Skeletal muscle and cardiovascular adaptations to exercise conditioning in older coronary patients.

BACKGROUND: Older coronary patients suffer from a low functional capacity and high rates of disability. Supervised exercise programs improve aerobic capacity in middle-aged coronary patients by improving both cardiac output and peripheral extraction of oxygen. Physiological adaptations to aerobic conditioning, however, have not been well studied in older coronary patients. METHODS AND RESULTS: The effect of a 3-month and a 1-year program of intense aerobic exercise was studied in 60 older coronary patients (mean age, 68 +/- 5 years) beginning 8 +/- 5 weeks after myocardial infarction or coronary bypass surgery. Outcome measures included peak aerobic capacity, cardiac output, arterio-venous oxygen difference, hyperemic calf blood flow, and skeletal muscle fiber morphometry, oxidative enzyme activity, and capillarity. Training results were compared with a sedentary, age- and diagnosis-matched control group (n = 10). Peak aerobic capacity increased in the intervention group at 3 months and at 1 year by 16% and 20%, respectively (both P < .01). Peak exercise cardiac output, hyperemic calf blood flow, and vascular conductance were unaffected by the conditioning protocol. At 3 and 12 months, arteriovenous oxygen difference at peak exercise was increased in the exercise group but not in control subjects. Histochemical analysis of skeletal muscle documented a 34% increase in capillary density and a 23% increase in succinate dehydrogenase activity after 3 months of conditioning (both P < .02). At 12 months, individual fiber area increased by 29% compared with baseline (P < .01). CONCLUSIONS: Older coronary patients successfully improve peak aerobic capacity after 3 and 12 months of supervised aerobic conditioning compared with control subjects. The mechanism of the increase in peak aerobic capacity is associated almost exclusively with peripheral skeletal muscle adaptations, with no discernible improvements in cardiac output or calf blood flow.

A controlled trial of exercise training in older coronary patients.

BACKGROUND: This study compared the effects of a formal exercise conditioning program of 3 and 12 months duration to spontaneous recovery in a population of older, post-coronary event patients. METHODS: Indices of peak exercise and submaximal exercise performance such as oxygen consumption, treadmill work capacity, minute ventilation, heart rate, and systolic blood pressure were assessed before and after conditioning in 60 post-myocardial infarction and post-coronary bypass surgery patients (mean age 68 +/- 5 years) and compared to measures of fitness in a usual care control group (n = 23, mean age 68 +/- 5 years). RESULTS: Maximal treadmill work capacity increased by 47% in the intervention group at 3 months compared to no improvement in the usual care control group. However, both groups increased peak oxygen consumption similarly at 3 and 12 months, increasing by 16% and 20% in the intervention group at 3 and 12 months and by 7% and 14% in the control group (p = n.s.). Only the exercise training group manifested submaximal indices of conditioning such as a lower heart rate and minute ventilation at a standard workload. CONCLUSION: While spontaneous improvements in peak oxygen consumption are seen in older coronary patients in the months following a coronary event, a formal exercise training program results in significantly greater increases in peak exercise capacity and in peak and submaximal exercise efficiency.

Exercise conditioning in older coronary patients. Submaximal lactate response and endurance capacity.

BACKGROUND: Older coronary patients are at high risk of cardiac disability. Exercise conditioning programs have been demonstrated to improve functional capacity, particularly in younger coronary patients. In this study, the effects of aerobic conditioning on submaximal and maximal indicators of exercise performance were examined in 45 older coronary patients. METHODS AND RESULTS: Forty-five patients (mean age, 69 +/- 6 years; range, 62 to 82 years) entered 3-month and 12-month (n = 11) endurance training programs. Training effects were assessed during an exhaustive submaximal exercise protocol with measurement of endurance time, serum lactate, perceived exertion, and expired ventilatory measures. Exhaustive endurance time increased by more than 40% (30 +/- 10 to 41 +/- 10 minutes), with associated decreases in serum lactate, perceived exertion, minute ventilation, heart rate, and systolic blood pressure during steady-state exercise. Respiratory exchange ratio during steady-state exercise, an indicator of substrate utilization, decreased, indicating a shift toward greater use of free fatty acids as a metabolic fuel. In a subset of 10 patients, percent body fat was decreased (32 +/- 8% to 29 +/- 10%) over a period of 3 months. CONCLUSIONS: Older coronary patients respond to aerobic conditioning with remarkable improvements in submaximal endurance capacity, out of proportion to the more modest increases in VO2max. Activities that were exhaustive before training became sustainable for extended periods of time at a lower perceived exertion. Measurements of serum lactate, respiratory exchange ratio, and ventilation during steady-state exercise document that at an identical absolute work load after conditioning, exercise is performed using aerobic substrate to a greater degree, and ventilatory response to a given work load is lessened.

Referral patterns and exercise response in the rehabilitation of female coronary patients aged greater than or equal to 62 years.

Gender-related differences in cardiac rehabilitation referral patterns and response to an aerobic conditioning program were examined in 226 hospitalized older coronary patients (aged greater than or equal to 62 years). Overall, the outpatient cardiac rehabilitation participation rate in this population was 21%. Older women were less likely to enter cardiac rehabilitation than were older men (15 vs 25%; p = 0.06), despite similar clinical profiles. This was explained primarily by a greater likelihood of primary physicians to strongly recommend cardiac rehabilitation to men. Before conditioning, women who entered cardiac rehabilitation were less fit than were men; peak oxygen consumption was 18% lower in women (16 +/- 5 vs 20 +/- 5 ml/kg/min; p = 0.02). However, both groups improved aerobic capacity similarly in response to a 12-week aerobic conditioning program, with maximal oxygen consumption increasing by 17% in women and by 19% in men. Thus, older female coronary patients are less likely to be referred for cardiac rehabilitation, despite a similar clinical profile and improvement in functional capacity from the training component.

Predictors of cardiac rehabilitation participation in older coronary patients.

BACKGROUND: While older coronary patients have a lower exercise capacity than younger coronary patients and have been demonstrated to improve exercise capacity to a degree similar to younger coronary patients, they are less likely to be referred to an outpatient cardiac rehabilitation program. The goal of this study was to determine demographic, medical, and psychosocial predictors of outpatient cardiac rehabilitation participation in hospitalized older post--coronary event patients. METHODS: An in-hospital-guided interview was performed by the clinical research nurse of the cardiac rehabilitation program with 226 hospitalized patients, aged 62 years and older, who had recently suffered a myocardial infarction or coronary bypass surgery. Demographic, medical, and psychosocial data were analyzed. RESULTS: Overall cardiac rehabilitation participation rate in a population with a mean age of 70.4 +/- 6 years (range, 62 to 92 years) was 21%. By multivariate analysis, the strength of the primary physician's recommendation for participation was the most powerful predictor of cardiac rehabilitation entry. Also, significant predictors of participation included commute time, patient "denial" of severity of illness, and history of depression. Medical factors such as cardiac diagnosis and left ventricular ejection fraction did not predict participation. CONCLUSIONS: Demographic, medical, and psychosocial data, collected in hospitalized post-coronary event patients are powerful predictors of subsequent participation in cardiac rehabilitation.