AGE, SEX & BALANCE BTW CARDIAC OUTPUT & MUSCLE BLOOD FLOW IN EXERCISING HUMANS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Older sedentary men preserve blood flow to the working muscles by directing a higher percentage of their cardiac output to the working limbs and having an exaggerated pressor response relative to young men. In contrast, aged women cannot maintain leg blood flow during upright cycling exercise and attempt to optimize leg blood flow by an even further exaggerated pressor response during upright exercise. This protocol will address this issue to determine the effect of aging on the interplay between exercising muscle demand for perfusion and the pumping capacity of the heart in aged humans. Additionally, the subject groups studied will consist of sufficient sample sizes to assess ageXsex interactions in each of the variables measured, a methodological perspective rarely taken in human physiology. Hypothesis: The peak perfusion measured during maximal single leg extension exercise in aged women and men, when extrapolated to the entire limb muscle mass, will exceed the cardiac pumping capacity by a greater degree in the older women and men than younger sex-matched subjects indicating a greater need to vasoconstrict working skeletal muscle in aged women and men.