[Efficacy of home exercise program in a convalescent phase of acute myocardial infarction evaluated by Borg's indices, expiratory gas analysis and blood lactate].

The Borg's indices, the rate of perceived exertion have been widely accepted to evaluate subjective symptoms semi-quantitatively in exercise tests. We applied the indices to evaluate the efficacy of our home exercise program in patients with acute myocardial infarction. Eighty-five patients were entered in our home exercise program after their discharge from the hospital. This program consisted of everyday 2 km walk-jog exercise for 1 month keeping their heart rate at 100-110/min during the exercise. Before and 1 month after their discharge, they underwent treadmill exercise tests with expiratory gas analysis and a measurement of blood lactate. In the treadmill tests performed before and after the training, VO2 and heart rate increased linearly with Borg's indices, however VE and blood lactate had disproportionate increases after Borg's 13 which is considered to be the anaerobic threshold (AT). In fact, AT measured individually by expiratory gas analysis and blood lactate, appeared at Borg's 13 in 53% of the patients. After 1 month physical training, VO2 and heart rate significantly increased at the same Borg's indices, but there was no significant changes in blood lactate at the same Borg's score before and after the training. These results suggest that, in patients with acute myocardial infarction, exercise performance significantly increased at any score of subjective symptoms and that Borg's indices may reflect the blood lactate levels. It is concluded that Borg's indices, closely related to the dynamics of blood lactate, are not only useful in quantifying subjective symptoms but also to estimate the efficacy of physical training.