Open Access
Chavanaves, Sakdapong
Graduate Program:
Doctor of Philosophy
Document Type:
Date of Defense:
March 03, 2017
Committee Members:
  • Robert B. Eckhardt, Dissertation Advisor
  • Robert B. Eckhardt, Committee Chair
  • Jinger S. Gottschall, Committee Member
  • Robert L. Sainburg , Committee Member
  • Gregory S. Lewis, Outside Member
  • Stephen J. Piazza, Dissertation Advisor
  • Stephen J. Piazza, Committee Chair
  • gait
  • variability
  • stability
  • local divergence exponent
  • reliability
  • walking speed
  • symmetry
  • lateralization
There are over 7 million fall injuries in the United States across all ages annually. Previous studies have shown that falls occurred most frequently during walking. To identify individuals at high risk of falling, we need objective measures which are reliable, valid and easily applicable to quantify fall risk. Gait variability and local dynamic instability have been shown to be able to distinguish healthy gait and fall-prone gait. This dissertation explores gait variability and local dynamic stability of foot and trunk in human walking using accelerometers. Three studies were conducted to examine: (1) how the intra-session and inter-session reliability of gait variability and local dynamic stability was affected by the number of strides analyzed, walking conditions and calculation methods, (2) the effect of walking speed on gait variability and local dynamic stability and (3) how gait variability and local dynamic stability differs between left and right foot under different walking conditions. In all three studies, the gait variability investigated were stride time variability and the variability of foot and trunk accelerations. The local dynamic instability was quantified using short-term and long-term local divergence exponents. In Study 1 and 3, four different walking conditions at preferred walking speed were examined, namely treadmill, overground on a rectangular path, clockwise and counterclockwise on a circular path. In Study 2, five different walking speeds at 60%, 80%, 100%, 120% and 140% of preferred walking speed on a treadmill were investigated. In Study 1, the results suggest that the optimal reliability of the variability of acceleration and short-term local divergence exponents may be achieved with at least 75 strides. The intra-session reliability may be improved by research design that minimizes the variability in experimental settings and equipments. Overall, the reliability was better when gait variability and local divergence exponents were calculated using foot accelerations compared to trunk accelerations. Gait variability and long-term local divergence exponents were more consistent in counter-clockwise than clockwise walking, suggesting that these variables may be linked to turning preference and limb dominance. In Study 2, the results revealed that stride time variability decreased with walking speed. The variability of acceleration and long-term local divergence exponents increased with walking speed. The effect of walking speed on short-term local divergence exponents varied depending on calculation methods. Collectively, these results suggest that future studies should control walking speed when these variables are compared between different groups or conditions. In Study 3, the variability of acceleration was larger for the left foot compared to the right foot in all walking conditions except in the medial-lateral direction, implying that motor lateralization may influence the control of lower limbs motion. The short-term local divergence exponents were not different between left foot and right foot in all walking conditions except in the medial-lateral direction, suggesting that motor lateralization may not affect the control of gait stability and that gait variability and local dynamic instability are different quantities which reflect different aspect of gait characteristics.