Changes in mechanical work during treadmill-induced asymmetric walking

Asymmetric walking patterns are common in healthy and clinical populations. While minor asymmetries are likely benign, greater asymmetries may negatively affect physical function and mobility. Changes in mechanical work may largely explain why walking asymmetry influences physical function and mobility. Thus, the purpose of this study was to describe how increasing the degree of walking asymmetry affects limb- and joint-level mechanical work. Ten healthy participants walked on a force-instrumented split-belt treadmill for a total of 33 min. Participants began by walking for 6 min at 1.2 m/s with both treadmill belts moving at equal speeds (0 % condition). After the 0 % condition, the speed of the right belt was reduced by 10, 25, and 50 % while the left belt maintained a constant speed of 1.2 m/s. To visualize the distribution of work within each limb, pie charts were developed by calculating the relative work performed by each joint/segment to the total absolute limb work. To determine the effect of walking asymmetry on mechanical cost of transport (CoT), we constructed a 2x4 (limb-by-condition) repeated measures ANOVA model. There was a significant limb-by-condition interaction (p < 0.0001), with CoT decreasing in the fast limb and increasing in the slow limb as asymmetry increased. However, the joint-level distribution of work remained relatively unchanged across walking conditions. Therefore, inducing asymmetric walking in healthy adults appears to alter mechanical costs while only minimally affecting joint/segment-level compensations. Future research should focus on individuals with pathologies to determine if similar strategies are observed.