The effects of increasing body weight support on gait kinematics and tibial shock during treadmill running
Lower body positive pressure (LBPP) treadmills have become a popular modality for both training and return to sport rehabilitation. The literature outlining the efficacy of LBPP treadmills for training and rehabilitation in elite athletic groups is limited. The purpose of this research was to examine the effects body weight support (BWS) treadmill running has on the kinematic variables of running gait; and on tibial shock during submaximal treadmill running in a cohort of elite athletes. Twenty elite (male =9, female = 11), international level athletes who represented New Zealand in a variety of team and individual Olympic sports volunteered to participate in this study. A repeated-measures design, using quantitative measures, was performed to determine changes in tibial accelerometery and sagittal plane gait kinematics while running on the Alter-G Trainer treadmill. Tibial acceleration was used to determine tibial shock and two-dimensional video analysis was performed to determine sagittal plane gait kinematics. All variables were assessed at 60, 70, 80 and 90% of body weight, and were measured against the control condition of 100% body weight. Tibial shock reduced as BWS increased, however not linearly. Very large and large effect sizes (ES) were observed for 60% condition (ES = 0.71), and 70% conditions (ES = 0.59) respectively. A moderate change for 80% condition (ES = 0.35) was observed while only a trivial change in mean was observed for the 90% condition (ES =0.09). Trivial to small changes were observed for changes in ankle angles across all conditions, with the exception of Initial Contact and Mid-stance angles at 60% conditions. Large and very large changes were observed for tROM at 60% (ES = 0.51) and 70% (ES = 0.79). Stride rate and foot strike patterns were also affected at the 60% condition. The change at 60% for foot strike was extremely large (ES = 1.29). The incidence of fore-foot strike (FFS) increased by 30% at 60% condition but not at lower levels of BWS. Running with BWS on a LBPP treadmill is effective for unloading the magnitude of tibial shock in the lower limb. LBPP treadmills may be an effective piece of equipment for rehabilitation purposes with appropriate consideration of kinetic and kinematic variables and how these interact, relative to the lower limb injury.