Abstract
PURPOSE: Increasing caloric expenditure through physical activity is associated with reduced mortality. On the basis of observational studies, previous authors have suggested that at least 1000 kcal per week and possibly 1500 kcal per week of physical activity is necessary for health benefits. The authors have previously reported that patients in maintenance cardiac rehabilitation accumulate approximately 230 kcal per exercise session, suggesting that additional activity outside of cardiac rehabilitation is needed to achieve the goal of 1500 kcal per week. The authors estimated the amount of energy expenditure performed each week by patients in cardiac rehabilitation during both program participation and leisure time.
METHODS: For this study, 104 patients enrolled in a supervised maintenance cardiac rehabilitation program at both tertiary care and community settings for at least 6 months completed a self-administered physical activity questionnaire. Energy expenditure in cardiac rehabilitation and leisure time activity was measured in kilocalories. Total caloric expenditure was determined by adding up the number of kilocalories expended by the patients each week climbing stairs, walking, participating in cardiac rehabilitation, and engaging in sports.
RESULTS: Patients in cardiac rehabilitation expended weekly, on the average, 1504 +/- 830 kcal in physical activity, 830 +/- 428 kcal in cardiac rehabilitation, and 675 +/- 659 kcal in leisure time activity. There was a significant difference in caloric expenditure between men and women, between those with a body mass index (BMI) less than 30 and those with a BMI of 30 or more, and between those younger than 70 years and those 70 years or older. There was no difference between races. Whereas 43% of the patients accumulated 1500 kcal, 57% did not.
CONCLUSIONS: The findings showed that 72% of the patients in cardiac rehabilitation accumulated at least 1000 kcal of energy expenditure per week and met public health guidelines. Also, 43% of the patients in cardiac rehabilitation accumulated more than 1500 kcal of energy expenditure per week, a level identified as necessary to reduce all-cause mortality. Women of either race, patients with a BMI of 30 or more, and patients age 70 years or older are the groups least likely to achieve 1500 kcal of energy expenditure per week. The authors recommend incorporating weekly kilocalories of energy expenditure in the exercise prescription of patients to ensure achievement of maximum health benefits.
Current public health recommendations suggest that on most days of the week, adults accumulate at least 30 minutes of endurance type physical activity characterized by at least a moderate intensity. 1,2 This results in a volume of exercise approximating 1000 kcal per week. On the basis of observational studies, investigators suggest that larger volumes of physical activity are necessary to reduce all-cause mortality (>=1500 kcal/week) 3-5 and reduce cardiovascular mortality (>=2000 kcal/week) 7,8 in patients without heart disease. Hambrecht et al 9 reported partial reversal of coronary artery lesions with even higher levels of energy expenditure (>=2200 kcal/week) in patients with known coronary artery disease.
For patients participating in maintenance cardiac rehabilitation and secondary prevention programs subsequent to an initial myocardial infarction or coronary revascularization, caloric expenditure has been measured at 230 to 270 kcal per 45-minute session. 9-10 Because most patients participate in cardiac rehabilitation three times per week, they likely would fall well short of the 1000 kcal per week threshold needed for health benefits. Although it is recommended to patients in cardiac rehabilitation programs that they exercise on the days when they are not in cardiac rehabilitation, it generally is thought that few do additional exercise outside of cardiac rehabilitation.
Therefore, weekly kilocalories of expenditure was assessed among patients in cardiac rehabilitation using a modification of the Paffenbarger Physical Activity Questionnaire. 6-11 It was hypothesized that patients in cardiac rehabilitation were not performing additional leisure time physical activity when not in cardiac rehabilitation, and that their weekly caloric expenditure would be less than 1000 kcal/week. Additionally, current data on leisure time physical activity and health involve mostly men. Thus, it was decided to study women in this context as well.