The purpose of this study was to develop new methodologies to measure muscle metabolism and blood flow in older humans, both with normal and reduced blood flow (peripheral vascular disease). Progress in this year was testing of a method using partial cuff ischemia during recovery from submaximal exercise. With MRS, we measure PCr recovery with a blood pressure cuff (positioned on the upper leg) inflated to 0, 50, 60, 70, and 90 mmHg. Similar measurements are made using duplex Doppler to determine the relative effect of the partial cuff pressures on muscle blood flow. NIRS measurements of oxygen saturation were collected during both MRS and Doppler measurements. Preliminary results suggest normal subjects have no impairment in PCr recovery with flow reductions up to 25%. With greater flow reductions, both flow and PCr recovery are impaired. Significant correlations were found between NIRS recovery and peak Doppler flow after ischemia in patients with mild PVD. Acceptab le levels of reproducibility suggest additional data will allow mathematical determination of relative contributions of blood flow and mitochondrial capacity in determining muscle metabolism in elderly healthy and diseased subjects.
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