Effects of dynamic exercise training on the metabolic and cardiocirculatory responses to exercise in the rat model of myocardial infarction and heart failure.

In an effort to produce significant systemic circulatory training effects, including adaptations of the heart, myocardial infarcted (MI) rats were subjected to 2 training regimens: low-intensity endurance training (LIET) and high-intensity endurance training (HIET). When compared with sedentary controls, the MI rats subjected to LIET had small but significant beneficial systemic circulatory training effects exclusive of any training effects on the heart. MI rats subjected to HIET had similar but more extensive and quantitatively greater circulatory adaptations than those found in MI rats subjected to LIET. Unlike LIET MI rats, the HIET MI rats had an increase in maximal heart rate when compared with sedentary MI rats. However, despite the reversal of this chronotropic incompetence, the HIET MI rats did not have significant increases in parameters indicative of increased left ventricular pump function (maximal cardiac output) and maximal stroke volume. To further study the effect of incrementally increasing exercise intensity, a high-intensity sprint training (HIST) regimen was developed and studied in normal rats. In response to HIST, normal rats had central myocardial adaptations (increases in maximal cardiac output and stroke volume) in response to training that were not found in the MI rats subjected to LIET and HIET. Although the effects of HIST in normal rats is now known, the question of whether a training paradigm consisting of HIET and HIST will produce increases in maximal cardiac output and stroke volume in the MI rat has yet to be determined.