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Objectives/Hypothesis: Visible light spectroscopy (VLS) is the technology behind the Food and Drug Administration-approved TSTAT device that is used to monitor tissue oxygen (StO2) and relative total hemoglobin (rtHb) levels by measuring reflected visible light. The purpose of this novel, pilot study was to determine if VLS is a reliable and valid method of measuring StO2 and rtHb levels in the human thyroarytenoid/lateral cricoarytenoid (TA-LCA) muscle complex, thus providing information about vocal fold muscle physiology. Study Design: Pre-test/post-test with mulitple baselines and two conditions. Methods: VLS measurements were taken at baseline, during exercise, and following recovery on six subjects using both noncontact channel-port endoscope (endo-probe) and laryngeal electromyography (LEMG) needle-guided techniques. Results: The average baseline StO2 was 69% (standard deviation [SD] = 3.6%) for the LEMG-guided probe and was 71.5% (SD = 2.8%) for the endo-probe. During phonation, the StO2 for the LEMG-guided probe dropped to 59% (SD = 7%; P = .04). Mean rtHb measured by the LEMG probe rose from a baseline of 144 μM (SD = 165 μM) to 214 μM (SD = 166 μM, P = .34) during phonation and back to 149 μM (SD = 139 μM, P = .85) after recovery. Mean rtHb as measured using the endo-probe at baseline and after recovery was 104 μM (SD = 30 μM, P = .76). Conclusions: VLS can be used to measure changes in StO2 and rtHb levels pre- and postexercise in the human TA-LCA muscle complex. Laryngoscope, 121:2429-2434, 2011 [ABSTRACT FROM AUTHOR]