Effects of Increased Step Width on Knee Biomechanics in Healthy-weight and Obese Populations During Inclined and Declined Walking

The purpose of this study was to investigate effects of preferred step width and increased step width modification on knee biomechanics, specifically peak knee abduction and extension moments, of obese and healthy-weight participants during incline and decline walking. Seven healthy weight participants and six obese participants categorized by BMI values performed five walking trials on level ground and a 10° inclined and declined instrumented ramp system. Two AMTI force platform(s) were used to collect GRF data (1200 Hz, AMTI,). 3D kinematic data were collected a motion capture system (240 Hz, Vicon). All data were imported into 3D data analysis software, Visual3D (version 2.6, C-Motion, Inc., Germantown, MD, USA) for 3D kinematic and kinetic analysis. A 2 x 2 (step-width x group) mixed model ANOVA was used to examine selected variables. There were significant increases in step width (SW) between the preferred and wide SW conditions for all three walking conditions (all p<0.001). An interaction was found for peak KEM (p=0.048) and KAbM (p=0.025) in uphill walking. During downhill walking, there were no interaction effects. As SW increased, KAbM was reduced (p=0.007). In level walking there were no interaction effects for peak mediolateral GRF and KAbM (p=0.007). There was a SW main effect for KAbM (p=0.007). As SW increased, peak mediolateral GRF and peak KEM increased, while KAbM decreased for both groups. It was found that increasing SW may be a useful strategy for reducing KAbMs in healthy, young populations.