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The Influence Of Gender On Functional Sympatholysis: 1142 Board #7 June 1, 3: 15 PM - 5: 15 PM.

PURPOSE:The purpose of this investigation was to better understand gender differences related to sympathetically induced global vasoconstriction and functional sympatholysis. METHODS:Ten male and 10 female volunteers with no significant differences in physical activity, age, and height were recruited for this investigation. For the duration of the protocol, participants were resting in the supine position. Participants initially performed 3 stages of incrementally increasing handgrip exercise at 15, 30 and 45% MVC with 1 minute of recovery following each stage. Following a 20 minute recovery, this protocol was repeated with continuous application of -30 mmHg LBNP distal to the iliac crest. Heart rate (HR), heart rate variability (HRV), stroke volume (SV), mean arterial pressure (MAP), brachial artery blood flow (BBF), brachial artery diameter (DIAM) and forearm muscle oxygenation changes were measured continuously. RESULTS: When examining the effects of HR, there was a pressure x intensity x gender interaction (p=0.04), a main effect of pressure (p=0.002) and a main effect of intensity (p<0.001). Regarding SV, there was a main effect of pressure (p=0.004) and a main effect of gender (p=0.04). There was a main effect of intensity (p<0.001) on MAP in that MAP increased for males and females across all intensities. Regarding the BBF response, there was a main effect of gender (p=0.001), intensity (p<0.001) and a gender x intensity interaction (p<0.001). Females had overall reduced BBF compared to males, which increased less as exercise intensity increased compared to the males. HRV indicated no significant increases in sympathetic activity in both males and females. CONCLUSIONS:In the present study -30 mmHg negative pressure was not a strong enough stimulus to elicit significant peripheral vasoconstriction in our group of young, healthy participants. Therefore we cannot speculate as to whether gender differences exist in sympathetic vasoconstriction or functional sympatholysis.