Abstract 9: Calf Muscle Oxygenation During Exercise in Healthy Adults

Abstract

Objective: To develop an exercise test to detect mismatches between calf muscle tissue metabolism and oxygenation. Design: Cross-sectional, quasi-experimental, repeated measures. Setting: Large urban tertiary care medical center. Participants: 43 healthy adults, aged 20 to 40 years, any ethnicity or gender. Intervention: While in semirecumbent posture on a hospital bed, subjects underwent a testing protocol consisting of 7 test stages of 5 minutes each: rest, 0-W active plantarflexion/dorsiflexion, rest, 4-W plantarflexion, rest, 8-W plantarflexion, and rest. The Stresst’er pedal ergometer was used for resistive calf muscle exercise. Tissue oxyhemoglobin saturation (Sto2, %) was digitally acquired at the medial calf site in 3- to 4-second intervals by near-infrared spectroscopy (Hutchinson InSpectra Tissue Spectrometer model 325). This technique measures Sto2 in skin, subcutaneous tissue, and muscle to a depth of 25mm. Main Outcome Measures: Maximum Sto2 during 0-W exercise and minimum Sto2 during 4- and 8-W exercise. Results: Wilcoxon signed-rank tests showed that, compared with previous resting baseline, maximum Sto2 during 0-W exercise increased significantly (P=.000; 6%). Also, minimum Sto2 during 4- and 8-W exercise decreased significantly (P=.000; 9% and 13%, respectively). No exercise intolerance was noted for any subject during the protocol. Conclusions: The mildest exercise (0-W active plantarflexion and dorsiflexion) improved muscle oxygenation over resting baseline. This test was also able to detect significant tissue desaturation during nonfatiguing, mild-to-moderate intensity, resistive plantarflexion exercise in healthy adults. The degree and duration of the desaturation may provide an objective test for the assessment of physiologic and functional impairment and functional outcome in patients with peripheral vascular disease and claudication.