On the relationship between resultant joint torques and muscular activity

Abstract

This paper is an investigation of the relationship between resultant joint torques and in vivo muscular activity. This relationship is currently inaccessible by direct experimental measurements due to the limited usefulness of electromyographic (EMG) data to indicate muscle force reliably and to proscriptions and experimental difficulties related to in vivo measurements on human subjects. The standard indirect method for inferring information about this relationship, using model studies in conjunction with temporal EMG data, is discussed. Key assumptions incorporated in these model studies, which lead to values for the joint force and torque resultants, are reviewed. The general distribution problem is formulated, and key assumptions associated with generating the simplified distribution problem that governs muscle activity are described. Two basically different methods for solving the simplified distribution problem and therefore determining the approximate relationship between resultant joint torques and muscular activity, including methods that attempt to account for the effect of antagonistic muscular activity, are discussed.