Design and Construction of a Novel Low-Cost Device to Provide Feedback on Manually Applied Forces

Abstract

Design and evaluation, technical note. To describe the design of a simple, low-cost device for providing feedback of manually applied forces to the cervical spine, and to assess the device against specific design criteria. The forces applied during manual therapy may vary by as much as 500% between practitioners. But consistency can be improved in students when they are provided with contemporaneous feedback. The current methods of providing feedback, however, are expensive, complex, and/or preclude their performance in a clinically relevant manner. The design of the device was assessed in accordance of the following criteria: (1) ease of use, (2) low cost, (3) minimal interference with technique, (4) ability to provide feedback with suitable accuracy at forces up to 50 N, and (5) no requirement of specialized skills to construct. A device is described that interfaces with standard computers through the sound card and measures force, using thin, low-cost, force-sensing resistors. Evaluated against the design criteria, the device (1) is easy to set-up and use, (2) can be produced for under $30 US dollars, (3) creates minimal interference with performance of a variety of techniques, (4) has limits of agreement from -3.8 to 4.2 N for forces of 5 to 45 N and repeatability coefficients of ± 2.0 N or 12%, and (5) can be constructed without specialized skills or knowledge. A device is described that fulfills most of the design criteria for providing feedback on forces for physical therapy students and may have applications in other fields.