Effect of walking speed on the intersegmental coordination of lower-limb segments in elderly adults

Background: Ageing brings profound changes in walking gait. For example, older adults reduce the modification of pelvic and trunk kinematics with walking speed. However, the modification of the coordination between lower-limb segments with age has never been investigated across various controlled speeds. Research question: Is the effect of speed on the intersegmental coordination different between elderly and young adults? Methods: Nineteen senior and eight young adults walked on a treadmill at speeds ranging from 0.56 to 1.94 m s(-1). The motion of the lower-limb segments in the sagittal plane was recorded by cinematography. When the angles of the thigh, shank and foot during a stride are plotted one versus the other, they describe loops constraint on a plane. The coordination between lower-limb segments was thus evaluated by performing a principal component analysis between the thigh, shank and foot elevation angles. The effect of speed and age on the intersegmental coordination was examined using a two-level linear mixed model ANOVA. Results: In both age groups the orientation of the plane changes with speed, due to a more in-phase shank and foot motion. However, the effect of speed on the covariation plane is lessened with age. Significance: Our results demonstrate that there is an age-related specific adjustment of the intersegmental coordination to speed. In particular, older adults restrict their repertoire of angular segment motion. These differences in coordination are mainly related to different foot-shank coordination.