Introduction: One way to quantify vascular dysfunction of an individual is to examine Flow Mediated Dilation (FMD). Aerobic exercise is characterized by increased blood flow and has been shown to either prevent or mitigate vascular dysfunction. However, exercise may not always be possible, especially in occupational settings that require long bouts of sitting or standing. Localized heating of the lower limb may be an alternative, especially since it also increases blood flow. However it is unknown how localized heating affects vascular function during prolonged sitting and standing. Purpose:The purpose of this study was to look at the effect that localized heating of the lower leg had on the FMD of the superficial femoral artery. We hypothesized that compared to the unheated leg; FMD will increase in the heated leg, indicating improved vascular function. Methodology: 26 healthy adults (13 male and 13 female) 18-30 years old completed this study. Participants completed 2 experimental trials. In one trial, subjects stood for 120 minutes while in the other trial the participants were required to sit for the 120 minutes. In both trials the treated leg was randomly selected, and a water perfusion suit was applied to the lower portion on the subjects leg (knee to ankle) and heated by circulating 49 °C water through the suit. Before, during (measurements where taken at the 10, 25, 50, 85, and 120 minutes) and after the experimental trial heart rate (HR) and mean arterial pressure (MAP) were recorded. FMD was measured before and after the 120 minutes of sitting/standing while the participant was in the supine position. Results:While controlling for FMD in the heated leg compared to the unheated leg did not significantly increase (1.49% 95% CI [-.01, 3.1]). In other words, there was a non-significant main effect of heating on FMD. Both MAP and HR increased during the standing and sitting periods, but returned to the baseline once the participant was supine. MAP increased by 9 mmHg (SD= 8.1, p\u3c.001) and HR increased by 20 beats per minute (SD= 13.4; p\u3c.001). Conclusion:The results of this study shows that localized heating of one lower limb during long duration sitting and standing did not increase FMD. However, in the control, unheated leg FMD did not decrease, thus it may not be too surprising that heat stress had no effect. That is, FMD could have been at a “ceiling” with no more room for improvement. However, larger, future studies should investigate if the statistically non-significant increase is clinically significant. Likewise, future studies should investigate if the setup could be applied to an occupational setting
