Symmetry and reproducibility of the components of dynamic stability in young adults at different walking velocities on the treadmill

In the literature, analysis of dynamic gait stability using the extrapolated center of mass concept is often an objective that assumes reproducible and symmetrical data. Here, we examined the validity of this assumption by analyzing subjects walking at different velocities. Eleven healthy young subjects walked on a treadmill at six different velocities (1.0–2.0 m · s−1). Dynamic stability at touchdown of the left and right foot (10 gait trials for each body side) was investigated by using the margin of stability, determined as the difference between base of support and extrapolated center of mass. Dynamic stability parameters showed no significant differences (P > 0.05) between gait trials, with a root mean square difference in margin of stability of less than 1.62 cm. Correlation coefficients between trials were above 0.70 for all parameters, demonstrating that two gait trials are sufficient to obtain reproducible data. In more than 90% of the cases, the absolute symmetry index was below 8% with no relevant functional differences between body sides. We concluded that analyzing two gait trials for one body side is sufficient to determine representative characteristics of the components of dynamic stability in healthy young adults while walking on the treadmill at a wide range of velocities.