Blood pressure responses to different arm positions during vertical head-down ankle suspension.

This study compares the effects of different arm positions on blood pressure during vertical head-down ankle suspension. Eighteen healthy volunteers (10 men and 8 women, aged 20-30 years) were placed first in the upright sitting position for 4 min, and second in the head-down suspension position for 4 min. In the latter position, the arms were first alongside the head and then raised alongside the body at the end of the 4th min. Blood pressure was measured non-invasively during the last 30 s of the 4th min of upright sitting and head-down suspension with the arms alongside the head, and then immediately following the movement of the arms alongside the body. In relation to the upright sitting position, head-down suspension with the arms dangling alongside the head resulted in a significant increase in brachial artery blood pressure (121/78 mm Hg vs. 146/91 mm Hg, respectively). This finding may be explained on the basis of a variable hydrostatic component. Following the immediate movement of the arms to alongside the body while still suspended, there was a significant decrease in blood pressure to 124/79 mm Hg. No significant change in blood pressure occurred from upright sitting to full head-down suspension with the arms alongside the body (121/78 mm Hg vs. 124/79 mm Hg, respectively). Based on previous disparate reports of pressure during head-down suspension, the findings of the present study indicate a need to standardize the method of blood pressure measurement during this procedure.