M.Sc Thesis

M.Sc StudentSuponitsky Yulianna
SubjectEffect of Fatigue of the Shank Muscles on Single-Leg-
Standing Balance
DepartmentDepartment of Biomedical Engineering
Supervisor PROFESSOR EMERITUS Joseph Mizrahi
Full Thesis textFull thesis text - English Version


Posture control during upright standing involves continuous muscular activity, associated with body sway. In single-leg standing, the base of support is narrower compared to double standing and the body becomes more unstable. The result is an increased body sway, emphasizing the role of individual muscles in regulating the sway motion. Muscle fatigue takes place as a result of an intensive activity of the muscles and can serve as a good model of particular muscle function failure.

The goal of this study was to examine the effects of conjugated fatigue of two frontal shank muscles (Tibialis Anterior and Peroneus) on posture control in single-leg standing.

The methodology consisted of conducting a series of experiments theoretical analysis. Each experiment consisted of two single-leg standing trials separated by a 240 s quasi-isotonic sustained effort to induce fatigue of Tibialis Anterior and Peroneus muscles.

The fatigue effect in single-leg standing was evaluated by means of the correlations between postural sway parameters including the COP and GRF and activities of three shank muscles, including the Tibialis Anterior, Peroneus and Gastrocnemius. Additionally, the double inverted pendulum model was used to estimate the effect of muscle fatigue on the ankle and hip torques and stiffness. The model includes three main parts: (a) the biomechanical model, describing skeletal dynamics during one-leg standing and based on anthropometrical data; (b) estimation of the joint angles and (c) closed-loop control system.

The main finding of this study is that the correlation between muscle activity and posture sway significantly increases as a result of muscle fatigue. It was found that muscle fatigue impairs the posture control, but some important posture control parameters don’t change as a result of muscle fatigue.