Persons with NIDDM, especially women, have abnormal oxygen consumption (V02) responses to exercise even in the absence of clinical cardiovascular disease. We hypothesize that in persons with NIDDM compared to nondiabetic persons, decreased maximal and submaximal cardiac output and/or A-VO2 responses are associated with the observed impaired-V02 responses and that these responses in turn are associated with decreased habitual physical activity level. In addition, we hypothesize that exercise training will improve cardiovascular exercise performance, habitual physical activity level and glycemic control. In addition, we will evaluate whether exercise training is associated with increasing levels of habitual physical activity level in women with NIDDM compared to control values. Subjects will include 10 sedentary premenopausal women with uncomplicated NIDDM, 10 healthy women of similar weight, age and activity level and 10 lean women of similar age and activity level as the women with NIDDM. We will measure the maximal and submaximal responses of VO2, cardiac output and A-VO2 difference (by direct Fick and thermodilution methods) during exercise in premenopausal women with NIDDM. Decreased maximal responses of cardiac output would suggest an cardiac impairment during exercise in NIDDM. Additionally or alternatively, A-VO2 difference responses may be also be abnormal suggesting a peripheral or mixed impairment. To determine whether the decreased VO2max response observed in NIDDM is associate with decreased physical activity level we will compare the three groups using doubly- labeled water techniques. A four month exercise training program will follow the testing procedures which will be repeated upon completion of training. The importance of these studies is 1. to evaluate possible causes of the apparent cardiovascular abnormalities observed in uncomplicated NIDDM. 2. to assess the functional significance of these findings. and 3. to evaluate the modifiability of the responses. This project will enable further understanding of the effects of diabetes on cardiovascular function during exercise as well as the functional significance of exercise impairment in diabetes.