The effect of moderate exercise on mood in mildly hypertensive volunteers: A randomized controlled trial

Journal of Psychosomatw Research, Vol. 40, No. 6, pp. 637-642, 1996 Published by Elsevier Science Inc. All rights reserved. 0022-3999/96

ELSEVIER

0022-3999(95)00643-5

THE EFFECT OF MODERATE EXERCISE ON MOOD IN MILDLY HYPERTENSIVE VOLUNTEERS: A RANDOMIZED CONTROLLED TRIAL J O S E P H I N E M. S T A N T O N a n d B R U C E A R R O L L (Received 18 April 1994; accepted 12 October 1995) Abstract--This study reports an investigation of the effect of participating in moderate exercise (three 40-min sessions of brisk walking a week for 6 months) on mood state in 177 sedentary, mildly hypertensive volunteers. Mood was assessed by the Profile of Mood States, Bipolar Form (POMS-BI), and no significant differences were found between control and exercise groups. The intervention group increased its exercise output more than the control group, but there was also a significant increase in exercise done by the control group. We conclude that exercise has no major effect on mood in hypertensive volunteers. Keywords:

Exercise; Mood; Anxiety; POMS-BI.

INTRODUCTION T h e r e has b e e n c o n s i d e r a b l e i n v e s t i g a t i o n into t h e r e l a t i o n s h i p between exercise a n d m o o d . M a n y c r o s s - s e c t i o n a l a n d q u a s i - e x p e r i m e n t a l studies h a v e s h o w n positive associations b e t w e e n level o f p h y s i c a l activity a n d g e n e r a l well-being, lower levels o f anxiety a n d d e p r e s s i o n , a n d positive m o o d (1-7). E x p e r i m e n t a l studies have d e m o n s t r a t e d s u p p o r t for a m o o d - e n h a n c i n g effect o f exercise in d e p r e s s e d , anxious, o r stressed subjects (8-13) a n d a positive acute effect o f a single b o u t o f exercise o n a n x i e t y (14-16). Results f r o m r a n d o m i z e d c o n t r o l l e d trials that l o o k e d at w h e t h e r a s u s t a i n e d p e r i o d o f r e g u l a r exercise i m p r o v e s the m o o d o f n o r m a l subjects have been mixed. Small s a m p l e sizes a n d d r o p - o u t rates in excess o f 30°70 have l i m i t e d the p o w e r o f m o s t o f t h e studies. C r a m e r et al. [17] f o u n d s u s t a i n e d significant i m p r o v e m e n t o n the G e n e r a l W e l l Being Schedule, b u t n o t on o t h e r m o o d scales. Several studies have s h o w n c h a n g e in subjects' a n x i e t y o r in their p e r c e p t i o n o f themselves a n d their stress (18-23). M a n y s h o w e d no significant effects (24-27). This p a p e r r e p o r t s an i n v e s t i g a t i o n o f the effect o f r e g u l a r brisk w a l k i n g o n m o o d states. This i n v e s t i g a t i o n was p a r t o f a large, c o m m u n i t y - b a s e d r a n d o m i z e d trial that assessed the effect o f salt i n t a k e a n d exercise o n b l o o d pressure.

*Address correspondence to: Josephine M. Stanton, Kahikatea, Mason Clinic, P. O. Box 19-986, Avondale, Auckland, New Zealand. A report of findings from a study done in the Department of General Practice, University of Auckland, Private Bag 92019, Auckland 1, New Zealand. 637

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METHODS Subjects Subjects were recruited through their general practitioners and through advertisements in community newspapers. The inclusion criteria were essential hypertension, aged between 20 and 69 inclusive, a sedentary lifestyle, and being managed by a primary care doctor. Exclusion criteria were symptomatic coronary heart disease, immobility that restricted walking, current diastolic blood pressure greater than 105 mmHg or a systolic blood pressure greater than 180 mmHg, and currently performing regular moderate activity. This excluded persons who were involved in more than 2 hours of moderate leisure time activity per week other than housework or gardening (brisk walking is an example of moderate activity while running is a vigorous activity). Of the initial 208 participants, 181 (87°70) completed the study. These were 86 women and 95 men. Average age o f the sample was 55 years with a range of 26 to 71 and a standard deviation of 9.4 years. POMS-BI scores were available for 177 of these, that is 85070 o f the original participants (90 in the exercise group and 87 in the control group).

Outcome measures Mood. The measure used to evaluate the effect of exercise on mood was the bipolar form of the Profile of Mood States (POMS-BI) [28]. This is a self-report questionnaire developed from the unipolar form [29]. It consists of 72 adjectives, each of which is rated on a 4 point scale from 0 much unlike this to 3 much like this. Subjects can be asked to rate how they feel "right now" or how they have felt over the past week. In this study subjects were asked to rate how they felt "over the past week." The scale was constructed to measure 6 bipolar mood states: composed-anxious, agreeable-hostile, elated-depressed, confident-unsure, energetic-tired, clearheaded-confused. Each scale has 12 items with a potential range o f 0 to 36. Higher scores represent more positive mood. The POMS-BI has been tested in normal adults, psychiatric outpatients, university students, and high school students. Test-retest reliability of the scales in university students ranged from 0.33 to 0.72; most were between 0.54 and 0.60. Psychometric properties of the POMS-BI and studies supporting its construct validity are presented in the POMS-BI manual [28]. Physical activity. The Auckland Heart Study Exercise Questionnaire (AHSEQ) was used to measure levels of physical activity. This is a 3-month questionnaire involving recall of physical activity. The a format is similar to that used in the Stanford Five City Project [30]. Questions were asked about hours per day spent in sleep or rest and in moderate or vigorous activity. Light activity was calculated as the remaining hours in the 24-hr day. This approach is most efficient because light activities, which are the most frequently performed, do not need to be recorded. The questionnaire has been validated against a daily diary [31]. Correlations between total exercise as reported on the questionnaire and as reported in the diary were 0.86 (Spearman's correlation) and 0.91 (Pearson correlation). Reliability was not directly measured. Other. Plasma high density lipoprotein (HDL) was determined from a non fasting venous sample. Body weight was measured by a standard balance scale, and blood pressure was measured blindly using Hawksley random zero sphygmomanometers. Design The study used a factorial, randomized control design that enabled an analysis comparing the effect of exercise separately from that of salt restriction. Sedentary adult volunteers were randomly assigned to an exercise or control group. Participants in the exercise group were advised to walk briskly for 40 minutes 3 times per week over a 6-month period. An appropriate build-up period o f exercise for participants who were initially inactive was determined by their own doctor. At the baseline assessment and at the 6-month follow up POMS-BI and the exercise questionnaire were administered, blood samples were taken, and patients were weighed. All participants kept a weekly diary noting health problems experienced during the week as well as compliance with medication. In addition, the exercise subjects recorded compliance with exercise. Statistical analysis was done using JMP version 2.05, a statistical package for Macintosh computers from the SAS Institute (Cary, NC).

RESULTS The mean POMS-BI scores of both groups generally improved over the period of the study. There was no significant difference between the groups on any of the s u b s c a l e s ( T a b l e I). C o n t r o l l i n g f o r t h e b a s e l i n e s c o r e s d i d n o t a l t e r t h e f i n d i n g s .

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Table I . - Baseline POMS-BI scores and change at 6 months for exercise and control groups. Subscale Composed/anxious exercise control Agreeable/hostile exercise control Elated/depressed exercise control Confident/unsure exercise control Energetic/tired exercise control Clear headed/confused exercise control

Baseline

6 months

P

24.2 24.1

24.9 24.6

0.71

27.0 26.2

27.1 26.8

0.71

23.4 23.9

24.1 23.6

0.60

23.2 23.1

24.4 23.6

0.35

21.6 21.8

23.2 22.1

0.25

28.2 28.40

28.1 27.7

0.64

n = 177; exercise group n = 90; control group n = 87; the range of standard errors is 0.5 to 0.7 for the baseline scores and 0.6 to 0.7 for the exit interviews. All analyses t test; degrees of freedom 175.

All participants reported an increase in exercise as measured by the A H S E Q . There was a significant difference in the a m o u n t of moderate and total exercise activity reported between the groups at 6 months (Table II). Both exercise and control groups reported significant increases in moderate and total activity from the baseline to the exit interview. H D L levels rose by 5% in the exercise group and d r o p p e d by 4% in the control group. This difference was statistically significant (p = 0.004). Systolic blood pressure fell by 8.2 m m H g in the control group and by 7.2 m m H g in the exercise group. Diastolic b l o o d pressure fell by 3.1 m m H g in the control group and by 2.1 m m H g in the exercise group. The control group lost 0.63 kg and the exercise group 0.7 kg body weight. The differences between groups in these changes in blood pressure and weight were nonsignificant.

DISCUSSION No significant effect of exercise on m o o d state was found. A n y effect may have been minimized by the increase in exercise in the control group. This increase may have been influenced by the change in seasons over the duration of the study. The baseline assessment t o o k place in the winter and the 6-month assessment at the end of summer when it would be expected that participants would increase their physical activity. Participants m a y have been stimulated to increase their exercise by being in a study and completing a baseline exercise questionnaire. As most previous studies have not attempted to measure exercise done by the control group, it is not known whether a similar increase in exercise in control groups may have contributed towards masking an effect of exercise on n o r m a l mood. Most previous

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J. M. STANTON and B. ARROLL Table I I . - Moderate and total activity values at baseline, 3-month, and 6-month assessment in kcal/kg/day (SE) (exercise n = 90 and control n = 87) Intervention Exercise Moderate Total Control Moderate Total

Baseline

6 Month

3.7 (0.7) 34.6 (0.5)

11.4 (1.2) t,5 39.4 (0.8) 2.6

2.9 (0.7) 34.3 (0.5)

7.0 (1.2) 3 37.0 (0.8) 4

Exercise versus control at 6 months (moderate activity) p = 0.012 (ANOVA). Controlling for baseline level of physical activity, p = 0.01. 2 Exercise versus control at 6 months (total activity) p = 0.03 (ANOVA). Controlling for baseline level of activity, p = 0.02. 3Six months versus baseline within control group (moderate activity) p = 0.0001 (paired t test). 4 Six months versus baseline within control group (total activity) p = 0.0001 (paired t test). 5 Six months versus baseline within exercise group (moderate activity)p = 0.0001 (paired t test). 6 Six months versus baseline within exercise group (total activity) p = 0.0001 (paired t test).

studies have m e a s u r e d fitness a n d f o u n d significant differences between exercise a n d c o n t r o l g r o u p s . In the l i t e r a t u r e on the benefits o f exercise for general health there is a t r e n d f o r increase in t o t a l energy e x p e n d i t u r e to be seen as a m o r e useful o u t c o m e t h a n increase in fitness [32-33]. In a n o n e x p e r i m e n t a l s t u d y t h a t l o o k e d at the p s y c h o logical benefits f r o m exercise, T h i r l a w a y a n d B e n t o n [7] f o u n d t h a t it was p a r t i c i p a t i o n in p h y s i c a l activity, r a t h e r t h a n c a r d i o v a s c u l a r fitness t h a t was the f a c t o r a s s o c i a t e d with better m e n t a l h e a l t h a n d m o o d . T h e m a j o r strengths o f this s t u d y are its large size, relatively low d r o p - o u t rate, a n d use o f a widely used m e a s u r e o f m o o d states d e v e l o p e d for use in n o r m a l as well as p s y c h i a t r i c a l l y ill subjects. It is a c o m m u n i t y - b a s e d s t u d y o f t h e effect o f an i n s t r u c t i o n to exercise, a n i n t e r v e n t i o n which is easily replicable in clinical practice. H o w e v e r , t h e use o f s u b j e c t s with essential h y p e r t e n s i o n in the s t u d y m a y limit its g e n e r a l i z a b i l i t y . It is also possible t h a t some a n t i h y p e r t e n s i v e m e d i c a t i o n m a y b l u n t the beneficial effect o f exercise. It is p o s s i b l e t h a t the P O M S - B I was not a responsive e n o u g h i n s t r u m e n t to pick u p changes in m o o d as a result o f exercise. S o m e n o n e x p e r i m e n t a l studies have d e m o n s t r a t e d significant changes in s u b j e c t s ' scores on the u n i p o l a r Profile Of M o o d States [29] ( P O M S ) f o l l o w i n g exercise [5, 34]. H o w e v e r , their subjects m a y have been a s k e d to rate h o w t h e y felt "right n o w " r a t h e r t h a n " o v e r the last w e e k , " which m a y have led to m o r e responsiveness in t h e m e a s u r e . W h i l e significant beneficial effects on a n x i e t y h a v e been f o u n d , n o n e o f the previous r a n d o m i z e d trials has d e m o n s t r a t e d significant effects o f s u s t a i n e d exercise on general m o o d scales. A s m a n y o f the studies were small a n d h a d large d r o p - o u t rates, this

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641

m a y have reflected a l a c k o f p o w e r . King et al. [20] h a d relatively large g r o u p s (60 in each o f exercise g r o u p a n d 60 c o n t r o l s ) with g o o d r e t e n t i o n o f subjects. T h e y d e v e l o p e d a 14-item r a t i n g scale to m e a s u r e p s y c h o l o g i c a l o u t c o m e s . N o significant differences were f o u n d o n the items relating t o d e p r e s s i o n o r d y s p h o r i c m o o d . In a n o t h e r r a n d o m i z e d c o n t r o l l e d trial, King et al. [21] i n v e s t i g a t e d the effect o f 1 y e a r o f exercise in 357 subjects. T h e y f o u n d benefits in t e r m s o f a n x i e t y a n d perceived stress a n d well-being. T h e m o o d scale t h e y used was the Beck D e p r e s s i o n I n v e n t o r y (BDI) [35], a n d t h e y f o u n d no significant differences. This negative result in such a large, well-designed s t u d y is clearly i m p o r t a n t . H o w e v e r , the B D I m a y n o t be p a r t i c u larly r e s p o n s i v e to a c h a n g e in m o o d in n o n d e p r e s s e d subjects. T h e limited benefits o f s u s t a i n e d exercise d e m o n s t r a t e d b y r a n d o m i z e d c o n t r o l l e d trials c o n t r a s t with the s t r o n g r e l a t i o n s h i p f o u n d between exercise a n d m o o d in crosssectional (i.e., n o t p r o s p e c t i v e ) studies. T h e y also c o n t r a s t with benefits a s s o c i a t e d with exercise in p r o s p e c t i v e q u a s i - e x p e r i m e n t a l studies in which subjects self-select into exercise g r o u p s . This is in spite o f the fact t h a t m o s t o f the e x p e r i m e n t a l studies d i d n o t have a p l a c e b o c o n d i t i o n to c o n t r o l for a n y nonspecific effect o f being i n v o l v e d in a t r e a t m e n t c o n d i t i o n . This m i g h t be an e x a m p l e o f a p h e n o m e n o n seen in m a n y areas o f research, t h a t the m a g n i t u d e o f an effect tends to be inversely r e l a t e d to the rigor o f the m e t h o d o l o g y used to s t u d y it [36]. A l t e r n a t i v e l y , a n i n t e r a c t i o n between the choice to exercise a n d the beneficial effects o f exercise on m o o d c o u l d also explain the d i s c r e p a n c y . It m a y b e t h a t at t h e p o i n t at which s o m e o n e chooses to exercise, their m o o d is susceptible t o i m p r o v e m e n t a n d t h u s the exercise has a beneficial effect o n their m o o d . This susceptibility to i m p r o v e m e n t m a y not be present w h e n they are r a n d o m i z e d into an exercise g r o u p . In c o n c l u s i o n , this s t u d y f u r t h e r u n d e r m i n e s t h e h y p o t h e s i s t h a t increase in physical exercise will lead to a s u s t a i n e d i m p r o v e m e n t in m o o d in t h e general p o p u l a t i o n .

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