Cardiac Function as the Limiting Factor of Exercise

概要

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Several factors influence exercise performance. Peak oxygen uptake (peakVO_2), an index of the maximal aerobic exercise capacity, represents oxygen supplied by the cardiovascular system and oxygen demand on exercising skeletal muscles. Therefore, exercise-limiting factors are divisible by central factors such as cardiac output (CO), heart rate (HR), and peripheral factors such as peripheral circulation and metabolic characteristics of skeletal muscles. Although cardiac function is presumed to be the central factor, left ventricular (LV) systolic function index is not significantly related to peakVO_2. Using echocardiography and peakVO_2 in elderly subjects, we have investigated the relation between LV function and exercise. The resting index of LV relaxation and response of increased HR were adopted as limiting factors of exercise in elderly subjects. LV systolic function index was not significantly related to peakVO_2. For that reason, two-dimensional echocardiography can not adequately evaluate cardiac contraction-relaxation coupling. To elucidate cardiac function more clearly as a limiting factor of exercise, three-dimensional echocardiography must be used to evaluate LV twisting and untwisting.