Development of a low-cost video vector for the display of ground reaction forces during gait

Video vector systems offer a simple and valuable tool suitable for evaluating and analysing the biomechanics of human motion. These systems are capable of widespread applications in education, clinical evaluation and research. However, the literature indicated that current video vector systems are expensive and not widely available. The work presented in this study indicates an alternative method of constructing a video vector system which is inexpensive and relatively simple to build. The system uses a VGA to video adaptor to convert computer-generated graphics of the ground reaction force into a video formet. This picture can then be overlaid on to a video picture of the moving subject using a video mixer. By careful positioning of the camera and suitable perspective drawing of the computer image a true representation of the relationship between the force vector and the subject can be produced. The system has been found to be reliable, versatile and robust and has been used for a variety of motion analysis tasks. It is hoped that the work contained in this paper will encourage others to construct their own video vector systems using similar commercially available components and hence benefit from the considerable advantages that such a system can offer. This paper describes the design and construction of a simple, inexpensive video vector system which has been shown to be a useful biomechanical technique with widespread applications in the educational, clinical and research environments.