HEALTH PSYCHOLOGY, 70(6), 384-391 Copyright © 1991, Lawrence Erlbaum Associates, Inc.
Stress Reactivity and Exercise Training in Premenopausal and Postmenopausal Women James A. Blumenthal Department of Psychiatry Duke University Medical Center
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Mats Fredrikson Department of Psychiatry and Psychology Karolinska Institute and Stockholm University
Karen A. Matthews Department of Psychiatry University of Pittsburgh School of Medicine
Cynthia M. Kuhn Department of Pharmacology Duke University Medical Center
Susan Schniebolk Department of Psychiatry Duke University Medical Center
Deborah German Department of Medicine Vanderbilt University
Nader Rifai Department of Laboratory Medicine Children's National Medical Center
John Steege Department of Obstetrics and Gynecology Duke University Medical Center
Judith Rodin Yale University Examined the influence of ovarian function on psychophysiological stress responses and determined if aerobic exercise reduced stress reactivity. Fifty premenopausal and postmenopausal women initially were subjected to a public speaking task and an ice-on-the-forehead procedure, during which time their blood pressure and heart rate were monitored and continuous blood samples were obtained. Subjects also underwent aerobic fitness evaluations with a maximum-exercise treadmill test. Subjects were then randomly assigned to a 12-week exercise program of either aerobic exercise (e.g., walking and jogging at a prescribed exercise intensity) or non-aerobic strength and flexibility training and were then reevaluated. Results indicated that postmenopausal women exhibited lower resting epinephrine levels but greater epinephrine reactivity to the speaking task compared to the premenopausal women. There were no differences between premenopausal and postmenopausal women with respect to cardiovascular or catecholamine responses during the cold challenge. Premenopausal and postmenopausal women also achieved comparable improvements in aerobic fitness. However, results of the mental stress testing were complex and provided only partial support for the role of aerobic exercise in reducing stress responses. Key words: aerobic exercise, weight training, reproductive hormones, physiological reactivity Coronary heart disease (CHD) is a significant health problem for women as well as for men. In most industrialized coun-
Requests for reprints should be sent to James A. Blumenthal, Department of Psychiatry, Duke University Medical Center, Box 3119, Durham, NC 27710.
tries, CHD accounts for about one third of all deaths in women (World Health Organization, 1980). The traditional risk factors —hypertension, hyperlipidemia, and cigarette smoking —appear to be at least as important for women as they are for men. Other factors also are likely, however, and investigators have focused on biobehavioral influences that may be relevant for the development of CHD in women.
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STRESS REACTIVITY, EXERCISE, MENOPAUSE
This study examined two related issues. First, research has shown that exaggerated physiological responses to behavioral stimuli may contribute to CHD (Krantz & Manuck, 1984; Matthews et al., 1986). Because menopause is not only associated with increased risk of CHD but is also accompanied by significant hormonal changes, the influence of ovarian function on psychophysiological reactivity to stress has received increased attention (Manuck & Polefrone, 1987). For example, studies have indicated that, during various challenging stressors, women compared to men tend to exhibit greater heart rate (HR) responsivity but that women have smaller blood pressure (BP) and epinephrine stress responses compared to men (Collins & Frankenhaueser, 1978; Frankenhaueser, 1983; Frankenhaueser, Dunne, & Lundberg, 1976; Frankenhaueser, Lundberg, & Forsman, 1980; Johansson, 1972; Johansson & Post, 1973; Lundberg, 1983; Matthews & Stoney, 1988; Shapiro, 1961; Stoney, Davis, & Matthews, 1987). Studies of hormonal influences on cardiovascular stress reactivity have also compared premenopausal and postmenopausal women. Saab, Matthews, Stoney, and McDonald (1989) showed that postmenopausal women exhibited greater increases in HR, systolic BP (SBP), and epinephrine than did premenopausal women during a public speaking task; however, there were no BP or catecholamine differences among premenopausal and postmenopausal women during several other tasks including mental arithmetic, mirror-image tracing, and postural tilt. In the present study, we compared premenopausal and postmenopausal women's cardiovascular and neuroendocrine responses to two different behavioral stressors —a public speaking task and a cold challenge. We hypothesized that postmenopausal women would be more reactive than premenopausal women on the speech task but not during the cold task. A second issue of interest concerned the physiologic effects of exercise. Previous studies, mostly of men, have reported that aerobic exercise training may attenuate cardiovascular and neuroendocrine responses to stress. Cross-sectional comparisons of fit and unfit individuals have generally shown that fit subjects exhibit reduced cardiovascular stress responses compared to unfit subjects (Crews & Landers, 1987). However, few studies of adult women have been reported. Moreover, randomized longitudinal studies of men have yielded inconsistent findings. To our knowledge, only three studies have shown that aerobic exercise training reduces cardiovascular stress responses (Blumenthal, Emery et al., 1988; Blumenthal et al., 1990; Sherwood, Light, & Blumenthal, 1989). Other studies have been either equivocal (Sinyor, Golden, Steinert, & Seraganian, 1986) or negative (Roskies et al., 1986; Sinyor, Peronnet, Brisson, & Seraganian, 1987; Steptoe, Moses, Mathews, & Edwards, 1990). The present investigation examined the changes in aerobic capacity in a group of middle-aged women and assessed the effects of aerobic fitness on cardiovascular and neuroendocrine stress responses. We hypothesized that women in an aerobic exercise group would show a significant improvement in aerobic capacity and reduction in cardiovascular and neuroendocrine stress responses relative to women who did not engage in aerobic exercise.
METHOD Subjects Fifty healthy premenopausal and postmenopausal women were recruited from newspaper, radio, and television advertisements to serve as subjects for this study. All participants were screened over the telephone to make sure that they were healthy, sedentary, between 45 and 57 years old, normotensive, and non-obese (less than 20% above normal weight as determined by Metropolitan Height and Weight Tables; Metropolitan Life Insurance Company, 1983). Subjects had not been engaged in regular exercise before their participation in the study. Subjects had not been taking any hormone, cardiac, or psychotropic medication. Menopausal status was confirmed by laboratory studies and menstrual history. Women were considered premenopausal if they had folliclestimulating hormone (FSH) levels of less than 40 mlu/ml, reported regular menstrual cycle lengths, and had not taken hormones orally in the past year. Women were excluded if they had been pregnant within the past 2 years. Women were considered postmenopausal if they had not experienced any menses in the 12 months preceding their participation in the study and had FSH levels of greater than 40 mlu/ml. Informed consent was obtained from each subject, and subjects who successfully completed the study were given a free 4-month access to the DUPAC (Duke University's Preventive Approach to Cardiology) exercise facility. Behavioral Stress Testing Subjects were tested before and after a 3-month exercise program. The testing protocol for each assessment was identical. All premenopausal women were tested at the same time of their menstrual cycle (luteal phase) for each session. All subjects were tested individually in a sound-attenuated, temperature-controlled (80 °F) chamber. An indwelling venous catheter was inserted 45 min before the baseline rest period, and the subject was asked to rest quietly so as to permit hormonal responses to the stress of venipuncture to return to baseline. Continuous venous blood samples were obtained using a Cormed blood withdrawal system (Model ML6-58, Cormed, Inc., Medina, NY) at a rate of .7 cc/min in the following fixed sequence: during an initial 15-min rest period, 5 min of public speaking, 10 min of rest, 3 min of cold stress, and a final 15-min rest period. The blood samples were spun down and the plasma frozen at — 70 °C until subsequent assay at the completion of the study. Catecholamines were assayed using high-performance liquid chromatography (Kilts, Gooch, 6 Knopes, 1984). The sensitivity was 5 pg/sample, and inter-assay and intra-assay coefficients of variation were less than 10%. HR and BP were monitored every minute with a Dinamap monitor (Model 845, Critikon, Tampa, FL). Each subject was tested between 12:30 and 2 p.m. and was asked to refrain from coffee, tea, and exercise during the day of the testing. For the public speaking task, each subject was told the following:
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BLUMENTHAL ET AL.
The first thing we want you to do is for you to give a short, five-minute speech. To simulate real-life conditions, we will be observing your speech in person so that we can evaluate the quality of your style of presentation as well as the content of what you say. At this point, I will give you one minute to prepare your speech. You can choose one of three topics. (For example: Should Martin Luther King Day be a national holiday? Is Star Wars a good way to spend federal funds? What can we do to prevent the destruction of rain forests in South America?) It is important for you to be specific and organized in your presentation. Pick one topic and take a minute to think about your speech; I'll come in to get you started in one minute. [One minute was allowed for preparation; two observers then returned and said the following.] Okay, what is your topic? [Subject states topic] Good. Okay, you have five minutes to deliver your speech. Remember, it is important for you to remain as still as possible and not to use your hands while speaking. You also must speak for the full five minutes and speak in a loud, clear voice so that we can understand you. You need to be specific and organized. Ready, begin. Following the speaking task, all subjects rested for 10 min and then underwent a 3-min cold challenge. Each subject was told the following: This is an ice pack. [An ice pack was placed on the subject's wrist so she could feel how cold it was and then she was told the following.] I will place it on your forehead for three minutes. If it becomes too painful during this time, just let me know and I will remove it. A 15-min recovery period concluded each session. Thus, blood and cardiovascular measures were obtained during the 15 min of baseline, 5 min of speech, 10 min of rest, 3 min of cold, and 15 min of recovery at the end of the session. Aerobic Fitness Graded treadmill exercise testing was conducted prior to exercise training using the Duke modification of the Balke protocol in which work load is increased at a rate of 1 metabolic equivalent (MET) per minute (Blumenthal, Rejeski et al., 1988). Fasting subjects exercised to exhaustion under continuous electrocardiographs monitoring. HR was obtained continuously with a Marquette Case 2 stress electrograph recorder (Milwaukee, WI). Expired air was collected by facemask for quantification of minute ventilation, oxygen (O2) consumption, and respiratory exchange ratio at 15-sec intervals with a MMC Horizon System 2 metabolic cart (Yorba Linda, CA). Borg ratings were obtained at each stage of the treadmill and at the completion of the test (Borg, 1982). Exercise Training Subjects were randomly assigned to one of two exercise programs. One group participated in aerobic exercise three times per week for 12 consecutive weeks. These sessions
consisted of 15 min of warm-up exercises including stretching and light biking on a stationary bicycle (less than 1 kp/min) followed by 35 min of continuous walking and jogging on a 400-m outdoor track at an intensity of at least 70% of subjects' initial peak O2 consumption (VO2), as determined by the initial treadmill test. HR was monitored three times per session by a trained exercise physiologist (Margo WalshRiddle) to ensure that subjects were within their prescribed training range. The other group participated in strength and flexibility training twice a week. Strength and flexibility training exercises consisted of 20 min of stretching and flexibility exercises followed by 30 min of circuit Nautilus training. Subjects in this non-aerobic exercise group did not engage in any aerobic exercise throughout the duration of the study. All subjects also were requested to maintain their usual dietary habits throughout the study. RESULTS The sample consisted of 50 healthy 45- to 57-year-old women. The premenopausal women were younger than the postmenopausal women (47 ± 2 years vs. 52 ± 3 years), F(l, 44) = 35.41, p < .0001, and, as expected, the premenopausal women had lower FSH levels than the postmenopausal women (13 ± 7 mlu/ml vs. 143 ± 48 mlu/ml), F(l, 44) = 165.98, p < .0001. Both premenopausal and postmenopausal women rated their health as good or excellent on a 4-point rating scale. All subjects had at least a high school education, and only two were active smokers. Table 1 depicts the characteristics of the two groups. Differences Between Premenopausal and Postmenopausal Women at Initial Examination Aerobic Fitness A one-way multivariate analysis of variance (MANOVA) was performed with peak VO2, HR at rest, HR at a submaxiTABLE 1 Demographic Characteristics of Sample Menopausal Status Characteristic Age (years) Percentage married Health rating (percentage) Excellent Good Fair Poor Education (years) FSH (mlu/ml) Weight (lb) Height (in.) Race (percentage White) Hysterectomy (n) Former/current smokers (n)
Premenopausal 47
± 2 73.9
52.2 43.5 4.4 0 13..8 ± 1.9 13..0 ± 7.5 146 ± 19 65 ± 2 91.3 6/1
Postmenopausal 52
± 3* 78.3
43.5 56.5 0.0 0 14..4 ± 1.7 143.,3 ± 47.9* 147 ± 19 64 ± 3 100 7 11/1
Notes. Data are M ± SD, except as noted otherwise. For both groups, n = 23. *p < .001.
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mal work load (5 METs), and total time on treadmill as the dependent variables. Table 2 highlights the treadmill performance for both groups. There was no overall effect for menopausal status, F(4, 37) = 1.57,/? < .20.
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Behavioral Stressors Measurements were obtained at rest, during the task, and at recovery for the speech and cold tasks. HR and BP values, collected at 1-min intervals, were averaged for each condition. Epinephrine and norepinephrine concentrations were obtained at each condition, with blood sampled from the last 5 min of each rest period serving as the rest levels preceding each task. Analyses were performed on the mean cardiovascular and neuroendocrine responses obtained. Speech. To determine initial baseline (resting) differences in cardiovascular and neuroendocrine levels, a series of analyses of covariance (ANCOVAs) was performed with age as a covariate. The only significant effect was for epinephrine, F(l, 34) = 4.92,/? < .04, with premenopausal women having higher resting levels than postmenopausal women (least squares means [LSMs] = 54.5 vs. 24.6 pg/ml). There were no significant differences between premenopausal and postmenopausal women on any of the resting cardiovascular measures. In addition, partial correlation coefficients — partialing out age —of FSH levels and initial resting cardiovascular and neuroendocrine values were not significant. An ANCOVA was used to assess cardiovascular and neuroendocrine reactivity to the speaking task, with menopausal status serving as a between-subjects factor and resting levels prior to each task and age serving as covariates. There were no differences between premenopausal and postmenopausal women with respect to cardiovascular reactivity to the speech.1 The ANCOVA for epinephrine reactivity was significant, F(l, 33) = 6.39,/? < .02, with postmenopausal women more reactive than premenopausal women (LSMs = 181.0 vs. 76.8 pg/ml). There was no difference in norepinephrine reactivity. Thus, postmenopausal women had lower resting levels of epinephrine and greater reactivity. In addition, partial correlations of cardiovascular and neuroendocrine reactivity — task level partialing out baseline and age —were correlated with FSH levels. Epinephrine (r = .57, p < .002) and diastolic BP (DBP; r = .33,/? < .04) were related to FSH levels, with postmenopausal (i.e., higher FSH) women exhibiting greater reactivity. Cold. The ANCOVAs for cardiovascular and neuroendocrine measures during the cold stress did not reveal any significant effects for menopausal status. The partial correlations of FSH levels and cardiovascular and neuroendocrine reactivity to the cold stress were small and did not reach statistical significance.
'Premenopausal women had greater HR reactivity than postmenopausal women during the speech task (96 ± 12 bpm vs. 89 ± 12 bpm, p < .05) when age was not included as a covariate.
TABLE 2 Aerobic Fitness for Premenopausal and Postmenopausal Women Menopausal Status Premenopausal Measure Resting HR (bpm) HR at 5 METs (bpm) Peak VO2 (ml/kg/min) Time on treadmill (min)
Postmenopausal
M
SD
M
SD
79 130.2 27.0 9.5
11 10.3 4.8 1.4
75 128.7 25.7 8.9
8 11.8 3.8 1.0
Note. For both groups, n = 23.
Effects of Exercise Training Aerobic Fitness Forty-six (23 premenopausal, 23 postmenopausal) women completed the exercise programs. Twenty-two completed the strength training program (M =24.7 sessions out of 242), and 24 completed the aerobic training program (M = 35.4 sessions out of 36). Subjects in the aerobic group were at or above their prescribed HR training range 77% of the time (range = 58% to 100%) and reported moderate levels of physical exertion — using the Borg (1982) rating system (M = 13 rating of perceived exertion) — during their training sessions. To assess cardiovascular training effects on fitness, a three-way (Status x Group x Time) repeated-measure MANOVA was performed. Significant multivariate main effects were found for group, F(4, 36) = 6.46, p < .0005, and time, F(4, 39) = 12.62, p < .0001; a significant Group x Time interaction, F(4, 36) = 9.05,/? < .0001, was also found. For resting HR, there was a significant univariate effect for time, F(l, 42) = 26.49, p < .0001, and a significant Time x Group interaction, F(l, 39) = 5.32, p < .03. Table 3 shows that the aerobic group achieved a 7-beat reduction in resting HR, whereas the strength group achieved only a 3-beat reduction in resting HR. For HR at 5 METs, there was a main effect for time, F(l, 42) = 25.22,/? < .0001, with both groups experiencing a decrease in HR at submaximal work loads (Table 3). Examination of the univariate effects for the duration of exercise on the treadmill revealed significant main effects for group, F(\, 39) = 16.23,/? < .0003, and time, F(l, 42) = 24.35, /? < .0001, and a significant Group x Time interaction, F(l, 39) = 21.55,/? < .0001. The aerobic group increased its treadmill time by 1.5 min, F(l, 22) = 60.31, /? < .0001, whereas the treadmill time for the strength group did not change, F(l, 21) = 0.54, p < .49. The univariate effects for peak VO2 revealed significant effects for group, F(l, 39) = 5.34,/? < .03, and time, F(l, 42) = 16.43, p < .0002, and a significant Group x Time interaction, F(l, 39) = 21.59,/? < .0001. The aerobic group increased its peak VO2 by almost 20%, F(l, 21) = 35.22, p < .0001, whereas the peak VO2 for the strength group did not change. Thus, the two exercise groups experienced different patterns of change. As expected, participants in the aerobic 2
Several subjects attended extra classes.
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BLUMENTHAL ET AL. TABLE 3 Changes in Aerobic Fitness for Strength and Aerobic Groups Exercise Group Aerobicb
Strenth* Time 1 Measure
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Resting HR (bpm) HR at 5 METs (bpm) Peak VO2 (ml/kg/min) Time on treadmill (min)
Time 2
Time 1
Time 2
M
SD
M
SD
M
SD
M
SD
79 134.6 26.1 8.8
10 11.0 4.5 1.1
76 127.5 26.0 8.9
9 11.0 4.6 1.3
75 131.4 26.7 9.6
9 11.8 4.2 1.2
68* 124.1 31.6** 11.1**
9 13.8 5.9 1.7
a
« = 22. bn = 24. *p < .001. **p < .0001.
group increased their aerobic fitness, whereas participants in the strength group did not improve their aerobic fitness. Premenopausal and postmenopausal women experienced comparable improvements in aerobic capacity. In addition, subjects in both groups lost a comparable amount of body weight (mean weight at Time 1 = 146 ± 19 lb, mean weight at Time 2 = 145 ± 19 lb). Responses to Behavioral Stressors Speech. The mean values for the cardiovascular and neuroendocrine responses are presented in Table 4. To assess the effects of exercise training on cardiovascular and neuroendocrine responses to the speaking task, a series of ANCOVAs was performed for HR, SBP, DBP, epinephrine, and norepinephrine with task level at Time 1 and age as covariates. Only HR was significant, with subjects in the aerobic group having lower levels than those of subjects in the strength group (82 vs. 89 bpm, p < .05). To assess reactivity, ANCOVAs with age, resting values at Time 1 and Time 2, and task levels at Time 1 as covariates did not reveal any significant group effects or Group x Menopausal Status interactions for BP, epinephrine, or norepinephrine. Cold. A series of ANCOVAs was employed to evaluate the effects of the two exercise conditions on responses to the cold challenge. Results of the ANCOVA revealed a significant Group x Menopausal Status interaction for DBP, F(2, 40) = 5.99, p < .006, and SBP, F(2, 40) = 6.70, p < .004. For the postmenopausal women, participants in the aerobic group had lower DBP (LSMs = 77 vs. 83 mm Hg, p < .03) and SBP (LSMs = 126 vs. 135mmHg,/7 < .04) than participants in the strength group. Unexpectedly, however, premenopausal women showed the opposite pattern: Participants in the strength group had lower DBP (LSMs = 74 vs. 80 mm Hg, p < .04) and lower SBP (LSMs = 121 vs. 132 mm Hg,/? < .02). There were no group differences in neuroendocrine levels during the cold challenge after exercise training. Significant Group X Menopausal Status effects were found for DBP, F(2, 38) = 3.65, p < .04, and SBP, F(2, 38) = 3.58, p < .04, reactivity. Post hoc tests revealed that postmenopausal women in the aerobic group had lower DBP reactivity than postmenopausal women in the strength group
(LSMs = 75.9 vs. 82.1 mm Hg, p < .03) and tended to have lower SBP reactivity (LSMs = 124.7 vs. 133.1 mm Hg, p < .06). There were no differences in reactivity among the premenopausal women in the aerobic and strength groups (LSMs: SBP = 131.5 vs. 124.5 mm Hg, DBP = 79.1 vs. 75.9 mm Hg). DISCUSSION This study investigated the potential influence of reproductive hormones and aerobic exercise training on psychophysiological stress responses. Results showed that premenopausal and postmenopausal women generally exhibited comparable cardiovascular stress responses prior to exercise training. On the other hand, postmenopausal women displayed lower resting levels and greater epinephrine reactivity to the speaking task. The results of the study provide partial support for the results reported from the only other study of psychophysiological responses of similar-age premenopausal and postmenopausal women. Saab et al. (1989) reported that postmenopausal women had higher HR, SBP, and epinephrine levels during speech performance than premenopausal women did. In terms of aerobic training, the women in our study achieved aerobic capacity improvements comparable to those of men who have undergone identical exercise training protocols (Blumenthal, Emery et al., 1988; Blumenthal et al., 1990). Moreover, premenopausal and postmenopausal women experienced similar improvements in peak VO2. Thus, our results indicate that reproductive hormones do not appear to influence the magnitude of cardiopulmonary training effects in response to aerobic exercise. When the effects of exercise training on stress reactivity were considered, results provided only partial support for our previous findings (e.g., Blumenthal et al., 1990). Although women in the aerobic group had HR levels lower than those of the strength group during the speech task, this advantage became nonsignificant when resting levels at Time 1 and Time 2 were added as covariates. This pattern suggests that HR levels during stress —but not reactivity—may be reduced by aerobic exercise training. With respect to the cold challenge, an interesting and somewhat inconsistent pattern emerged. Aerobic exercise for the postmenopausal women, but not for the premenopausal
TABLE 4 Cardiovascular and Neuroendocrine Values at Baseline (Rest 1), Speech, Rest 2, Cold, and Rest 3 for Premenopausal and Postmenopausal Women Before (Time 1) and After (Time 2) Aerobic or Strength Training Menopausal Status Premenopausal
Postmenopausal Strength b
Aerobic? Measure HR (bpm) Rest 1 Speech
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Rest 2 Cold Rest 3 SBP (mm Hg) Rest 1 Speech Rest 2 Cold Rest 3 DBP (mm Hg) Rest 1 Speech Rest 2 Cold Rest 3 Epinephrine (pg/ml) Rest 1 Speech Rest 2 Cold Rest 3 Norepinephrine (pg/ml) Rest 1 Speech Rest 2 Cold Rest 3
Time 1
Time 2
Strength b
Aerobic*
Time 1
Time 2
Time 1
Time 2
Time 1
Time 2
75 (8) 98 (12) 77 (7) 75 (6) 75 (6)
70 (8) 87 (9) 68 (6) 68 (6) 68 (7)
73 (5) 94 (12) 74 (5) 74 (6) 72 (5)
72 (6) 91 (10) 72 (6) 71 (9) 71 (6)
73 (10) 84 (10) 73 (10) 73 (11) 71 (9)
69 (10) 78 (8) 68 (10) 69 (9) 68 (10)
74 (8) 95 (11) 75 (8) 73 (8) 72 (6)
73 (7) 88 (13) 72 (6) 69 (9) 69 (6)
115 (15) 155 (18) 125 (14) 135 (21) 118 (11)
115 (11) 149 (17) 121 (12) 134 (19) 117 (13)
107 (10) 141 (15) 116 (11) 121 (15) 110 (7)
102 (4) 134 (15) 109 (5) 114 (10) 105 (5)
117 (11) 146 (14) 121 (13) 140 (16) 121 (15)
115 (11) 140 (14) 122 (12) 130 (13) 117 (12)
118 (11) 156 (13) 129 (11) 133 (12) 121 (9)
120 (9) 147 (14) 124 (9) 135 (12) 120 (10)
72 (12) 92 (14) 76 (12) 83 (14) 74 (10)
73 (10) 89 (13) 74 (11) 85 (15) 72 (10)
64 (5) 82 (7) 66 (5) 72 (9) 64 (6)
61 (3) 79 (9) 62 (4) 69 (8) 62 (3)
70 (9) 87 (10) 71 (9) 82 (9) 71 (9)
69 (7) 85 (11) 72 (8) 78 (9) 71 (7)
71 (11) 94 (12) 73 (11) 79 (10) 72 (11)
72 (9) 88 (12) 72 (8) 82 (10) 72 (10)
56 (41) 121 (68) 65 (41) 59 (35) 49 (37)
35 (23) 66 (42) 35 (14) 49 (30) 52 (27)
30 (18) 93 (55) 40 (21) 49 (33) 49 (45)
54 (45) 66 (40) 60 (23) 47 (35) 44 (41)
41 (40) 99 (101) 40 (31) 48 (38) 39 (33)
24 (18) 74 (68) 32 (24) 33 (24) 30 (24)
30 (22) 102 (57) 44 (19) 44 (20) 47 (21)
33 (23) 96 (69) 36 (21) 51 (21) 37 (17)
329 (158) 461 (182) 343 (171) 462 (258) 429 (256)
377 (225) 497 (264) 359 (148) 490 (253) 402 (177)
280 (131) 378 (171) 251 (115) 318 (124) 284 (95)
365 (157) 401 (211) 233 (93) 303 (123) 307 (133)
258 (127) 385 (110) 253 (76) 395 (113) 349 (103)
236 (85) 376 (117) 221 (52) 327 (97) 298 (111)
330 (116) 441 (161) 317 (74) 398 (163) 355 (117)
289 (99) 458 (259) 310 (135) 486 (312) 328 (193)
Note. Means are unadjusted for age; standard deviations are in parentheses. a n = 12. bn = 11.
389
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BLUMENTHAL ET AL.
women, was associated with significantly lower BP levels and an attenuation of BP reactivity compared to strength training. However, premenopausal women in the strength group (compared to the aerobic group) exhibited lower BP levels. We have no explanation for this finding. Unfortunately, one limitation of our study was that we did not include a nonexercise control group. Consequently, we were unable to distinguish the effects of any exercise (aerobic or strength training) from the effects of no exercise at all. There are several important differences between the present study and our previous work — involving the selection of stressors and the nature of the subject population. In both our previous studies, we employed a moderate stressor — mental arithmetic — that generally elicited a 10-bpm increase in HR, a 10- to 15-mm Hg increase in SBP, and a 5- to 10-mm Hg increase in DBP. In contrast, the public speaking task was twice as potent; HR increased more than 20 bpm, and SBP and DBP increased by almost 40 mm Hg and 20 mm Hg, respectively. It is possible that aerobic exercise may attenuate psychophysiologic responses to low to moderate stressors but not to more intense stressors. The present study was also the first to employ a cold challenge, which yielded inconsistent results. In addition, in our previous work we studied Type A men; in the present study, women were not preselected on the basis of their being Type A. Differences in the nature of the stressors and in certain individual characteristics may have contributed to the different pattern of results. A final factor that may be relevant is the fitness levels of study subjects. Post hoc analyses by Holmes and McGilley (1987) revealed that aerobic exercise reduced HR levels during a memory task among a subgroup of unfit young (17- to 20-year-old) women but not among more fit women. It is difficult to compare their results to ours, however, because Holmes and McGilley only estimated levels of aerobic fitness, and we measured aerobic power directly with expired gas analyses. However, it is unlikely that different levels of fitness were responsible for the inconsistency of the present findings and those of our previous work with men, as the women in this study were all sedentary, with an average aerobic capacity— less than 8 METs — that was less than that obtained for men of similar age. In conclusion, our findings indicate that a program of aerobic exercise may serve to reduce levels of cardiovascular response to behavioral stressors among middle-aged women. However, reproductive hormones, along with the nature of the stressor, may affect this response. Future research should attempt to clarify the role of aerobic exercise in reducing stress responses, including identifying individual-difference factors (e.g., Type A vs. Type B, fit vs. unfit, or young vs. old individuals), task characteristics (e.g., mild stressors vs. moderate stressors, alpha- vs. beta-adrenergic tasks), and exercise training regimens (e.g., aerobic vs. non-aerobic exercise, moderate- vs. high-intensity exercise) that may account for some of the inconsistencies in the results. ACKNOWLEDGMENTS Manuscript preparation was supported by National Institutes of Health Grants HL 30675 and AG 04238 and by a grant
from the John D. and Catherine T. MacArthur Network on the Determinants and Consequences of Health-Promoting and Health-Damaging Behavior. We thank Margo Walsh-Riddle, Sally Schnitz, and Robin Pomeroy for their technical assistance and Janet Ivey for her secretarial assistance. REFERENCES Blumenthal, J. A., Emery, C. F., Walsh, M. A., Cox, D. R., Kuhn, C. M., Williams, R. B., & Williams, R. S. (1988). Exercise training in healthy Type A middle-aged men: Effects on behavioral and cardiovascular responses. Psychosomatic Medicine, 50, 418-433. Blumenthal, J. A., Fredrikson, M., Kuhn, C. M., Ulmer, R. L., Walsh-Riddle, M., & Appelbaum, M. (1990). Aerobic exercise reduces levels of cardiovascular and sympathoadrenal responses to mental stress in subjects without prior evidence of myocardial ischemia. American Journal of Cardiology, 65, 93-98. Blumenthal, J. A., Rejeski, W. J., Walsh-Riddle, M., Emery, C. F., Miller, H., Roark, S., Ribisl, P. M., Morris, P. B., Brubaker, P., & Williams, R. S. (1988). Comparison of high- and low-intensity exercise training early after acute myocardial infarction. American Journal of Cardiology, 61, 26-30. Borg, G. (1982). Psychophysiological bases of perceived exertion. Medicine and Science in Sports and Exercise, 14, 377-387. Collins, A., & Frankenhaueser, M. (1978). Stress responses in male and female engineering students. Journal of Human Stress, 4, 43-48. Crews, D. J., & Landers, D. M. (1987). A meta-analytic review of aerobic fitness and reactivity to psychosocial stressors. Medicine and Science in Sports and Exercise, 19, S114-S120. Frankenhaueser, M. (1983). The sympathetic-adrenal and pituitaryadrenal response to challenge: Comparison between the sexes. In T. M. Dembroski, T. H. Schmidt, & G. Blumchen (Eds.), Biobehavioral bases of coronary heart disease (pp. 91-105). Basel, Switzerland: Karger. Frankenhaueser, M., Dunne, E., & Lundberg, U. (1976). Sex differences in sympathetic-adrenal medullary reactions induced by different stressors. Psychopharmacology, 47, 1-5. Frankenhaueser, M., Lundberg, U., & Forsman, L. (1980). Dissociation between sympathetic-adrenal and pituitary-adrenal responses to an achievement situation characterized by high controllability: Comparison between Type A and Type B males and females. Biological Psychology, 10, 79-91. Holmes, D. S., & McGilley, B. M. (1987). Influence of a brief aerobic training program on heart rate and subjective response to a psychologic stressor. Psychosomatic Medicine, 49, 366-374. Johansson, G. (1972). Sex differences in the catecholamine output of children. Acta Physiologica Scandinavica, 86, 569-572. Johansson, G., & Post, B. (1973). Catecholamine output in school children as related to performance and adjustment. Scandinavian Journal of Psychology, 14, 20-28. Kilts, C. D., Gooch, M. D., &Knopes, K. D. (1984). Quantitation of plasma catecholamines by on-line trace enrichment high performance liquid chromatography with electrochemical detection. Journal of Neuroscience Methods, 11, 257-273. Krantz, D. S., & Manuck, S. B. (1984). Acute psychophysiologic reactivity and risk of cardiovascular disease: A review and methodologic critique. Psychological Bulletin, 96, 435-464. Lundberg, U. (1983). Sex differences in behavior pattern and catecholamine and cortisol excretion in 3-6 year old day-care children. Biological Psychology, 16, 109-117. Manuck, S. B., & Polefrone, J. M. (1987). Psychophysiologic reaptivity in women. In E. D. Eaker, B. Packard, N. C. Wenger, T. B»
This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly.
STRESS REACTIVITY, EXERCISE, MENOPAUSE Clarkson, & H. A. Tyroler (Eds.), Coronary heart disease in women (pp. 164-171). New York: Haymarket Dogma. Matthews, K. A., & Stoney, C. M. (1988). Influences of sex and age on cardiovascular responses during stress. Psychosomatic Medicine, 50, 46-56. Matthews, K. A., Weiss, S. M., Detre, T., Dembroski, T. M., Falkner, B.( Manuck, S. B.( & Williams, R. B. (Eds.). (1986). Handbook of stress, reactivity, and cardiovascular disease. New York: Wiley. Metropolitan Life Insurance Company. (1983). Metropolitan Height and Weight Tables. Statistical Bulletin of the Metropolitan Life Insurance Company, 64, 2-9. Roskies, E., Seraganian, P., Oseasohn, R., Hanley, J. A., Collu, R., Martin, N., & Smilga, C. (1986). The Montreal Type A Intervention Project: Major findings. Health Psychology, 5, 45-69. Saab, P. G., Matthews, K. A., Stoney, C. M., & McDonald, R. H. (1989). Premenopausal and postmenopausal women differ in their cardiovascular and neuroendocrine responses to behavioral stressors. Psychophysiology, 26, 270-280. Shapiro, A. P. (1961). An experimental study of comparative responses of blood pressure to different noxious stimuli. Journal of
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Chronic Diseases, 13, 293-311. Sherwood, A., Light, K. C , & Blumenthal, J. A. (1989). Effects of aerobic exercise training on hemodynamic responses during psychosocial stress in normotensive and borderline hypertensive Type A men: A preliminary report. Psychosomatic Medicine, 51, 123-136. Sinyor, D., Golden, M., Steinert, Y., & Seraganian, P. (1986). Experimental manipulation of aerobic fitness and the response to psychosocial stress: Heart rate and self-report measures. Psychosomatic Medicine, 48, 324-337. Sinyor, D., Peronnet, F., Brisson, G., & Seraganian, P. (1987). Failure to alter sympathoadrenal response to psychosocial stress following aerobic training. Physiology & Behavior, 42, 293-296. Steptoe, A., Moses, J., Mathews, A., & Edwards, S. (1990). Aerobic fitness, physical activity, and psychophysiological reactions to mental tasks. Psychophysiology, 27, 264-275. Stoney, C. M., Davis, M. C , & Matthews, K. A. (1987). Sex differences in physiological responses to stress and in coronary heart disease: A causal link? Psychophysiology, 24, 127-131. World Health Organization. (1980). Vital statistics and causes of death (World Health Statistics Annual). Geneva: Author.
Stress Reactivity and Exercise Training in Premenopausal and Postmenopausal Women James A. Blumenthal Department of Psychiatry Duke University Medical Center
This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly.
Mats Fredrikson Department of Psychiatry and Psychology Karolinska Institute and Stockholm University
Karen A. Matthews Department of Psychiatry University of Pittsburgh School of Medicine
Cynthia M. Kuhn Department of Pharmacology Duke University Medical Center
Susan Schniebolk Department of Psychiatry Duke University Medical Center
Deborah German Department of Medicine Vanderbilt University
Nader Rifai Department of Laboratory Medicine Children's National Medical Center
John Steege Department of Obstetrics and Gynecology Duke University Medical Center
Judith Rodin Yale University Examined the influence of ovarian function on psychophysiological stress responses and determined if aerobic exercise reduced stress reactivity. Fifty premenopausal and postmenopausal women initially were subjected to a public speaking task and an ice-on-the-forehead procedure, during which time their blood pressure and heart rate were monitored and continuous blood samples were obtained. Subjects also underwent aerobic fitness evaluations with a maximum-exercise treadmill test. Subjects were then randomly assigned to a 12-week exercise program of either aerobic exercise (e.g., walking and jogging at a prescribed exercise intensity) or non-aerobic strength and flexibility training and were then reevaluated. Results indicated that postmenopausal women exhibited lower resting epinephrine levels but greater epinephrine reactivity to the speaking task compared to the premenopausal women. There were no differences between premenopausal and postmenopausal women with respect to cardiovascular or catecholamine responses during the cold challenge. Premenopausal and postmenopausal women also achieved comparable improvements in aerobic fitness. However, results of the mental stress testing were complex and provided only partial support for the role of aerobic exercise in reducing stress responses. Key words: aerobic exercise, weight training, reproductive hormones, physiological reactivity Coronary heart disease (CHD) is a significant health problem for women as well as for men. In most industrialized coun-
Requests for reprints should be sent to James A. Blumenthal, Department of Psychiatry, Duke University Medical Center, Box 3119, Durham, NC 27710.
tries, CHD accounts for about one third of all deaths in women (World Health Organization, 1980). The traditional risk factors —hypertension, hyperlipidemia, and cigarette smoking —appear to be at least as important for women as they are for men. Other factors also are likely, however, and investigators have focused on biobehavioral influences that may be relevant for the development of CHD in women.
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STRESS REACTIVITY, EXERCISE, MENOPAUSE
This study examined two related issues. First, research has shown that exaggerated physiological responses to behavioral stimuli may contribute to CHD (Krantz & Manuck, 1984; Matthews et al., 1986). Because menopause is not only associated with increased risk of CHD but is also accompanied by significant hormonal changes, the influence of ovarian function on psychophysiological reactivity to stress has received increased attention (Manuck & Polefrone, 1987). For example, studies have indicated that, during various challenging stressors, women compared to men tend to exhibit greater heart rate (HR) responsivity but that women have smaller blood pressure (BP) and epinephrine stress responses compared to men (Collins & Frankenhaueser, 1978; Frankenhaueser, 1983; Frankenhaueser, Dunne, & Lundberg, 1976; Frankenhaueser, Lundberg, & Forsman, 1980; Johansson, 1972; Johansson & Post, 1973; Lundberg, 1983; Matthews & Stoney, 1988; Shapiro, 1961; Stoney, Davis, & Matthews, 1987). Studies of hormonal influences on cardiovascular stress reactivity have also compared premenopausal and postmenopausal women. Saab, Matthews, Stoney, and McDonald (1989) showed that postmenopausal women exhibited greater increases in HR, systolic BP (SBP), and epinephrine than did premenopausal women during a public speaking task; however, there were no BP or catecholamine differences among premenopausal and postmenopausal women during several other tasks including mental arithmetic, mirror-image tracing, and postural tilt. In the present study, we compared premenopausal and postmenopausal women's cardiovascular and neuroendocrine responses to two different behavioral stressors —a public speaking task and a cold challenge. We hypothesized that postmenopausal women would be more reactive than premenopausal women on the speech task but not during the cold task. A second issue of interest concerned the physiologic effects of exercise. Previous studies, mostly of men, have reported that aerobic exercise training may attenuate cardiovascular and neuroendocrine responses to stress. Cross-sectional comparisons of fit and unfit individuals have generally shown that fit subjects exhibit reduced cardiovascular stress responses compared to unfit subjects (Crews & Landers, 1987). However, few studies of adult women have been reported. Moreover, randomized longitudinal studies of men have yielded inconsistent findings. To our knowledge, only three studies have shown that aerobic exercise training reduces cardiovascular stress responses (Blumenthal, Emery et al., 1988; Blumenthal et al., 1990; Sherwood, Light, & Blumenthal, 1989). Other studies have been either equivocal (Sinyor, Golden, Steinert, & Seraganian, 1986) or negative (Roskies et al., 1986; Sinyor, Peronnet, Brisson, & Seraganian, 1987; Steptoe, Moses, Mathews, & Edwards, 1990). The present investigation examined the changes in aerobic capacity in a group of middle-aged women and assessed the effects of aerobic fitness on cardiovascular and neuroendocrine stress responses. We hypothesized that women in an aerobic exercise group would show a significant improvement in aerobic capacity and reduction in cardiovascular and neuroendocrine stress responses relative to women who did not engage in aerobic exercise.
METHOD Subjects Fifty healthy premenopausal and postmenopausal women were recruited from newspaper, radio, and television advertisements to serve as subjects for this study. All participants were screened over the telephone to make sure that they were healthy, sedentary, between 45 and 57 years old, normotensive, and non-obese (less than 20% above normal weight as determined by Metropolitan Height and Weight Tables; Metropolitan Life Insurance Company, 1983). Subjects had not been engaged in regular exercise before their participation in the study. Subjects had not been taking any hormone, cardiac, or psychotropic medication. Menopausal status was confirmed by laboratory studies and menstrual history. Women were considered premenopausal if they had folliclestimulating hormone (FSH) levels of less than 40 mlu/ml, reported regular menstrual cycle lengths, and had not taken hormones orally in the past year. Women were excluded if they had been pregnant within the past 2 years. Women were considered postmenopausal if they had not experienced any menses in the 12 months preceding their participation in the study and had FSH levels of greater than 40 mlu/ml. Informed consent was obtained from each subject, and subjects who successfully completed the study were given a free 4-month access to the DUPAC (Duke University's Preventive Approach to Cardiology) exercise facility. Behavioral Stress Testing Subjects were tested before and after a 3-month exercise program. The testing protocol for each assessment was identical. All premenopausal women were tested at the same time of their menstrual cycle (luteal phase) for each session. All subjects were tested individually in a sound-attenuated, temperature-controlled (80 °F) chamber. An indwelling venous catheter was inserted 45 min before the baseline rest period, and the subject was asked to rest quietly so as to permit hormonal responses to the stress of venipuncture to return to baseline. Continuous venous blood samples were obtained using a Cormed blood withdrawal system (Model ML6-58, Cormed, Inc., Medina, NY) at a rate of .7 cc/min in the following fixed sequence: during an initial 15-min rest period, 5 min of public speaking, 10 min of rest, 3 min of cold stress, and a final 15-min rest period. The blood samples were spun down and the plasma frozen at — 70 °C until subsequent assay at the completion of the study. Catecholamines were assayed using high-performance liquid chromatography (Kilts, Gooch, 6 Knopes, 1984). The sensitivity was 5 pg/sample, and inter-assay and intra-assay coefficients of variation were less than 10%. HR and BP were monitored every minute with a Dinamap monitor (Model 845, Critikon, Tampa, FL). Each subject was tested between 12:30 and 2 p.m. and was asked to refrain from coffee, tea, and exercise during the day of the testing. For the public speaking task, each subject was told the following:
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BLUMENTHAL ET AL.
The first thing we want you to do is for you to give a short, five-minute speech. To simulate real-life conditions, we will be observing your speech in person so that we can evaluate the quality of your style of presentation as well as the content of what you say. At this point, I will give you one minute to prepare your speech. You can choose one of three topics. (For example: Should Martin Luther King Day be a national holiday? Is Star Wars a good way to spend federal funds? What can we do to prevent the destruction of rain forests in South America?) It is important for you to be specific and organized in your presentation. Pick one topic and take a minute to think about your speech; I'll come in to get you started in one minute. [One minute was allowed for preparation; two observers then returned and said the following.] Okay, what is your topic? [Subject states topic] Good. Okay, you have five minutes to deliver your speech. Remember, it is important for you to remain as still as possible and not to use your hands while speaking. You also must speak for the full five minutes and speak in a loud, clear voice so that we can understand you. You need to be specific and organized. Ready, begin. Following the speaking task, all subjects rested for 10 min and then underwent a 3-min cold challenge. Each subject was told the following: This is an ice pack. [An ice pack was placed on the subject's wrist so she could feel how cold it was and then she was told the following.] I will place it on your forehead for three minutes. If it becomes too painful during this time, just let me know and I will remove it. A 15-min recovery period concluded each session. Thus, blood and cardiovascular measures were obtained during the 15 min of baseline, 5 min of speech, 10 min of rest, 3 min of cold, and 15 min of recovery at the end of the session. Aerobic Fitness Graded treadmill exercise testing was conducted prior to exercise training using the Duke modification of the Balke protocol in which work load is increased at a rate of 1 metabolic equivalent (MET) per minute (Blumenthal, Rejeski et al., 1988). Fasting subjects exercised to exhaustion under continuous electrocardiographs monitoring. HR was obtained continuously with a Marquette Case 2 stress electrograph recorder (Milwaukee, WI). Expired air was collected by facemask for quantification of minute ventilation, oxygen (O2) consumption, and respiratory exchange ratio at 15-sec intervals with a MMC Horizon System 2 metabolic cart (Yorba Linda, CA). Borg ratings were obtained at each stage of the treadmill and at the completion of the test (Borg, 1982). Exercise Training Subjects were randomly assigned to one of two exercise programs. One group participated in aerobic exercise three times per week for 12 consecutive weeks. These sessions
consisted of 15 min of warm-up exercises including stretching and light biking on a stationary bicycle (less than 1 kp/min) followed by 35 min of continuous walking and jogging on a 400-m outdoor track at an intensity of at least 70% of subjects' initial peak O2 consumption (VO2), as determined by the initial treadmill test. HR was monitored three times per session by a trained exercise physiologist (Margo WalshRiddle) to ensure that subjects were within their prescribed training range. The other group participated in strength and flexibility training twice a week. Strength and flexibility training exercises consisted of 20 min of stretching and flexibility exercises followed by 30 min of circuit Nautilus training. Subjects in this non-aerobic exercise group did not engage in any aerobic exercise throughout the duration of the study. All subjects also were requested to maintain their usual dietary habits throughout the study. RESULTS The sample consisted of 50 healthy 45- to 57-year-old women. The premenopausal women were younger than the postmenopausal women (47 ± 2 years vs. 52 ± 3 years), F(l, 44) = 35.41, p < .0001, and, as expected, the premenopausal women had lower FSH levels than the postmenopausal women (13 ± 7 mlu/ml vs. 143 ± 48 mlu/ml), F(l, 44) = 165.98, p < .0001. Both premenopausal and postmenopausal women rated their health as good or excellent on a 4-point rating scale. All subjects had at least a high school education, and only two were active smokers. Table 1 depicts the characteristics of the two groups. Differences Between Premenopausal and Postmenopausal Women at Initial Examination Aerobic Fitness A one-way multivariate analysis of variance (MANOVA) was performed with peak VO2, HR at rest, HR at a submaxiTABLE 1 Demographic Characteristics of Sample Menopausal Status Characteristic Age (years) Percentage married Health rating (percentage) Excellent Good Fair Poor Education (years) FSH (mlu/ml) Weight (lb) Height (in.) Race (percentage White) Hysterectomy (n) Former/current smokers (n)
Premenopausal 47
± 2 73.9
52.2 43.5 4.4 0 13..8 ± 1.9 13..0 ± 7.5 146 ± 19 65 ± 2 91.3 6/1
Postmenopausal 52
± 3* 78.3
43.5 56.5 0.0 0 14..4 ± 1.7 143.,3 ± 47.9* 147 ± 19 64 ± 3 100 7 11/1
Notes. Data are M ± SD, except as noted otherwise. For both groups, n = 23. *p < .001.
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STRESS REACTIVITY, EXERCISE, MENOPAUSE
mal work load (5 METs), and total time on treadmill as the dependent variables. Table 2 highlights the treadmill performance for both groups. There was no overall effect for menopausal status, F(4, 37) = 1.57,/? < .20.
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Behavioral Stressors Measurements were obtained at rest, during the task, and at recovery for the speech and cold tasks. HR and BP values, collected at 1-min intervals, were averaged for each condition. Epinephrine and norepinephrine concentrations were obtained at each condition, with blood sampled from the last 5 min of each rest period serving as the rest levels preceding each task. Analyses were performed on the mean cardiovascular and neuroendocrine responses obtained. Speech. To determine initial baseline (resting) differences in cardiovascular and neuroendocrine levels, a series of analyses of covariance (ANCOVAs) was performed with age as a covariate. The only significant effect was for epinephrine, F(l, 34) = 4.92,/? < .04, with premenopausal women having higher resting levels than postmenopausal women (least squares means [LSMs] = 54.5 vs. 24.6 pg/ml). There were no significant differences between premenopausal and postmenopausal women on any of the resting cardiovascular measures. In addition, partial correlation coefficients — partialing out age —of FSH levels and initial resting cardiovascular and neuroendocrine values were not significant. An ANCOVA was used to assess cardiovascular and neuroendocrine reactivity to the speaking task, with menopausal status serving as a between-subjects factor and resting levels prior to each task and age serving as covariates. There were no differences between premenopausal and postmenopausal women with respect to cardiovascular reactivity to the speech.1 The ANCOVA for epinephrine reactivity was significant, F(l, 33) = 6.39,/? < .02, with postmenopausal women more reactive than premenopausal women (LSMs = 181.0 vs. 76.8 pg/ml). There was no difference in norepinephrine reactivity. Thus, postmenopausal women had lower resting levels of epinephrine and greater reactivity. In addition, partial correlations of cardiovascular and neuroendocrine reactivity — task level partialing out baseline and age —were correlated with FSH levels. Epinephrine (r = .57, p < .002) and diastolic BP (DBP; r = .33,/? < .04) were related to FSH levels, with postmenopausal (i.e., higher FSH) women exhibiting greater reactivity. Cold. The ANCOVAs for cardiovascular and neuroendocrine measures during the cold stress did not reveal any significant effects for menopausal status. The partial correlations of FSH levels and cardiovascular and neuroendocrine reactivity to the cold stress were small and did not reach statistical significance.
'Premenopausal women had greater HR reactivity than postmenopausal women during the speech task (96 ± 12 bpm vs. 89 ± 12 bpm, p < .05) when age was not included as a covariate.
TABLE 2 Aerobic Fitness for Premenopausal and Postmenopausal Women Menopausal Status Premenopausal Measure Resting HR (bpm) HR at 5 METs (bpm) Peak VO2 (ml/kg/min) Time on treadmill (min)
Postmenopausal
M
SD
M
SD
79 130.2 27.0 9.5
11 10.3 4.8 1.4
75 128.7 25.7 8.9
8 11.8 3.8 1.0
Note. For both groups, n = 23.
Effects of Exercise Training Aerobic Fitness Forty-six (23 premenopausal, 23 postmenopausal) women completed the exercise programs. Twenty-two completed the strength training program (M =24.7 sessions out of 242), and 24 completed the aerobic training program (M = 35.4 sessions out of 36). Subjects in the aerobic group were at or above their prescribed HR training range 77% of the time (range = 58% to 100%) and reported moderate levels of physical exertion — using the Borg (1982) rating system (M = 13 rating of perceived exertion) — during their training sessions. To assess cardiovascular training effects on fitness, a three-way (Status x Group x Time) repeated-measure MANOVA was performed. Significant multivariate main effects were found for group, F(4, 36) = 6.46, p < .0005, and time, F(4, 39) = 12.62, p < .0001; a significant Group x Time interaction, F(4, 36) = 9.05,/? < .0001, was also found. For resting HR, there was a significant univariate effect for time, F(l, 42) = 26.49, p < .0001, and a significant Time x Group interaction, F(l, 39) = 5.32, p < .03. Table 3 shows that the aerobic group achieved a 7-beat reduction in resting HR, whereas the strength group achieved only a 3-beat reduction in resting HR. For HR at 5 METs, there was a main effect for time, F(l, 42) = 25.22,/? < .0001, with both groups experiencing a decrease in HR at submaximal work loads (Table 3). Examination of the univariate effects for the duration of exercise on the treadmill revealed significant main effects for group, F(\, 39) = 16.23,/? < .0003, and time, F(l, 42) = 24.35, /? < .0001, and a significant Group x Time interaction, F(l, 39) = 21.55,/? < .0001. The aerobic group increased its treadmill time by 1.5 min, F(l, 22) = 60.31, /? < .0001, whereas the treadmill time for the strength group did not change, F(l, 21) = 0.54, p < .49. The univariate effects for peak VO2 revealed significant effects for group, F(l, 39) = 5.34,/? < .03, and time, F(l, 42) = 16.43, p < .0002, and a significant Group x Time interaction, F(l, 39) = 21.59,/? < .0001. The aerobic group increased its peak VO2 by almost 20%, F(l, 21) = 35.22, p < .0001, whereas the peak VO2 for the strength group did not change. Thus, the two exercise groups experienced different patterns of change. As expected, participants in the aerobic 2
Several subjects attended extra classes.
388
BLUMENTHAL ET AL. TABLE 3 Changes in Aerobic Fitness for Strength and Aerobic Groups Exercise Group Aerobicb
Strenth* Time 1 Measure
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Resting HR (bpm) HR at 5 METs (bpm) Peak VO2 (ml/kg/min) Time on treadmill (min)
Time 2
Time 1
Time 2
M
SD
M
SD
M
SD
M
SD
79 134.6 26.1 8.8
10 11.0 4.5 1.1
76 127.5 26.0 8.9
9 11.0 4.6 1.3
75 131.4 26.7 9.6
9 11.8 4.2 1.2
68* 124.1 31.6** 11.1**
9 13.8 5.9 1.7
a
« = 22. bn = 24. *p < .001. **p < .0001.
group increased their aerobic fitness, whereas participants in the strength group did not improve their aerobic fitness. Premenopausal and postmenopausal women experienced comparable improvements in aerobic capacity. In addition, subjects in both groups lost a comparable amount of body weight (mean weight at Time 1 = 146 ± 19 lb, mean weight at Time 2 = 145 ± 19 lb). Responses to Behavioral Stressors Speech. The mean values for the cardiovascular and neuroendocrine responses are presented in Table 4. To assess the effects of exercise training on cardiovascular and neuroendocrine responses to the speaking task, a series of ANCOVAs was performed for HR, SBP, DBP, epinephrine, and norepinephrine with task level at Time 1 and age as covariates. Only HR was significant, with subjects in the aerobic group having lower levels than those of subjects in the strength group (82 vs. 89 bpm, p < .05). To assess reactivity, ANCOVAs with age, resting values at Time 1 and Time 2, and task levels at Time 1 as covariates did not reveal any significant group effects or Group x Menopausal Status interactions for BP, epinephrine, or norepinephrine. Cold. A series of ANCOVAs was employed to evaluate the effects of the two exercise conditions on responses to the cold challenge. Results of the ANCOVA revealed a significant Group x Menopausal Status interaction for DBP, F(2, 40) = 5.99, p < .006, and SBP, F(2, 40) = 6.70, p < .004. For the postmenopausal women, participants in the aerobic group had lower DBP (LSMs = 77 vs. 83 mm Hg, p < .03) and SBP (LSMs = 126 vs. 135mmHg,/7 < .04) than participants in the strength group. Unexpectedly, however, premenopausal women showed the opposite pattern: Participants in the strength group had lower DBP (LSMs = 74 vs. 80 mm Hg, p < .04) and lower SBP (LSMs = 121 vs. 132 mm Hg,/? < .02). There were no group differences in neuroendocrine levels during the cold challenge after exercise training. Significant Group X Menopausal Status effects were found for DBP, F(2, 38) = 3.65, p < .04, and SBP, F(2, 38) = 3.58, p < .04, reactivity. Post hoc tests revealed that postmenopausal women in the aerobic group had lower DBP reactivity than postmenopausal women in the strength group
(LSMs = 75.9 vs. 82.1 mm Hg, p < .03) and tended to have lower SBP reactivity (LSMs = 124.7 vs. 133.1 mm Hg, p < .06). There were no differences in reactivity among the premenopausal women in the aerobic and strength groups (LSMs: SBP = 131.5 vs. 124.5 mm Hg, DBP = 79.1 vs. 75.9 mm Hg). DISCUSSION This study investigated the potential influence of reproductive hormones and aerobic exercise training on psychophysiological stress responses. Results showed that premenopausal and postmenopausal women generally exhibited comparable cardiovascular stress responses prior to exercise training. On the other hand, postmenopausal women displayed lower resting levels and greater epinephrine reactivity to the speaking task. The results of the study provide partial support for the results reported from the only other study of psychophysiological responses of similar-age premenopausal and postmenopausal women. Saab et al. (1989) reported that postmenopausal women had higher HR, SBP, and epinephrine levels during speech performance than premenopausal women did. In terms of aerobic training, the women in our study achieved aerobic capacity improvements comparable to those of men who have undergone identical exercise training protocols (Blumenthal, Emery et al., 1988; Blumenthal et al., 1990). Moreover, premenopausal and postmenopausal women experienced similar improvements in peak VO2. Thus, our results indicate that reproductive hormones do not appear to influence the magnitude of cardiopulmonary training effects in response to aerobic exercise. When the effects of exercise training on stress reactivity were considered, results provided only partial support for our previous findings (e.g., Blumenthal et al., 1990). Although women in the aerobic group had HR levels lower than those of the strength group during the speech task, this advantage became nonsignificant when resting levels at Time 1 and Time 2 were added as covariates. This pattern suggests that HR levels during stress —but not reactivity—may be reduced by aerobic exercise training. With respect to the cold challenge, an interesting and somewhat inconsistent pattern emerged. Aerobic exercise for the postmenopausal women, but not for the premenopausal
TABLE 4 Cardiovascular and Neuroendocrine Values at Baseline (Rest 1), Speech, Rest 2, Cold, and Rest 3 for Premenopausal and Postmenopausal Women Before (Time 1) and After (Time 2) Aerobic or Strength Training Menopausal Status Premenopausal
Postmenopausal Strength b
Aerobic? Measure HR (bpm) Rest 1 Speech
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Rest 2 Cold Rest 3 SBP (mm Hg) Rest 1 Speech Rest 2 Cold Rest 3 DBP (mm Hg) Rest 1 Speech Rest 2 Cold Rest 3 Epinephrine (pg/ml) Rest 1 Speech Rest 2 Cold Rest 3 Norepinephrine (pg/ml) Rest 1 Speech Rest 2 Cold Rest 3
Time 1
Time 2
Strength b
Aerobic*
Time 1
Time 2
Time 1
Time 2
Time 1
Time 2
75 (8) 98 (12) 77 (7) 75 (6) 75 (6)
70 (8) 87 (9) 68 (6) 68 (6) 68 (7)
73 (5) 94 (12) 74 (5) 74 (6) 72 (5)
72 (6) 91 (10) 72 (6) 71 (9) 71 (6)
73 (10) 84 (10) 73 (10) 73 (11) 71 (9)
69 (10) 78 (8) 68 (10) 69 (9) 68 (10)
74 (8) 95 (11) 75 (8) 73 (8) 72 (6)
73 (7) 88 (13) 72 (6) 69 (9) 69 (6)
115 (15) 155 (18) 125 (14) 135 (21) 118 (11)
115 (11) 149 (17) 121 (12) 134 (19) 117 (13)
107 (10) 141 (15) 116 (11) 121 (15) 110 (7)
102 (4) 134 (15) 109 (5) 114 (10) 105 (5)
117 (11) 146 (14) 121 (13) 140 (16) 121 (15)
115 (11) 140 (14) 122 (12) 130 (13) 117 (12)
118 (11) 156 (13) 129 (11) 133 (12) 121 (9)
120 (9) 147 (14) 124 (9) 135 (12) 120 (10)
72 (12) 92 (14) 76 (12) 83 (14) 74 (10)
73 (10) 89 (13) 74 (11) 85 (15) 72 (10)
64 (5) 82 (7) 66 (5) 72 (9) 64 (6)
61 (3) 79 (9) 62 (4) 69 (8) 62 (3)
70 (9) 87 (10) 71 (9) 82 (9) 71 (9)
69 (7) 85 (11) 72 (8) 78 (9) 71 (7)
71 (11) 94 (12) 73 (11) 79 (10) 72 (11)
72 (9) 88 (12) 72 (8) 82 (10) 72 (10)
56 (41) 121 (68) 65 (41) 59 (35) 49 (37)
35 (23) 66 (42) 35 (14) 49 (30) 52 (27)
30 (18) 93 (55) 40 (21) 49 (33) 49 (45)
54 (45) 66 (40) 60 (23) 47 (35) 44 (41)
41 (40) 99 (101) 40 (31) 48 (38) 39 (33)
24 (18) 74 (68) 32 (24) 33 (24) 30 (24)
30 (22) 102 (57) 44 (19) 44 (20) 47 (21)
33 (23) 96 (69) 36 (21) 51 (21) 37 (17)
329 (158) 461 (182) 343 (171) 462 (258) 429 (256)
377 (225) 497 (264) 359 (148) 490 (253) 402 (177)
280 (131) 378 (171) 251 (115) 318 (124) 284 (95)
365 (157) 401 (211) 233 (93) 303 (123) 307 (133)
258 (127) 385 (110) 253 (76) 395 (113) 349 (103)
236 (85) 376 (117) 221 (52) 327 (97) 298 (111)
330 (116) 441 (161) 317 (74) 398 (163) 355 (117)
289 (99) 458 (259) 310 (135) 486 (312) 328 (193)
Note. Means are unadjusted for age; standard deviations are in parentheses. a n = 12. bn = 11.
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BLUMENTHAL ET AL.
women, was associated with significantly lower BP levels and an attenuation of BP reactivity compared to strength training. However, premenopausal women in the strength group (compared to the aerobic group) exhibited lower BP levels. We have no explanation for this finding. Unfortunately, one limitation of our study was that we did not include a nonexercise control group. Consequently, we were unable to distinguish the effects of any exercise (aerobic or strength training) from the effects of no exercise at all. There are several important differences between the present study and our previous work — involving the selection of stressors and the nature of the subject population. In both our previous studies, we employed a moderate stressor — mental arithmetic — that generally elicited a 10-bpm increase in HR, a 10- to 15-mm Hg increase in SBP, and a 5- to 10-mm Hg increase in DBP. In contrast, the public speaking task was twice as potent; HR increased more than 20 bpm, and SBP and DBP increased by almost 40 mm Hg and 20 mm Hg, respectively. It is possible that aerobic exercise may attenuate psychophysiologic responses to low to moderate stressors but not to more intense stressors. The present study was also the first to employ a cold challenge, which yielded inconsistent results. In addition, in our previous work we studied Type A men; in the present study, women were not preselected on the basis of their being Type A. Differences in the nature of the stressors and in certain individual characteristics may have contributed to the different pattern of results. A final factor that may be relevant is the fitness levels of study subjects. Post hoc analyses by Holmes and McGilley (1987) revealed that aerobic exercise reduced HR levels during a memory task among a subgroup of unfit young (17- to 20-year-old) women but not among more fit women. It is difficult to compare their results to ours, however, because Holmes and McGilley only estimated levels of aerobic fitness, and we measured aerobic power directly with expired gas analyses. However, it is unlikely that different levels of fitness were responsible for the inconsistency of the present findings and those of our previous work with men, as the women in this study were all sedentary, with an average aerobic capacity— less than 8 METs — that was less than that obtained for men of similar age. In conclusion, our findings indicate that a program of aerobic exercise may serve to reduce levels of cardiovascular response to behavioral stressors among middle-aged women. However, reproductive hormones, along with the nature of the stressor, may affect this response. Future research should attempt to clarify the role of aerobic exercise in reducing stress responses, including identifying individual-difference factors (e.g., Type A vs. Type B, fit vs. unfit, or young vs. old individuals), task characteristics (e.g., mild stressors vs. moderate stressors, alpha- vs. beta-adrenergic tasks), and exercise training regimens (e.g., aerobic vs. non-aerobic exercise, moderate- vs. high-intensity exercise) that may account for some of the inconsistencies in the results. ACKNOWLEDGMENTS Manuscript preparation was supported by National Institutes of Health Grants HL 30675 and AG 04238 and by a grant
from the John D. and Catherine T. MacArthur Network on the Determinants and Consequences of Health-Promoting and Health-Damaging Behavior. We thank Margo Walsh-Riddle, Sally Schnitz, and Robin Pomeroy for their technical assistance and Janet Ivey for her secretarial assistance. REFERENCES Blumenthal, J. A., Emery, C. F., Walsh, M. A., Cox, D. R., Kuhn, C. M., Williams, R. B., & Williams, R. S. (1988). Exercise training in healthy Type A middle-aged men: Effects on behavioral and cardiovascular responses. Psychosomatic Medicine, 50, 418-433. Blumenthal, J. A., Fredrikson, M., Kuhn, C. M., Ulmer, R. L., Walsh-Riddle, M., & Appelbaum, M. (1990). Aerobic exercise reduces levels of cardiovascular and sympathoadrenal responses to mental stress in subjects without prior evidence of myocardial ischemia. American Journal of Cardiology, 65, 93-98. Blumenthal, J. A., Rejeski, W. J., Walsh-Riddle, M., Emery, C. F., Miller, H., Roark, S., Ribisl, P. M., Morris, P. B., Brubaker, P., & Williams, R. S. (1988). Comparison of high- and low-intensity exercise training early after acute myocardial infarction. American Journal of Cardiology, 61, 26-30. Borg, G. (1982). Psychophysiological bases of perceived exertion. Medicine and Science in Sports and Exercise, 14, 377-387. Collins, A., & Frankenhaueser, M. (1978). Stress responses in male and female engineering students. Journal of Human Stress, 4, 43-48. Crews, D. J., & Landers, D. M. (1987). A meta-analytic review of aerobic fitness and reactivity to psychosocial stressors. Medicine and Science in Sports and Exercise, 19, S114-S120. Frankenhaueser, M. (1983). The sympathetic-adrenal and pituitaryadrenal response to challenge: Comparison between the sexes. In T. M. Dembroski, T. H. Schmidt, & G. Blumchen (Eds.), Biobehavioral bases of coronary heart disease (pp. 91-105). Basel, Switzerland: Karger. Frankenhaueser, M., Dunne, E., & Lundberg, U. (1976). Sex differences in sympathetic-adrenal medullary reactions induced by different stressors. Psychopharmacology, 47, 1-5. Frankenhaueser, M., Lundberg, U., & Forsman, L. (1980). Dissociation between sympathetic-adrenal and pituitary-adrenal responses to an achievement situation characterized by high controllability: Comparison between Type A and Type B males and females. Biological Psychology, 10, 79-91. Holmes, D. S., & McGilley, B. M. (1987). Influence of a brief aerobic training program on heart rate and subjective response to a psychologic stressor. Psychosomatic Medicine, 49, 366-374. Johansson, G. (1972). Sex differences in the catecholamine output of children. Acta Physiologica Scandinavica, 86, 569-572. Johansson, G., & Post, B. (1973). Catecholamine output in school children as related to performance and adjustment. Scandinavian Journal of Psychology, 14, 20-28. Kilts, C. D., Gooch, M. D., &Knopes, K. D. (1984). Quantitation of plasma catecholamines by on-line trace enrichment high performance liquid chromatography with electrochemical detection. Journal of Neuroscience Methods, 11, 257-273. Krantz, D. S., & Manuck, S. B. (1984). Acute psychophysiologic reactivity and risk of cardiovascular disease: A review and methodologic critique. Psychological Bulletin, 96, 435-464. Lundberg, U. (1983). Sex differences in behavior pattern and catecholamine and cortisol excretion in 3-6 year old day-care children. Biological Psychology, 16, 109-117. Manuck, S. B., & Polefrone, J. M. (1987). Psychophysiologic reaptivity in women. In E. D. Eaker, B. Packard, N. C. Wenger, T. B»
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