Ambulation in simulated fractional gravity using lower body positive pressure: cardiovascular safety and gait analyses

Abstract

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 system and gait parameters. Fifteen healthy male and female subjects (22-55 yr) volunteered for the study. Nine underwent noninvasive cardiovascular studies while standing and ambulating upright in LBPP, and six completed a gait analysis protocol. During stance, heart rate decreased significantly from 83 +/- 3 beats/min in ambient pressure to 73 +/- 3 beats/min at 50 mmHg LBPP (P < 0.05). During ambulation in LBPP at 3 mph (1.34 m/s), heart rate decreased significantly from 99 +/- 4 beats/min in ambient pressure to 84 +/- 2 beats/min 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 decreased ground reaction force (P < 0.05), whereas knee and ankle sagittal ranges of motion 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 to reduce loads on lower body musculoskeletal structures while preserving gait mechanics.

Return to sport following hip injury

“…The net ground reaction force then becomes the difference between the weight of the user and this axial force. Increasing axial force (un-weighting) will decrease GRF [8]. The user can be un-weighted from 99% of body weight down to 20% of body weight in 1% increments.…”

“…Ground reaction forces are reduced for running and walking at all levels of un-weighting using the LBPP treadmill versus full body weight [8,12,[14][15][16]. Running mechanics are not significantly affected with un-weighting with respect to stride length and knee and ankle sagittal plane ROM [8,17,18].…”

Effect of Lower Body Positive Pressure on Fluid Turnover in Human Legs

“…Many patients after orthopedic surgery or stroke have difficulty in walking due to muscle weakness, partial paralysis and/or leg pain 1,2) . Various devices for gait training including canes, walkers, parallel bars and suspension harnesses are used for unloading the lower extremities during walking rehabilitation 1,2) .…”

“…Various devices for gait training including canes, walkers, parallel bars and suspension harnesses are used for unloading the lower extremities during walking rehabilitation 1,2) . Their main objective is to start rehabilitation as early as possible.…”

“…Their main objective is to start rehabilitation as early as possible. Hargens and his colleagues 2) reported that applying lower body positive pressure (LBPP) could reduce ground reaction force (GRF), or apparent body weight, in upright human. The device not only reduces GRF, but also possibly affects body fluid turnover in the legs because applying LBPP around the legs may decrease capillary filtration rate and/or increase lymph drainage from the tissues.…”