JOINT STIFFNESS - MYTH OR REALITY

The notion of joint stiffness as commonly studied in biomechanics and motor control is compared with the physical definition of stiffness. T he importance of elastic deformation and storage of elastic energy is stressed. Different terms are suggested in order to differentiate betw een experimentally observed relations between joint angle and torque t hat are likely to have different nature. A review of studies measuring stiffness of joint subcomponents and intact joints is presented. We s uggest to either abandon the term 'joint stiffness' as misleading or t o state up front stiffness of which of the joint components or subsyst ems is analyzed in each particular study. We also suggest that each st udy of 'joint stiffness' should clearly state to what extent the resul ts are defined by the system's properties and to what extent they are reflections of the particular experimental procedure.