Ambulatory measurement of ground reaction forces

P.H. Veltink, C. Liedtke, E. Droog and H. van der Kooij

Institute for Biomedical Technology (BMTI), University of Twente, Enschede, The Netherlands

The measurement of ground reaction forces is important in the biomechanical analysis of gait and other motor activities. Many applications require full ambulatory measurement of these forces, but this is not supported by current measurement systems. We propose the use of two six degrees of freedom force and moment sensors under each shoe, which enables the ambulatory measurement of ground reaction forces and Centers of Pressure (CoP). The feasibility of this method is illustrated by experimental results in a healthy subject, using a force plate as a reference. The ground reaction forces and CoP recordings show good correspondence when they are evaluated for forces above 40 N and when it is simply assumed that the sensors are .at on the ground when they are loaded. The RMS difference of the magnitude of the ground reaction force over 12 gait trials was 15 ± 2 N, corresponding to 1.9 ± 0.3 % of the maximum ground reaction force magnitude. The RMS difference of the horizontal component of the ground reaction force was 3 ± 2 N, corresponding to 0.4 ± 0.2 % of the maximum ground reaction force magnitude and to 2 ± 1 % of the maximum of the horizontal component of the ground reaction force. The RMS distance between both CoP recordings is 2.9 ± 0.4 mm, corresponding to 1.1 ± 0.2 % of the length of the shoe, when the trajectories are optimally aligned.

Paper presented at Measuring Behavior 2005 , 5^th International Conference on Methods and Techniques in Behavioral Research, 30 August - 2 September 2005, Wageningen, The Netherlands.

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