Modeling muscle activity to study the effects of footwear on the impact forces and vibrations of the human body during running

• Published in: Journal of biomechanics 2010-01, Vol.43 (2), p.186-193
• Main Authors: Zadpoor, Amir Abbas, Nikooyan, Ali Asadi
• Format: Article
• Language: English
• Subjects: Algorithms; Biological and medical sciences; Biomechanical Phenomena; Central Nervous System - physiology; Compliance; Experiments; Footwear; Fundamental and applied biological sciences. Psychology; Ground reaction force; Human body; Humans; Hypotheses; Leg - physiology; Modeling; Models, Biological; Muscle tuning; Muscle, Skeletal - innervation; Muscle, Skeletal - physiology; Nonlinear Dynamics; Personal relationships; Physical Medicine and Rehabilitation; Running; Running - physiology; Shoes; Simulation; Studies; Vertebrates: body movement. Posture. Locomotion. Flight. Swimming. Physical exercise. Rest. Sports; Vibration; Vibrations
• ISSN: 0021-9290; 1873-2380
• DOI: 10.1016/j.jbiomech.2009.09.028

Abstract A previously developed mass-spring-damper model of the human body is improved in this paper, taking muscle activity into account. In the improved model, a nonlinear controller mimics the functionality of the Central Nervous System (CNS) in tuning the mechanical properties of the soft-tissue package. Two physiological hypotheses are used to determine the control strategies that are used by the controller. The first hypothesis (constant-force hypothesis) postulates that the CNS uses muscle tuning to keep the ground reaction force (GRF) constant regardless of shoe hardness, wherever possible. It is shown that the constant-force hypothesis can explain the existing contradiction about the effects of shoe hardness on the GRF during running. This contradiction is emerged from the different trends observed in the experiments on actual runners, and experiments in which the leg was fixed and exposed to impact. While the GRF is found to be dependent on shoe hardness in the former set of experiments, no such dependency was observed in the latter. According to the second hypothesis, the CNS keeps the level of the vibrations of the human body constant using muscle tuning. The results of the study show that this second control strategy improves the model such that it can correctly simulate the effects of shoe hardness on the vibrations of the human body during running.