The exercise-induced oxidative stress paradox: the effects of physical exercise training.

BACKGROUND: Although physical exercise training is highly recommended, physical exercise causes oxidative stress, which is potentially injurious. This study evaluates this 'exercise paradox' by evaluating the effect of physical exercise on exercise-induced lipid peroxidation. METHODS: Measurement of lipid peroxidation (ie, expired ethane and pentane and plasma malondealdehyde) taken during cardiopulmonary exercise stress testing were compared between a group of 10 cardiac patients who underwent physical exercise training in a cardiac rehabilitation setting and a group of 10 nonexercising cardiac patients. RESULTS: Our findings indicate that physical exercise training increased physical work capacity without a concomitant increase in expired markers of lipid peroxidation (ethane and pentane) and decreased malondealdehyde levels. CONCLUSIONS: Because physical exercise-trained people can perform more intense physical work with less oxidative stress, we conclude that physical exercise training can reduce potential chronic health effects associated with daily activities by contributing to an overall reduction in exercise-induced free radical production.

A controlled trial of exercise rehabilitation after heart transplantation.

BACKGROUND: In patients who have received a cardiac transplant, the denervated donor heart responds abnormally to exercise and exercise tolerance is reduced. The role of physical exercise in the treatment of patients who have undergone cardiac transplantation has not been determined. We assessed the effects of training on the capacity for exercise early after cardiac transplantation. METHODS: Twenty-seven patients who were discharged within two weeks after receiving a heart transplant were randomly assigned to participate in a six-month structured cardiac-rehabilitation program (exercise group, 14 patients) or to undergo unstructured therapy at home (control group, 13 patients). Each patient in the exercise group underwent an individualized program of muscular-strength and aerobic training under the guidance of a physical therapist, whereas control patients received no formal exercise training. Cardiopulmonary stress testing was performed at base line (within one month after heart transplantation) and six months later. RESULTS: As compared with the control group, the exercise group had significantly greater increases in peak oxygen consumption (mean increase, 4.4 ml per kilogram of body weight per minute [49 percent] vs. 1.9 ml per kilogram per minute [18 percent]; P=0.01) and workload (mean increase, 35 W [59 percent] vs. 12 W [18 percent]; P=0.01) and a greater reduction in the ventilatory equivalent for carbon dioxide (mean decrease, 13 [20 percent] vs. 6 [11 percent]; P=0.02). The mean dose of prednisone, the number of patients taking antihypertensive medications, the average number of episodes of rejection and of infection during the study period, and weight gain did not differ significantly between the groups. CONCLUSIONS: When initiated early after cardiac transplantation, exercise training increases the capacity for physical work.

Exercise-induced oxidative stress in patients during thallium stress testing.

BACKGROUND: Free radical injury is implicated in the pathogenesis of coronary artery disease, including atherogenesis and reperfusion/injury. Strenuous physical exercise can cause oxidative stress by several mechanisms, including reperfusion/injury. We hypothesize that exercise-induced lipid peroxidation is greater among those with than those without exercise induced myocardial ischemia. METHODS: The effect of physical exercise stress testing on plasma malonaldehyde (MDA) levels was compared between patients with (Group A, N = 8) and without (Group B) exercise-induced myocardial ischemia by thallium imaging. ANALYSIS: Two-way ANOVA was used to compare plasma MDA levels pre- and post-exercise, and paired t-test comparisons were conducted for percent MDA changes between Group A and Group B patients. RESULTS: Two-way ANOVA revealed a significant (P = 0.002) directional difference in response to exercise between the groups' mean plasma MDA levels (Group A increased by 46 +/-12.7 percent, Group B decreased by 16.8+/-4.6 percent). CONCLUSIONS: Differences in exercise-induced lipid peroxidation between patients with and without thallium documentation of myocardial ischemia have important implications in the development of clinical markers of coronary artery disease and further research related to atherogenesis.

Urban angina in the mountains: effects of carbon monoxide and mild hypoxemia on subjects with chronic stable angina.

Seventeen men with stable angina pectoris who resided at or near sea level performed cardiopulmonary exercise stress tests after they were exposed to either carbon monoxide (3.9%), carboxyhemoglobin, or clean air. Investigators conducted the tests at sea level, and they simulated 2.1-km altitudes (i.e., reduced arterial oxygen saturation by approximately 4%) in a randomized double-blind experiment in which each subject acted as his or her own control. The duration of symptom-limited exercise, heart rate, indicators of cardiac ischemia and arrhythmia, blood pressure, and respiratory gas exchange were measured. Analyses of variance showed that both independent variables-altitude and carbon monoxide-significantly (p < or = .01) reduced total duration of exercise for the group as a whole (n=17) and reduced the time to onset of angina for a subset of 13 subjects who experienced angina during all four test conditions (p < .05). Time to onset of angina was reduced either after exposure to sea-level carbon monoxide (9%) or to simulated high-altitude clean-air exposures (11%), compared with clean air at sea level. Joint exposure to carbon monoxide at a simulated high altitude reduced the time to onset of angina, relative to clean air, by 18% (p < .05). Other cardiological, hemodynamic, and respiratory physiological parameters were also affected adversely by altitude and carbon monoxide exposures. None of the parameters measured were associated significantly with either altitude or carbon monoxide, indicating that the effects of carbon-monoxide-induced and high-altitude-induced hypoxia were additive. The results of this study suggest that high-altitude conditions exacerbate the effects of carbon monoxide exposures in unacclimatized individuals who have coronary artery disease.

Changes in VO2max, physical activity, and body fat with chronic exercise: effects on plasma lipids.

The effect of changes in physical activity levels during chronic exercise on plasma lipids and lipoproteins has not been reported. We examine the relationships between changes in VO2max, leisure time physical activity (LTPA), and percent body fat on changes in plasma lipids and lipoproteins in 137 men without coronary artery disease (CAD) and/or dyslipidemia, hypertension, or diabetes mellitus who participated in an employee exercise program. Measurements obtained at entry and 1- and 4-yr follow-up include VO2max, LTPA in kcal.wk-1, percent body fat, and plasma lipids and lipoproteins. The relationship between changes in the measurements between 1 and 4 yr of follow-up (N = 34) revealed the following significant (P < 0.05) correlations: i) changes in VO2max with changes in percent body fat (r = -0.289) and changes in plasma triglycerides (r = -0.354), ii) changes in LTPA with changes in percent body fat (-0.361), and iii) changes in percent body fat with changes in the total/high density lipoprotein (HDL)-cholesterol ratio (0.358), HDL-cholesterol (-0.212), and triglycerides (0.289). Multiple regression analysis revealed that changes in percent body fat affected changes in plasma triglycerides (P < 0.05). The effects of chronic physical activity on plasma triglycerides appear to result from exercise-related effects on body adiposity. These findings support the role of regular physical activity as mandated by Healthy People 2000 for CAD risk reduction.

The effect of exercise intensity on lipid peroxidation.

This study characterizes exercise-induced lipid peroxidation during graded aerobic exercise in seven healthy men and women (36.4 +/- 3 yr). Levels of ethane and pentane in expired breath during cardiopulmonary exercise stress testing were measured at rest, lactic acidosis threshold (LAT), maximal exercise (VO2max), and recovery. Serum malonaldehyde (MDA) levels were measured at rest before exercise and 5 min after maximal exercise. Expired ethane and pentane flux levels were increased above resting levels at LAT, continued to rise at VO2max, then declined during recovery. Serum MDA levels were not significantly different before and after maximal exercise. Substantial exercise-induced lipid peroxidation (by expired ethane and pentane) apparently occurred in healthy individuals at LAT and continued to increase at VO2max, yet rapidly attenuated during post-exercise recovery. These findings indicate that in healthy individuals physical exercise induced lipid peroxidation transiently and that there was a removal of lipid peroxidation byproducts during recovery.

Defining obesity in patients undergoing orthotopic heart transplantation: body mass index versus percent body fat.

We examined body mass index (BMI) as a proxy for percent body fat among 26 men and women successfully undergoing orthotopic heart transplantation. Percent body fat was determined by use of bioelectrical impedance techniques. We found that, although BMI was well correlated with percent body fat (r = 0.58, p < 0.01), use of a BMI of greater than 27 kg/m2 to define obesity potentially misclassified patients when compared with defining obesity as a percentage of body fat as both greater than 30% (BMI = 9 of 26 patients vs percent body fat = 6 of 26 patients) and greater than 40% (BMI = 9 of 26 versus percent body fat = 1 of 9). We conclude that percent body fat measurements are more methodologically appropriate means for J Heart Lung Transplant 1997;16:563-5.

"Lifestyle" interventions for promoting physical activity: a kilocalorie expenditure-based home feasibility study.

The Centers for Disease Control and Prevention and the American College of Sports Medicine in cooperation with the President's Council of Physical Fitness and Sports recommended short periods of daily kilocalorie (calorie) expenditure with moderate-intensity physical activities to complement the currently existing recommendations. In this study the feasibility (adherence and safety) of employing calorie expenditure as the basis for prescribing a home-based walking program to healthy, community-dwelling men and women was examined. This was a 16-week pretest-posttest feasibility study of a home-based calorie-expenditure walking program conducted in an outpatient clinic in an academic medical center. Participants included 20 healthy, elderly, community-dwelling men and women. A 16-week home-based walking program was individually prescribed as a weekly amount of calorie expenditure increasing from an initial 300 calories per week to 1,200 calories per week (approximately 30 minutes of walking daily) during the final 6 weeks of the study. Adherence to the program was recorded individually in a diary (kept daily and reviewed at each visit), body weight, and walking pace. All but one participant were able to complete this 16-week program (95 percent adherence). That a calorie-based approach to promote physical activity among the elderly has a high adherence rate is suggested by these findings. Additional studies are necessary to define the potential role for this approach in promoting physical activity and improving health outcomes among the elderly.

Urban ectopy in the mountains: carbon monoxide exposure at high altitude.

Environmental exposure to inhaled carbon monoxide (CO) increases coronary artery disease risk. Sudden cardiac death, a frequent manifestation of coronary artery disease, is usually a result of ventricular dysrhythmia. The effect of exposure to CO at sea level (CO/SL) and simulated high (2.1 km) altitudes (CO/HA) on the incidence of cardiac ectopy in subjects with coronary artery disease was investigated. A double-blind crossover study was conducted, with random-order assignment, and each subject served as his own control. Seventeen men with documented coronary artery disease and stable angina pectoris performed cardiopulmonary exercise stress tests after random exposure to either CO or clean air (CA) at sea level (CA/SL) or at a simulated 2.1-km high altitude (CA/HA). The individual CO and HA exposure conditions were each selected to reduce the percentage of oxygen saturation of the subjects' arterial blood by 4%. Subjects' blood carboxyhemoglobin levels were increased from an average of 0.62% after clean-air exposure to 3.91% of saturation after CO exposure. The percentage of oxygen saturation in arterial blood was reduced from a baseline level of 98% to approximately 94% after CO/SL or CA/HA and to approximately 90% after CO/HA. Compared with the CA/SL (i.e., 10 premature ventricular contractions [PVCs]), the average incidence of exercise-induced ventricular ectopy was approximately doubled after all exposures (CO/SL = 18 PVCs, CA/HA = 16 PVCs, and CO/HA = 19 PVCs), and a significant trend (p < .05) of increased ectopy with decreased oxygen saturation in arterial blood was observed. Yet, among subjects who were free from ectopy (n = 11) on CA/SL, only 2 subjects developed ectopy after CO/HA. No episodes of ventricular tachycardia or fibrillation occurred. The findings indicated that exposure to increased levels of hypoxemia, resulting from hypoxic and/or CO exposures, increased the susceptibility to ventricular ectopy during exercise in individuals with stable angina pectoris; however, this risk was nominal for those without ectopy.

Acute exposure to carbon monoxide does not affect plasma lipids, lipoproteins, and apolipoproteins.

STUDY OBJECTIVES: To examine the effects of acute exposure to carbon monoxide and hypoxia on plasma lipids, lipoproteins, and apolipoproteins. DESIGN: Random-order assignment to blinded, inhaled exposures of carbon monoxide and hypoxia. SETTING: Research laboratory of ambulatory subjects. SUBJECTS: 10 elderly, male nonsmokers with chronic stable angina. INTERVENTION: Random-order two-hour inhaled exposure to clean air at sea level, carbon monoxide at sea level, carbon monoxide at high altitude, and clean air at high altitude. MEASUREMENTS: Fasting plasma lipids, lipoproteins, and apolipoproteins before and after exposures. RESULTS: No differences were noted between fasting plasma lipid, lipoprotein, or apolipoprotein levels before and after exposures. CONCLUSION: Acute exposure to carbon monoxide and high altitude does not affect fasting plasma lipid, lipoprotein, or apolipoprotein levels.

Incorporation of dietary n-3 fatty acids into the fatty acids of human adipose tissue and plasma lipid classes.

The consumption of n-3 fatty acids from seafood has been related to a lower incidence of coronary artery disease. Adipose tissue composition has served as a biological marker of chronic ingestion of many dietary polyunsaturated fatty acids. However, the incorporation of n-3 fatty acids into the fat depots has not been studied in humans. Daily dietary supplementation with > or = 10 g n-3 fatty acids from fish oil for > 12 mo resulted in significantly greater 20:5n-3, 22:5n-3, and 22:6n-3 concentrations in fatty acids of adipose tissue, and a greater 20: 5n-3 fatty acid content in plasma lipid classes (cholesterol esters, phospholipids, and free fatty acids) of supplemented subjects compared with nonsupplemented control subjects. Combined values for all subjects indicated that fatty acid concentrations of n-3 plasma lipid classes, including 20:5n-3, 22:5n-3, 22:6n-3, and total n-3, significantly correlated with corresponding concentrations of fatty acids in adipose tissue. These findings indicate that the long-term ingestion of large amounts of n-3 fatty acids in humans resulted in their incorporation into the adipose tissue fatty acids. Incorporation of the fatty acids into adipose tissue warrants consideration for use in clinical studies requiring precise documentation of long-term n-3 fatty acid consumption.

A comparison of self-report and chart audit in studying resident physician assessment of cardiac risk factors.

OBJECTIVE: To examine the relationship between resident physicians' perceptions of their preventive cardiology practices and a chart audit assessment of their documented services. DESIGN: A criterion standard comparison of two methods used to assess resident physicians' practices: self-report and chart audit. SETTING: Physician ambulatory care in a residency program. PATIENTS AND OTHER PARTICIPANTS: Coronary artery disease (CAD) risk factor assessment was evaluated by self-report for 72 resident physicians and by chart audit of randomly selected records of 544 of their patients who did not have CAD or a debilitating chronic disease during a one-year period. INTERVENTION: Measurements of the residents' perceived CAD risk factor assessment practice by self-report, and chart audit assessments of their recorded care. MAIN OUTCOME: The relationship between self-reported and chart audit assessments of CAD risk factors. RESULTS: Chart audit assessment of CAD risk factor management was highly significantly (p < 0.01) lower than self-reported behaviors for evaluation of cigarette smoking, diet, physical activity, stress, plasma cholesterol, blood pressure, and body weight/obesity. CONCLUSIONS: Three different interpretations of these findings are apparent. 1) Physician self-report is a poor tool for the measurement of clinical behavior, and therefore research of physician behavior should not rely solely on self-reported data; 2) physicians' chart recording of their clinical practice is insufficient to reflect actual care; or 3) neither is an accurate measure of actual practice.

Lipid disorders: applying new guidelines to your older patients.

The National Cholesterol Education Program Expert Panel has revised its recommendations for managing hypercholesterolemia in adults, including those at midlife and older. In utilizing these guidelines, it is important for the physician to develop an individualized approach to the older patient with hypercholesterolemia. Patient characteristics to consider include lifespan limitations, presence and severity of concomitant disease, mental status and cognitive ability, and the patient's expectations from medical care. Dietary intervention is the first step, with the major focus on restricting saturated fat and cholesterol. Lipid-lowering agents may be warranted in some patients to achieve target LDL levels. Minimize the risk of side effects by careful monitoring and using medications cautiously.

Risk of cardiac dysrhythmias in chronic spinal cord injury patients.

The incidence of cardiac dysrhythmias is characterized in a group of 47 chronic SCI patients (greater than 30 days post injury; range 35-3605 days) with SCI lesions ranging from C4 to L3 who were referred for evaluation of a potential cardiac dysrhythmia by 24 hour Holter monitoring. Patients were grouped according to level of injury as paraplegic (T1 and below), n = 22, or quadriplegic (C3-C8), n = 25. No evidence of life threatening dysrhythmias was noted in either group, and no differences were evidenced in the incidence of cardiac dysrhythmias between the groups. Premature ventricular contractions (PVCs) were noted in 4/25 quadriplegics, and in 1/22 paraplegics, and right bundle branch block (RBBB) was noted in 1/25 quadriplegics and 1/22 paraplegics. A two-year chart review follow up revealed that no clinically significant cardiac dysrhythmic events occurred in these patients. These findings suggest that the risk of cardiac dysrhythmia is attenuated following the acute phases of SCI and represents a diminished concern to the clinician.

Effects of physical exercise training in syndrome X.

Syndrome X categorizes myocardial disease characterized by impaired myocardial flow without macrovessel injury. The pathogenesis of this condition remains obscure. Similarly, therapy is not well defined. We report the effects of physical exercise training in a patient with Syndrome X.

Assessment of adherence to a low-fat diet for breast cancer prevention.

BACKGROUND: The relationships between self-reported adherence to a low-fat diet in healthy women between the ages of 44 and 69 and a number of correlates of this self-reported behavior were examined in an attempt to improve monitoring of adherence to nutritional intervention trials for breast cancer prevention. METHODS: Dietary fat intake in 87 women who completed 6 months of nutritional intervention was reduced from 38.2 +/- 5.9% to 21.7 +/- 7.8% of total energy intake (P less than 0.005). Reported total calorie intake was reduced by approximately 20%. RESULTS: Body weight decreased by 2.7% from 68.1 +/- 11.2 kg to 66.3 +/- 11.9 kg (P less than 0.05). Fasting total plasma cholesterol levels decreased from 205 +/- 31 mg/dl to 184 +/- 29 mg/dl (P less than 0.05). Fasting plasma triglyceride levels did not change significantly (97 +/- 44 mg/dl vs 101 +/- 55 mg/dl). Relative percentage changes in body weight correlated with percentage changes in dietary fat intake (r = 0.23, P less than 0.05). CONCLUSION: Self-reported changes in dietary behavior correlated significantly with objective changes in body weight and fasting cholesterol in these healthy women encouraged to consume a low-fat diet for prevention of breast cancer.

Oral contraceptive use and coronary risk factors in women.

The relationship between oral contraceptive use and other coronary artery disease risk factors was examined in 215 nonsmoking women grouped as never, current, or previous users. Current oral contraceptive users had higher triglyceride levels (p less than or equal to 0.001) than other groups, higher systolic blood pressure, and lower plasma HDL-cholesterol levels (p less than or equal to 0.05) than previous users. The effect of oral contraceptive use on plasma triglyceride values persists on multivariate regression analysis independently of age, body mass index, dietary sodium and cholesterol intake, cigarette smoking, and level of physical activity. Oral contraceptive use also has an independent relationship to the plasma total cholesterol/HDL- cholesterol ratio. These findings indicate that oral contraceptive use is adversely associated with plasma lipid and lipoprotein values.

Reduction of serum estradiol in postmenopausal women given free access to low-fat high-carbohydrate diet.

The short-term effects of a low-fat (less than 10% of cal) high-fiber (35-45 g.1000 kcal-1.day-1) diet on estradiol levels were studied in 13 postmenopausal women under residential conditions with cafeteria food service. During this diet study (mean +/- SE duration 22 +/- 4.6 days), body weight declined from 84.9 +/- 6.4 to 82.3 +/- 6.0 kg (P less than 0.001). Serum cholesterol and low-density and high-density lipoprotein cholesterol also fell significantly, whereas triglycerides remained constant. Serum estradiol fell from 18.1 +/- 3.6 to 9.4 +/- 2.4 pg/ml (P less than 0.05). This study demonstrates that serum estradiol levels are reduced in normal to over-weight postmenopausal women given free access to a low-fat high-fiber diet. Most of these women were in negative caloric balance during the study, suggesting that short-term changes in caloric balance may affect estrogen synthesis in postmenopausal women prior to a large decrease in fat mass.

Overweight: assessment and management issues.

Obesity is associated with an increased risk of coronary artery disease, hypertension, diabetes, hypercholesterolemia, cancer and other conditions. Although generalized obesity is associated with increased risk, the android pattern of body fat distribution may be a more sensitive predictor of coronary artery disease. A gradual weight reduction program, including adherence to a low-fat, calorie-restricted diet and participation in daily exercise, is the best approach to reduce weight and body fat.