Jiayi Ning

Advisors
Markus Gambietz (M.Sc.), Prof. Dr. Anne Koelewijn

Duration
11 / 2021 – 05 / 2022

Abstract
This thesis will investigate the relationship between step frequency and gait kinetics and kinematics. Step frequency is an important gait variable, since it is known that people choose their step frequency such that metabolic energy expenditure is minimized [1]. However, when gait kinetics and kinematics are analysed, often averages are taken over different experimental participants without accounting for differences in step frequency [2], where the inherent assumption is that gait kinetics and kinematics are independent on step frequency. This has been investigated with 10 participants for the ground reaction force, but not for other kinetic and kinematic parameters [3].

However, recently, a predictive gait simulation study found that there might be some dependence between gait kinetics and kinematics and step frequency [4]. Predictive simulations were found by solving a trajectory optimization. It was found that, when minimizing an objective that was a combination of effort (square muscle actuation) and tracking of joint angles and ground reaction forces, the step frequency where the effort objective was minimized was different from the step frequency where the tracking objective was minimized. This would imply that there is so me relationship between these tracked variables and the step frequency which is currently not understood.

Therefore, the goal of this thesis is to investigate the relationship between step frequency and gait kinetics and kinematics. A gait analysis experiment will be performed, where participants are asked to walk on an instrumented treadmill at different step frequencies and a fixed speed. Marker data and ground reaction forces will be recorded, which will be processed and investigated to evaluate differences in the joint angles, ground reaction forces, and joint moments between step frequencies.

References:
[1] Zarrugh, M. Y., et al.: Optimization of energy expenditure during level walking. European journal of applied physiology and occupational physiology, 33(4), 293-306, 1974.
[2] Winter, D. A.: Kinematic and kinetic patterns in human gait: variability and compensating effects. Human movement science, 3(1-2), 51-76, 1984.
[3] Martin, P. E., and Marsh, A.P.: Step length and frequency effects on ground reaction forces during walking. Journal of biomechanics 25(10), 1237-1239, 1992.
[4] Koelewijn, A. D., and Selinger, J. C.: Predictive Simulations of Gait with Exoskeletons that Alter Energetics. in prep, 2021.