A new system for the measurement of displacements of the human body with widespread applications in human movement studies

This paper reports the development, construction and use of a new system fo r the measurement of linear kinematics in one, two or three dimensions. The system uses a series of rotary shaft encoders and inelastic tensioned stri ngs to measure the linear displace ment of key anatomical points in space. The system is simple, inexpensive, portable, accurate and flexible. It is t herefore suitable for inclusion in a variety of motion analysis studies. De tails of the construction, calibration and interfacing of the device to an IBM PC computer are given as is a full mathematical description of the appr opriate measurement theory for one, two and three dimensions. Examples of t he results obtained from the device during gait, running, rising to stand, sitting down and pointing with the upper limb are given. Finally it is prop osed that, provided the constraints of the system are considered, this meth od has the potential to measure a variety of functional human movements sim ply and inexpensively and may therefore be a valuable addition to the metho ds available to the motion scientist. (C) 1999 IPEM. Published by Elsevier Science Ltd, All rights reserved.