Mechanical Impedance and Its Relations to Motor Control, Limb Dynamics, and Motion Biomechanics

Abstract

The concept of mechanical impedance represents the interactive relationship between deformation kinematics and the resulting dynamics in human joints or limbs. A major component of impedance, stiffness, is defined as the ratio between the force change to the displacement change and is strongly related to muscle activation. The set of impedance components, including effective mass, inertia, damping, and stiffness, is important in determining the performance of the many tasks assigned to the limbs and in counteracting undesired effects of applied loads and disturbances. Specifically for the upper limb, impedance enables controlling manual tasks and reaching motions. In the lower limb, impedance is responsible for the transmission and attenuation of impact forces in tasks of repulsive loadings. This review presents an updated account of the works on mechanical impedance and its relations with motor control, limb dynamics, and motion biomechanics. Basic questions related to the linearity and nonlinearity of impedance and to the factors that affect mechanical impedance are treated with relevance to upper and lower limb functions, joint performance, trunk stability, and seating under dynamic conditions. Methods for the derivation of mechanical impedance, both those for within the system and material–structural approaches, are reviewed. For system approaches, special attention is given to methods aimed at revealing the correct and sufficient degree of nonlinearity of impedance. This is particularly relevant in the design of spring-based artificial legs and robotic arms. Finally, due to the intricate relation between impedance and muscle activity, methods for the explicit expression of impedance of contractile tissue are reviewed.

Assessment of an Assistive Control Approach Applied in an Active Knee Orthosis Plus Walker for Post-Stroke Gait Rehabilitation

“…The concept of impedance is intricately related to the mode and amount of muscle activation involved in the performance of a given task. Controlling the mechanical admittance of limb joints is an important feature of the neuromuscular system [32], as the output admittance and level of assistance are modified according to the patient disability level [31,33]. In fact, this is of vital interest for researchers involved with the design and control of prosthetic and orthotic devices [34].…”

The Human Motor Cortex Contributes to Gravity Compensation to Maintain Posture and During Reaching

“…Mechanical impedance is defined by the reaction of the musculoskeletal system to perturbations (Mizrahi, 2015); it consists of stiffness and viscosity components. Muscle contractions result in forces that act in either the same or opposite directions around each degree of freedom of the joints they span as determined by muscle anatomy .…”

Effects of Loading on Biomechanical Analysis of Lower Extremity Muscle and Approximate Entropy during Continuous Stair Walking

“…(Edwards, 1984;Gefen, Megido-Ravid, Itzchak, & Arcan, 2002). 이러한 피로는 자신의 동작 수행 능력뿐만 아니 라, 다른 기능들에게까지 영향을 준다 (Mizrahi, 2015;Mizrahi, Voloshin, Russek, Verbitsky, & Isakov, 1997). Yoshino, Motoshige, Araki과 Matsuoka(2004) (Chaloupka, Kang, Mastrangelo, & Donnelly, 1997;Pandy & Andriacchi, 2010;Radin & Rose, 1986;moon, 2004).…”