(Chest. 2004;126:1026-1031.)
© 2004
American College of Chest Physicians
Exercise Training Improves Overall Physical Fitness and Quality of Life in Older Women With Coronary Artery Disease*
Chihya Hung, MSc;
Bill Daub, MSc;
Bill Black, MD;
Robert Welsh, MD;
Arthur Quinney, PhD and
Mark Haykowsky, PhD
* From the Faculty of Rehabilitation Medicine (Dr. Haykowski and Mrs. Hung), Northern Alberta Cardiac Rehabilitation Program (Mr. Daub and Dr. Black), Division of Cardiology, Faculty of Medicine (Dr. Welsh), and Faculty of Physical Education and Recreation (Dr. Quinney), University of Alberta, Edmonton, Alberta, Canada.
Correspondence to: Mark Haykowsky, PhD, Faculty of Rehabilitation Medicine, 2–50 Corbett Hall, University of Alberta, Edmonton, Alberta, Canada, T6G 2G4, e-mail: mark.haykowsky{at}ualberta.ca
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Abstract
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Background: Older women with coronary artery disease (CAD) have reduced peak aerobic power (
O2peak), muscle strength, and quality of life (QOL). Exercise interventions that can improve O2peak and muscle strength may also result in an improvement in QOL. This study compared the effect of aerobic training (AT) or combined aerobic and strength training (COMT) on O2peak, distance walked in 6 min, upper- and lower-extremity maximal strength, and QOL in 18 women (age range, 60 to 80 years) with documented CAD.
Methods: After baseline testing, subjects were randomly assigned to AT (treadmill and cycle exercise, n = 9) or COMT (treadmill and cycle exercise plus upper- and lower-extremity strength training, n = 9), and each group exercised 3 d/wk for 8 weeks.
Results: Both AT and COMT resulted in a similar increase in O2peak, distance walked in 6 min, lower-extremity strength, and emotional and global QOL. COMT improved upper-extremity strength, and physical and social QOL, which was unchanged after AT.
Conclusions: Older women with CAD should perform aerobic and strength training to attain optimal improvements in overall physical fitness and QOL.
Key Words: aerobic training • coronary artery disease • strength training
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Introduction
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Exercise training is an important intervention that can reverse the decline in peak aerobic power (O2peak)1234 and muscle strength5678 that occurs in older individuals with coronary artery disease (CAD). The improvement in O2peak has prognostic implications, as Kavanagh et al9 recently reported that a 1 mL/kg/min increase in O2peak was associated with a 10% reduction in cardiac mortality in older women with CAD. A limitation of previous cardiac rehabilitation exercise studies410 was the exclusion of older women with CAD as study participants. Older women with CAD may have the most to gain from participating in an exercise rehabilitation program because they have a O2peak that is 26 to 45% lower than age-matched healthy sedentary or active women9111213 (Fig 1
). Furthermore, older women with CAD have a O2peak that is at or below the threshold level required for independent living (Fig 1). Exercise interventions that can increase O2peak and muscle strength may result in a concomitant improvement in overall quality of life (QOL) in older women with CAD. The purpose of this investigation was to examine the effects of 8 weeks of aerobic training (AT) or combined aerobic and strength training (COMT) on O2peak, distance walked in 6 min, upper- and lower-extremity maximal strength, and QOL in older women with CAD. We hypothesized that COMT would result in a greater increase in overall physical fitness and QOL compared to AT.
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Materials and Methods
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Study Subjects
The subjects consisted of 21 women (age range, 60 to 80 years) who recently had a myocardial infarction and were referred to the Northern Alberta Cardiac Rehabilitation program. Ethics approval was obtained from the University Health Research Ethics Board, and informed consent was obtained prior to study participation.
Incremental Exercise Test With Expired Gas Analysis
The incremental exercise test was performed using the Bruce or modified Bruce protocols. Expired gases were collected and analyzed using a computerized metabolic system (ParvoMedics; Sandy, UT), and the highest oxygen uptake obtained over a 1-min period was used as the O2peak score. A continuous 12-lead ECG was used during the test, while BP was obtained every 3 min.
Six-Minute Walk Test
The 6-min walk test was performed in accordance with the American Thoracic Society guidelines.14
Upper- and Lower-Extremity Maximal Strength Testing
Subjects were shown the correct technique required to perform eight (chest press, shoulder press, vertical row, triceps extension, biceps curl, latissimus dorsi pull down, leg extension, and leg curl) strength exercises, after which time they were given an opportunity to perform each exercise. The heaviest weight lifted once while adhering to strict technique was used as the one-repetition maximum (1RM). The 1RM test was repeated a second time within a 1-week period, and the highest score of the 2 days was used as the baseline score.
Health-Related QOL
Health-related QOL was assessed using the MacNew heart disease health-related QOL instrument,15 which measures the physical, emotional, social, and global domains of well-being.
Randomization and Interventions
After the baseline testing, subjects were randomly assigned to 8 weeks of AT or COMT. AT was performed 3 d/wk at 70 to 85% of peak heart rate for 30 min per session using treadmill or cycle ergometers. The COMT subjects performed the same aerobic program as the AT subjects. They also performed one to two sets of 8 to 10 repetitions of the previously described strength-training exercises. The initial intensity was set at 55% of 1RM, and increased by 2.5% every week.
Statistical Methods
Statistical analysis was performed with a two-way, repeated-measures analysis of variance. If a significant effect was found, then a Neuman-Kuels post hoc test was performed. The 
level was set a priori at p < 0.05. Data are presented as mean ± SD.
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Results
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Three subjects did not complete the investigation. One AT subject completed < 80% of the required exercise sessions, while another AT subject dropped out of the study due to worsening of asthma not related to participating in the study. One COMT subject dropped out of the study due to family reasons. Thus, nine AT subjects (mean age, 70 ± 6 years) and nine COMT subjects (mean age, 71 ± 7 years) completed the study, with adherence rates of 96% and 98%, respectively.
Baseline Analysis
At baseline, the social QOL of the AT subjects was significantly greater than that of COMT subjects (Table 1
). No significant difference was found between the groups for any other baseline measure (Table 1).
Effects of Exercise Training on O2peak and Distance Walked in 6 min
Both AT and COMT resulted in a similar increase in peak exercise ventilation, oxygen pulse, O2peak, and distance walked in 6 min (Fig 2
). No significant change in peak heart rate was found after training (pretraining, 115 ± 19 beats/min, vs posttraining, 119 ± 20 beats/min).
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Figure 2. Effects of exercise training on O2peak, peak oxygen pulse (O2 Pulse peak), ventilation (VEpeak), and distance walked in 6 min (6 MWD). *p < 0.05 vs before training (Pre). Post = after exercise training.
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Effects of Exercise Training on Upper- and Lower-Extremity Strength
AT and COMT resulted in a similar increase in leg curl and leg-extension 1RMs (Fig 3
). Vertical row, shoulder press, chest press, latissimus dorsi pull down, biceps curl, and triceps push down 1RMs were significantly greater after 8 weeks of COMT and were unchanged with AT (Table 2
).
Effects of Exercise Training on QOL
Both AT and COMT resulted in a similar increase in emotional and global QOL (Table 3
). Physical and social QOL were significantly greater after 8-weeks of COMT, and were unchanged with AT (Table 3).
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Discussion
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The main finding of this investigation was that AT or COMT were equally effective in improving O2peak, distance walked in 6 min, lower-extremity strength, and emotional and global QOL in older women with CAD. A second finding was that upper-extremity strength and physical and social QOL were significantly greater after 8 weeks of COMT, and were unchanged with AT.
Improvement in O2peak With Exercise Training
Few studies have examined the effect that exercise training has on altering O2peak in older women with CAD. Ades et al34 and others121617 have found that 12 to 26 weeks of AT resulted in a 5 to 30% increase in O2peak in older women (age range, 53 to 82 years) with CAD. We found that 8 weeks of AT or COMT resulted in a 12% increase in O2peak. This improvement is due to an increase in stroke volume and/or arteriovenous oxygen difference, as the oxygen pulse during peak exercise was significantly higher after training (Fig 2). Ades et al3 and Kirwin et al12 found that the heightened O2peak is secondary to an increase in arteriovenous oxygen difference, as 12 to 26 weeks of AT did not alter submaximal or maximal stroke volume or cardiac output in older women with CAD. Thus, not unlike that found in healthy older women,18 the increase in O2peak associated with exercise training in older women with CAD appears to be due to an increase in peak arteriovenous oxygen difference.
Effects of Exercise Training on Aerobic Endurance
Previous studies have found that strength training alone67 or combined with AT19 was associated with a 11 to 20% increase in distance walked in 6 min in older women with CAD or heart failure. We found that 8 weeks of AT or COMT was associated with a 10% increase in the distance walked in 6 min. Thus, the heightened O2peak that occurs with AT or COMT also increases aerobic endurance, which allows older women with CAD to increase the distance that they can walk during a 6-min period.
Effects of Exercise Training on Maximal Strength and QOL
An unexpected finding in this investigation was that 8 weeks of AT or COMT resulted in a significant improvement in lower-extremity maximal muscular strength (Fig 3). However, the absolute change in leg extension (AT, + 3.3 kg, vs COMT, + 6.6 kg) and leg curl (AT, + 3.6 kg, vs COMT, + 7.1 kg) strength was twofold greater after COMT compared to AT. Also, 8 weeks of COMT resulted in a 15 to 29% increase in upper-extremity strength, which remained unchanged with AT (Table 2). These results confirm the findings by Ades et al7 and others,568 who found that 3 to 6 months of strength or COMT was associated with an increase in upper-extremity (18 to 29%) and lower-extremity (23 to 68%) strength in older women with CAD or heart failure. The consequence of the heightened muscle strength is that it is associated with an increased ability to perform activities of daily living,78 resulting in an improvement in QOL.1 Consistent with this hypothesis, we found that the subjects who performed COMT had a greater absolute change in emotional, physical, social, and global QOL compared to the AT subjects. This is an important finding, because older women with CAD have been shown to have reduced social support,20 greater emotional difficulties,21 and impaired functional capacity (Fig 1). Moreover, this finding confirms and extend previous cardiac exercise rehabilitation intervention studies2223 demonstrating that in order to attain optimal gains in overall fitness and QOL, older women with CAD should be encouraged to perform an exercise regimen that incorporates both strength training and AT.
Study Limitations
A limitation of our study is the small sample size. However, older women with CAD are less likely to be referred to or adhere to a cardiac exercise rehabilitation program.424 This is the first prospective study to examine the effects of AT or COMT on O2peak, distance walked in 6 min, upper- and lower-extremity maximal strength, and QOL in women with CAD in their seventh decade of life. Moreover, the improvement in overall physical fitness may make the difference between living independently vs becoming a resident of a seniors’ home in the near future after having a myocardial infarction.
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Conclusion
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Eight weeks of AT or COMT were equally effective in improving O2peak, distance walked in 6 min, lower-extremity strength, and emotional and global QOL in older women with CAD. Moreover, COMT resulted in a significant increase in upper-extremity strength, and physical and social QOL, which remain unchanged after AT. Thus, older women who participate in a cardiac exercise rehabilitation program should perform AT and strength training to attain optimal improvements in overall physical fitness and QOL.
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Footnotes
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Abbreviations: AT = aerobic training; CAD = coronary artery disease; COMT = combined aerobic and strength training; QOL = quality of life; O2peak = peak aerobic power; 1RM = one-repetition maximum
Received for publication February 9, 2004.
Accepted for publication May 12, 2004.
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References
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Abstract
Introduction
