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Miranda K. Traylor, Amanda M. Cuomo, Sylvie M. Gray, Ethan C. Hill, Joshua L. Keller. University of South Alabama, Mobile, AL.

Background: During vascular occlusion tests (VOT) and with near-infrared spectroscopy (NIRS), it has been shown that men desaturate and re-saturate faster than women, yet inconsistencies have been reported. Therefore, our purpose was to determine if sex differences in VOT variables would persist after normalizing for adipose tissue thickness (ATT), bilateral leg extension one-repetition maximum (1RM), leg circumference, and lean body mass (LBM). Methods: Thirty-one adults (16 men, 15 women) were assessed during a VOT as well as for 1RM, ATT and LBM. A NIRS device was attached to the vastus lateralis during the VOT (1 min baseline, 5 min of femoral artery occlusion, 3 min reperfusion). Before this VOT, an ultrasound quantified ATT. Leg circumference was determined by a tape measure. Body composition was determined via FIT3D. The 1RM was defined as the maximum load moved through the complete range of motion of a bilateral leg extension. The VOT was 9 min and a data point for the skeletal muscle tissue oxygenation (StO2,%) was determined every 30-s yielding 18 data points. Following the calculation of these points, they were normalized to the previously defined participant characteristics. Separate 2-way ANOVAs (Sex x Time) were used to examine mean differences in the following: uncorrected StO2, StO2-ATT, StO2-1RM, StO2-leg circumference, StO2-LBM. A p<0.05 was considered significant. Results: The men exhibited greater 1RM (98.2±11.9 vs. 59.4±11.6 kg), leg circumference (57.2±4.8 vs. 51.8±3.4cm), and LBM (64.5±9.7 vs. 45.6±4.9 kg), but the women exhibited greater ATT value (0.77±0.2 vs. 0.54±0.2 cm). The uncorrected NIRS-VOT responses indicated that there was an interaction (p<0.001), and the follow-up t-tests demonstrated that men desaturated and re-saturated faster than women. When normalizing the downslope values to circumference and ATT, the men still exhibited a faster rate of desaturation than women, but normalizing to LBM or strength eliminated this difference. The upslope findings matched the downslope responses. Conclusion: Sex differences related to microvascular responses were partially robust to our normalization approaches. Specifically, we again reported that men exhibit faster rates of desaturation and re-perfusion even when accounting for leg size and ATT, which further supports the notion that these differences are perhaps due to mitochondrial function and/or muscle fiber type.

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