Compensation of stochastic time-continuous perturbations during walking in healthy young adults: An analysis of the structure of gait variability

Abstract

BackgroundDuring everyday locomotion, we cope with various internal or external perturbations (e.g. uneven surface). Uncertainty exists on how unpredictable external perturbations increase noise within the motor system and if they are compensated by employing covariation of the limb joints or rather due to decreased sensitivity of an altered posture. Research questionDo continuous stochastic perturbations affect the structure of gait variability in young and healthy adults? MethodsIn a cross-over study, gait kinematics of 21 healthy young sports students were registered during treadmill walking with and without continuous stochastic perturbations. Using the TNC method, the following aspects were analyzed: (a) the sensitivity of body posture to perturbations (‘tolerance’) decreasing gait variability, (b) the unstructured motor ‘noise’ increasing gait variability and (c) the amount of ‘covariation’ of the limb joints. ResultsCompared to normal walking, gait variability was significantly increased (p < .001) during walking with perturbations. The negative effect of noise was partly compensated by improved ‘covariation’ of leg joints (p < .001). The aspect ‘tolerance’ had a small effect on increasing gait variability during stance phase (p < .001) and decreasing gait variability during swing phase (p < .001). SignificanceIncreased motor noise due to external perturbations is partly compensated by improved covariation of the limb joints. However, the effect of an altered posture slightly affects gait variability. Further studies should focus on different populations (e.g. older participants) to see if they use the same mechanism (improved covariation) to compensate for stochastic perturbations.