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.