Asymmetric leg activity in healthy subjects during walking, detected by electrogoniometry

Aim. To show asymmetric leg activity during walking in healthy subjects. Design. Two electrogoniometers were used to measure the amplitude of the flexion-extension movements of both knees during walking. Background. Walking is considered to be a symmetrical activity. Quantitative studies of walking often only consider one side of the body or remove differences between individuals by averaging results. Methods. The handedness, lateral eye dominance and footedness of 31 healthy subjects were determined. A strain gauge electrogoniometer was then fitted to the outside of each knee to analyze the flexion-extension movements. The results were recorded automatically. The subject walked a distance of 30 m three times, with different attention levels: free walking (with no other task assigned), walking with attention diverted (whilst performing a mental task), and focused walking (walking as straight as possible in a straight line). Results. 51.6% of the subjects tested displayed asymmetry of the total flexion-extension movement of more than 5° between the two knees during free walking. The side favored (preponderance) by this asymmetry was not related to the handedness or other lateral dominance. The different attention levels did not significantly affect the characteristics of motion of the sub-groups studied (symmetric, right-favoring and left-favoring). Conclusions. The origin of this asymmetry, which is independent of handedness or attention level, could be the spinal stepping generator for which there is evidence in both animals and humans. Walking should not be considered to be a strictly symmetrical phenomenon.