Alter-G® Treadmill Chamber Pressure at Three Unweighted Conditions in College Age Volunteers

Lower body positive pressure (LBPP) treadmills utilize an inflatable chamber to provide a range of unweighted conditions for specific rehabilitation or training purposes. This is achieved by pumping air into the chamber, which results in a lower body lift or unweighted condition. Creating an unweighted condition for the user lessens the impact on the lower body during treadmill exercise. Yet, little is known about internal chamber air pressure changes during unweighted conditions and its effect on arterial blood pressure (BP). The purpose of this investigation was to study changes in chamber air pressure (CAP), arterial BP, and heart rate (HR) across three unweighted conditions. Participants (38 college age students, ages 18-21) stood in the LBPP treadmill chamber under positive pressures of 35%, 70%, and 90% unweighted conditions. CAP was measured using a portable Davis Vantage weather station barometer, arterial BP was measured with a SunTech® automatic BP cuff, and HR was measured using an apple watch. Measurements were recorded at the end of each 3-minute stage for each condition. Preliminary results of a pilot study show changes in average CAP during the three unweighted conditions of 767.2, 752.8, and 744.4 mm Hg, respectively. Interestingly, arterial BP remained constant despite greater chamber pressure. Average resting arterial BP for each condition was 122.5/76.5, 126/73, and 116/72.5 mm Hg at 35%, 70%, and 90% unweighted conditions, respectively. The following findings are the first to demonstrate internal chamber air pressure across different unweighted conditions.