Biomedical subjects

J R Schairer

Publications and source records attributed to J R Schairer.

7 recordsLinked to original sources

PubMed1999

Effects of exercise training on chronotropic incompetence in patients with heart failure.

OBJECTIVE: To describe the effects of exercise training on chronotropic incompetence in patients with stable heart failure, as measured by their inability to achieve a peak exercise heart rate greater than 85% of maximum. BACKGROUND: Exercise intolerance and chronotropic incompetence are characteristic of patients with heart failure. Exercise training improves exercise capacity in these patients; however, to what extent reversal of chronotropic incompetence contributes to such a response remains uncertain. METHODS: Fifty-one patients undergoing standard medical therapy were randomly assigned to a 24-week exercise training program or a no exercise control group. Twenty-one of 26 patients assigned to the exercise group and 22 of 25 control patients completed the study. Peak oxygen consumption, resting and exercise plasma norepinephrine level, and quality of life (Living With Heart Failure Questionnaire) were assessed. RESULTS: A significant (P <.05) increase in peak heart rate was observed in the exercise group (9 +/- 3 beats/min) when compared with the control group (1 +/- 3 beats/min). Among exercise-trained patients with chronotropic incompetence at baseline (n = 14), the increase in peak heart rate at week 24 was 12 +/- 3 beats/min. Peak oxygen consumption was significantly (P <.05) increased in the exercise group (204 +/- 57 mL/min) versus the control group (72 +/- 33 mL/min). Health-related quality of life was not significantly changed with exercise training. Twenty-four weeks of exercise training induced a greater (P <.05) reduction in plasma norepinephrine at rest and during exercise in patients with a nonischemic cardiomyopathy versus those with ischemic cardiomyopathy. CONCLUSIONS: Exercise training results in an increase in peak heart rate and partial reversal of chronotropic incompetence among patients with stable heart failure. These responses contribute, in part, to the exercise training-induced increase in exercise capacity that occurs in these patients.

Cardiac Output↗

PubMed1996

Exercise training in patients with heart failure. A randomized, controlled trial.

OBJECTIVE: To assess the benefit of exercise training in patients with heart failure caused by left ventricular systolic dysfunction and to further describe the physiologic changes associated with exercise training in these patients. DESIGN: Randomized, controlled trial. SETTING: Urban outpatient clinic. PATIENTS: 40 men with compensated heart failure who were receiving standard medical therapy were randomly assigned to an exercise-training group or to a control group that did not exercise. Fifteen of the 21 patients assigned to exercise training and 14 of the 19 patients assigned to the control group completed the study. INTERVENTION: Patients assigned to exercise training participated in a program of three exercise sessions per week for 24 weeks. MEASUREMENTS: Symptom-limited exercise tests with gas exchange analysis done just before randomization, at week 12, and at week 24. RESULTS: At week 24, the following changes (mean +/- SE) were seen in patients in the exercise group and patients in the control group, respectively; exercise duration, 2.8 +/- 0.6 minutes and 0.5 +/- 0.5 minutes; peak oxygen consumption (VO2), 231 +/- 54 L/min and 58 +/- 38 L/min; peak ventilation, 12 +/- 3 L/min and -4 +/- 3 L/min; peak heart rate, 10 +/- 4 beats/min and -2 +/- 4 beats/min; and peak power output, 20 +/- 6 W and 2 +/- 5 W. Differences between the increases occurring in the exercise group and the changes occurring in the control group were significant (P < 0.05). Among patients in the exercise group, 85% of the increase in peak VO2 occurred by week 12, and 46% of the increase in peak VO2 was caused by the increase in peak heart rate. CONCLUSION: Exercise training does not appear to be contraindicated in patients with compensated heart failure. Exercise training improved exercise tolerance, as measured by increases in peak VO2, exercise duration, and power output. This improved exercise tolerance was caused in part by an increase in peak heart rate.

Adult↗

PubMed1993

Left ventricular wall tension and stress during exercise in athletes and sedentary men.

This investigation examines the hypothesis that hypertrophy attenuates wall stress during exercise, when left ventricular wall tension is highest and most likely to contribute to hypertrophy. Upright bicycle exercise was performed by 17 endurance-trained male athletes and 15 sedentary men. M-mode echocardiograms were obtained during submaximal exercise at predetermined heart rates. At all levels of exercise, at a matched heart rate, wall tension was higher in athletes than in sedentary subjects. In both groups, wall tension increased with exercise, then plateaued. Wall stress did not differ significantly in athletes and sedentary subjects at rest and at heart rates of 110 and 150 beats/min, although a difference was observed at a heart rate of 130 beats/min. Wall stress decreased in both athletes and sedentary subjects with exercise. In conclusion, left ventricular hypertrophy caused wall stress in athletes to be maintained at values similar to sedentary subjects during exercise as well as at rest.

Adult↗

PubMed1992

Left ventricular response to submaximal exercise in endurance-trained athletes and sedentary adults.

This investigation examines the hypothesis that athletes increase stroke volume with submaximal exercise through an augmentation of left ventricular (LV) end-diastolic volume and a reduction of LV end-systolic volume, whereas sedentary adults only increase stroke volume modestly, because LV end-diastolic volume does not increase. Upright bicycle exercise was performed by 17 endurance-trained male athletes and 15 sedentary men. M-mode echocardiograms were obtained during submaximal exercise at predetermined heart rates. Athletes, at a heart rate of 130 beats/min, increased their stroke volume 67% from 72 +/- 18 ml to 120 +/- 26 ml (p less than 0.001). This resulted from an increase of LV end-diastolic volume from 119 +/- 23 to 152 +/- 28 ml (p less than 0.001) and a reduction in LV end-systolic volume from 46 +/- 14 to 31 +/- 9 ml (p less than 0.001). Sedentary men at the same heart rate increased stroke volume 22% from 63 +/- 15 to 77 +/- 21 ml (p less than 0.05). LV end-diastolic volume did not change (96 +/- 20 vs 97 +/- 28 ml) (p = not significant), but LV end-systolic volume decreased (33 +/- 11 vs 20 +/- 9 ml) (p less than 0.001). In conclusion, athletes increased cardiac output through a more prominent augmentation of stroke volume than sedentary subjects at submaximal exercise. This was accomplished through an augmentation of LV end-diastolic volume. This may have a conserving effect on myocardial oxygen consumption at these levels of exercise.

Adult↗

PubMed1991

Left ventricular function immediately after exercise in elite cyclists.

To determine the response to exercise of the left ventricle of endurance-trained athletes, 6 elite (world class) cyclists were compared to 6 untrained healthy control subjects. In athletes the stroke volume increased with exercise. In untrained volunteers the stroke volume did not change with exercise. This difference of the response of the stroke volume to exercise reflected a difference of the left ventricular end-diastolic volume. In athletes the left ventricular end-diastolic volume tended to increase. In control subjects the end-diastolic volume decreased. In conclusion, athletes increased cardiac output by increasing stroke volume and heart rate, whereas control subjects increased their cardiac output only by increasing their heart rate.

Adolescent↗

PubMedDate not supplied

Exercise testing and training of patients with heart failure due to left ventricular systolic dysfunction.

Reducing the exercise intolerance and symptoms experienced by patients with chronic heart failure remains an important focus in their clinical care. A clear shortcoming exists; however, with respect to an appreciation that in addition to standard medical therapy, selected patients with stable heart failure also can benefit from a moderate exercise training program. Improvements in central transport, regional blood flow, and skeletal muscle histology and biochemistry all likely account for the increase in exercise capacity and delay in fatigue that these patients experience. Additionally, the autonomic imbalance that is characteristic of these patients is improved. Although the number of patients with heart failure participating in an exercise program is increasing, much work still exists relative to incorporating this treatment method into the care plans established by physicians and physician extenders.

Exercise Test↗

PubMedDate not supplied

Caloric expenditure during cardiac rehabilitation.

PURPOSE: The purpose of this study was to describe estimated caloric expenditure among patients in a maintenance cardiac rehabilitation program relative to a stated goal of approximately 300 kcal/session or 1,000 kcal/week. Additionally, we assessed the validity of several different methods for estimating caloric expenditure. METHODS: The caloric expenditure for an exercise session was evaluated in 30 of 65 patients exercising in a maintenance cardiac rehabilitation program. Patients exercised using a treadmill, dual-action ergometer, upright stepper, or reclining stepper. The kilocalorie expenditure was assessed by three different techniques. The first used liquid crystal display (LCD) readings from the equipment (LCD method), the second combined both the American College of Sports Medicine metabolic equations for treadmill walking and the LCD values from the other equipment (Combined method), and the third measured oxygen consumption (VO2 method). RESULTS: The caloric expenditure for the LCD, Combined, and VO2 methods were 247 +/- 83, 245 +/- 80, and 230 +/- 88 kcal, respectively. Agreement between methods using intraclass correlation analysis was r = 0.84 (0.68 to 0.92, 95% confidence intervals) for LCD versus VO2 and r = 0.88 (0.77 to 0.94, 95% confidence intervals) for Combined versus VO2 method. CONCLUSIONS: Most patients (83%) in a maintenance cardiac rehabilitation program exercise below 300 kcal per session, a level believed to be necessary to illicit favorable changes in cardiovascular health. Additionally, the Combined method provides a reasonable estimate of kilocalorie expenditure. Use of kilocalorie expenditure should be considered in the cardiac rehabilitation setting as a fourth component in the exercise prescription.

Energy Metabolism↗