The Role of Exercise in the Primary and Secondary Prevention of Coronary Artery Disease

Over the past 30 years, mortality rates from coronary artery disease (CAD) have decreased by more than 30% in the United States. However, CAD remains the major public health problem in this country. There is now substantial evidence linking exercise training to a reduced risk for CAD and for mortality after myocardial infarction. The actual mechanism by which physical activity aids in reducing the risk for developing or dying from CAD has still to be elucidated. Several highly plausible mechanisms have been postulated, including decreased myocardial oxygen demand, increased myocardial oxygen supply, reduced propensity toward ventricular arrhythmias, reduced platelet aggregation, increased plasma fibrinolytic activity, and modification of multiple CAD risk factors. Irrespective of the precise mechanism, it now appears that lower levels of physical activity are needed to reduce the risk for CAD than are needed to optimize cardiorespiratory fitness. In this regard, we recommend that the type, frequency, intensity, and duration of exercise training be modulated to achieve a weekly energy expenditure of between 14 and 20 kilocalories per kilogram of body weight. Although aerobic activities should be emphasized, muscle strengthening and flexibility exercises should also be incorporated into the training program in order to promote musculoskeletal health

Effect of Macronutrient Composition of An Energy-Restrictive Diet on Maximal Physical Performance

Effect of macronutrient composition of an energy-restrictive diet on maximal physical performance. Med. Sci. Sports Exerc., Vol. 24, No. 7, pp. 814–818,1992. Thirty-six sedentary, mildly obese (30–40% fat), premenopausal women (29–49 yr) were randomly assigned to one of two dietary regimens for an 8-wk double-blind, parallel study of the effect of moderate caloric restriction and macronutrient variation on maximal physical performance. Group 1 (N = 19) consumed 4186 kJ·d-1 (1000 kcal·d-1) with a diet composition of 40% fat, 40% carbohydrate (CHO), and 20% protein. Group 2 (N = 17) also consumed 4186 kJ·d-1 but varied the percent kilojoules to 20% fat, 60% CHO, and 20% protein. Maximal aerobic power was measured using a modified Balke protocol, strength was assessed using isotonic bench and leg press machines and a Cybex 340 isoki-netic device during knee flexion and extension, and muscular endurance was taken as the number of sit-ups performed in 1 min. Pre- to post-testing revealed significant (P ≤ 0.05) reductions in body weight (group 1, −7.4 kg; group 2, −6.5 kg) within both groups. No significant changes were seen in maximal aerobic power within both groups. Strength measures for both groups showed a trend toward reduction but statistical significance was only evident in right knee extension for group 1 and left knee extension for group 2 (P ≤ 0.05). Sit-up number increased nonsignificantly for both groups. Between group differences were not found in any body weight, body composition, or physical performance index. We therefore conclude that in mildly obese women, maximal exercise performance is relatively unimpaired after 8 wk of caloric restriction with either of two diets differing moderately in their macronutrient content

Women Walking for Health and Fitness: How Much Is Enough?

Objective. —We studied whether the quantity and quality of walking necessary to decrease the risk of cardiovascular disease among women differed substantially from that required to improve cardiorespiratory fitness. Design. —A randomized, controlled, dose-response clinical trial with a follow-up of 24 weeks. Setting. —A private, nonprofit biomedical research facility. Participants. —One hundred two sedentary premenopausal women, 20 to 40 years of age, were randomized to one of four treatment groups; 59 completed the study (16 aerobic walkers [8.0-km/h group], 12 brisk walkers [6.4-km/h group], 18 strollers [4.8-km/h group], and 13 sedentary controls). Eighty-one percent were white, 17% black, and 2% Hispanic. Intervention. —Intervention groups walked 4.8 km per day, 5 days per week at 8.0 km/h, 6.4 km/h, or 4.8 km/h on a tartan-surfaced, 1.6-km track for 24 weeks. Main Outcome Measures. —Fitness (determined by maximal oxygen uptake) and cardiovascular risk factors (determined by resting blood pressure and serum lipid and lipoprotein levels). Results. —As compared with controls, maximal oxygen uptake increased significantly (P\u3c.0001) and in a dose-response manner (aerobic walkers\u3ebrisk walkers\u3estrollers). In contrast, high-density lipoprotein cholesterol concentrations were not dose related and increased significantly (P\u3c.05) and to the same extent among women who experienced considerable improvements in their physical fitness (8.0-km/h group, +0.08 mmol/L) and those who had only minimal improvements in fitness (4.8-km/h group, +0.08 mmol/L). High-density lipoprotein cholesterol also increased among the 6.4-km/h group, but did not attain statistical significance (+0.06 mmol/L; P=.06). Dietary patterns revealed no significant differences among groups. Conclusion. —Thus, we conclude that vigorous exercise is not necessary for women to obtain meaningful improvements in their lipoprotein profile. Walking at intensities that do not have a major impact on cardiorespiratory fitness may nonetheless produce equally favorable changes in the cardiovascular risk profile.(JAMA. 1991;266:3295-3299

Exercise and Mild Essential Hypertension

Chronic essential hypertension is a major public health problem afflicting an estimated 15 to 30% of persons from most Western industrialised countries. Persons with mild hypertension (diastolic blood pressure between 90 and 104mm Hg and/or systolic blood pressure between 140 and 159mm Hg) represent the overwhelming majority of hypertensive individuals in the general population. The achievement of long term blood pressure control in these individuals is of central strategic concern in the prevention of hypertension-related morbidity and mortality. Epidemiological studies suggest that regular participation in physical activity may be beneficial in preventing hypertension. The findings of epidemiological studies are supported by a recent meta-analysis of 25 longitudinal aerobic training studies, in which the average sample-size-weighted reductions in resting systolic and diastolic blood pressures were 10.8mm Hg and 8.2mm Hg, respectively. Moreover, preliminary analyses from our centre suggest that cardiorespiratory fitness and, by inference, aerobic exercise training may be of benefit in reducing mortality rates in hypertensive patients. When compiling an exercise prescription with the intention of reducing an elevated blood pressure and attenuating the risk for coronary artery disease, several factors must be considered in order to optimise the likelihood of a safe and effective response. Specifically, the 5 basic components of the exercise prescription for patients with mild hypertension are safety aspects, the type of exercise to be performed, and the frequency, intensity and duration of exercise training. For those patients who require pharmacotherapy, the interaction between the specific antihypertensive agent and exercise responses must also be considered. We recommend that aerobic exercise training be performed at an intensity corresponding to 60 to 85% of the maximal heart rate and that the duration and frequency be modulated to achieve a weekly energy expenditure of between 14 and 20 kcal/kg of body weight

Musculoskeletal Strength and Serum Lipid Levels in Men and Women

Musculoskeletal strength and serum lipid levels in men and women. Med. Sci. Sports Exerc., Vol. 24, No. 10, pp. 1080–1087, 1992. There currently is inconsistent information regarding the role that musculoskeletal strength (one component of musculoskeletal fitness) may have in lipid and lipoprotein metabolism, and consequently the risk of cardiovascular disease. Results of existing studies have been conflicting and have been influenced by several weaknesses. We provide cross-sectional analyses of the relation between muscular strength and serum lipid and lipoprotein status in a group of 1,193 women and 5,460 men. The large proportion of patients were not involved in formal weight training. As part of a preventive medical examination, patients were tested for maximal upper and lower body strength (one repetition maximum (1RM) bench and leg press). Fasting serum total cholesterol (TC), low-density lipoprotein cholesterol (LDLC), triglyceride (TG), and high density lipoprotein (HDLC) were evaluated for their relation to muscle strength, after adjusting for simultaneous associations with age, body composition, and cardiovascular fitness. Results showed no association between muscular strength and serum TC or LDLC for either men or women and a direct association between upper and lower body strength and TG in men. The direct association between strength and TG in women was not significant. A statistically significant inverse association was seen between muscular strength and HDLC in men only. These data suggest no beneficial effect, and perhaps an adverse association of muscular strength on lipid and lipoprotein status