that the effects of exercise do not appear to have any long term beneficial effect on t h e m o o d o f n o r m a l i n d i v i d u a l s , e i t h e r t h r o u g h (a) t h e a l l e v i a t i o n o f d y s p h o r i a negative mood, or (b) enhancement of positive mood.
or
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