Submitted on May 31, 2005
Accepted on May 18, 2006
AMBULATION IN SIMULATED FRACTIONAL GRAVITY USING LOWER BODY POSITIVE PRESSURE: CARDIOVASCULAR SAFETY AND GAIT ANALYSES
Adnan A Cutuk1, Eli R Groppo1, Edward J Quigley2, Klane W White1, Robert A. Pedowitz1, and Alan R. Hargens1*
1 Department of Orthopaedic Surgery, University of California, San Diego, San Diego, California, United States
2 Motion Analysis Laboratory, Children's Hospital and Health Center, San Diego, California, United States
* To whom correspondence should be addressed. E-mail: ahargens{at}ucsd.edu.
The purpose of this study is to assess cardiovascular responses to lower body positive pressure (LBPP) and to examine the effects of LBPP unloading on gait mechanics during treadmill ambulation. We hypothesized that LBPP allows comfortable unloading of the body with minimal impact on the cardiovascular (CV) system and gait parameters. Fifteen healthy male and female subjects (22-55 yr) volunteered for the study. Nine underwent noninvasive CV studies while standing and ambulating upright in LBPP and six completed a gait analysis protocol. During stance, heart rate (HR) decreased significantly from 83±3 bpm in ambient pressure to 73 ± 3 bpm at 50 mmHg LBPP (p<0.05). While ambulating in LBPP at 3 mph (1.34 m/s), HR decreased significantly from 99±4 bpm in ambient pressure to 84±2 bpm at 50 mmHg LBPP (p<0.009). Blood pressure, brain oxygenation, blood flow velocity through the middle cerebral artery and head skin microvascular blood flow did not change significantly with LBPP. As allowed by LBPP, ambulating at 60% and 20% body weight (BW) decreased ground reaction force (GRF) (p<0.05), while knee and ankle sagittal ranges of motion ROM remained unaffected. In conclusion, ambulating in LBPP has no adverse impact on the systemic and head cardiovascular parameters while producing significant unweighting and minimal alterations in gait kinematics. Therefore, ambulating within LBPP is potentially a new and safe rehabilitation tool for patients that reduces loads on lower body musculoskeletal structures while preserving gait mechanics.
