Vertical ground force distribution in healthy subjects performing lower body positive pressure treadmill exercise
MetadataShow full item record
OBJECTIVE: Accidents continue to remain one of the leading causes of death in the elderly, with falls being at the top of the list. Death does not always result from the fall itself, but rather the complications that arise from extended bed rest and reambulation after the incident. A focus needs to be placed on determining how to improve rehabilitative protocols, decreasing overall time of bed rest before returning to their normal quality of living. Lower Body Positive Pressure (LBPP) is a rehabilitative method that incorporates the benefits of unweighting patients in order to expediate their recovery process. LBPP’s effect on gait mechanics remains to be explored. This study aims to understand the effects of different levels of speed and LBPP on foot strike pattern. We hypothesized that with increased LBPP there would be a shift to a forefoot strike (FFS) from baseline foot strike behavior. We then hypothesized that this FFS would return back to a typical rearfoot strike (RFS) pattern with increased speed of exercise. METHODS: Ten healthy subjects participated in a walking and running exercise trial with LBPP. The subjects walked at a pace of 2 miles per hour (mph), and jog at 6mph for five different levels of LBPP, 100%, 80%, 60%, 40%, and 20% of their total bodyweight. Data analysis was performed by examining force and pressure underneath the feet during each stance phase of the exercise performed. RFS and FFS were measured using a force by stance graph for both speeds, as well as 3-D framed pictures of the pressure underneath the feet at precise moments of each subject’s stance phase. RESULTS: The data showed a presence of a RFS before transfer of force to the forefoot at 2mph. The data also showed that a RFS was present before transfer of force to the forefoot at 6mph. Subjects weighing less than 55 kilograms (kg) exhibited more of a FFS at 2mph than subjects weighing greater than 55kg. There were several strike pattern differences in the data of subjects weighing greater than and less than 55kg. There was significance (P<0.05) found in the comparison of force and stance’s, as well as the comparison of speed and stance’s effect on the degree of variation within the data. Multiple comparisons performed between each level of unweighting found significance (P<0.0001) between each different level at different speeds. CONCLUSION: The lack of a FFS with increased LBPP at 2mph did not support our first hypothesis. Our results did support the second hypothesis that increased speed displays more of a RFS pattern with increased LBPP. Strength may have been the cause of difference in strike pattern between subjects weighing less and more than 55kg, because subjects weighing >55kg could force a RFS at high levels of LBPP, while subjects weighing <55kg could not. Several subjects also noted that they forced their normal RFS at the highest levels of LBPP while walking at 2mph, because of the abnormality of their movement.