title: Optimal calibration of instrumented treadmills using an instrumented pole.
abstract: Calibration of instrumented treadmills is imperative for accurate measurement of ground reaction forces and center of pressure (COP). A protocol using an instrumented pole has been shown to considerably increase force and COP accuracy. This study examined how this protocol can be further optimized to maximize accuracy, by varying the measurement time and number of spots, using nonlinear approaches to calculate the calibration matrix and by correcting for potential inhomogeneity in the distribution of COP errors across the treadmill's surface. The accuracy increased with addition of spots and correction for the inhomogeneous distribution across the belt surface, decreased with reduction of measurement time, and did not improve by including nonlinear terms. Most of these methods improved the overall accuracy only to a limited extent, suggesting that the maximal accuracy is approached given the treadmill's inherent mechanical limitations. However, both correction for position dependence of the accuracy as well as its optimization within the walking area are found to be valuable additions to the standard calibration process.
authors.affiliation: VU University Medical Center, Department of Rehabilitation Medicine, PO Box 7057, 1007 MB Amsterdam, The Netherlands; Research Institute MOVE, VU University Amsterdam, Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands. Electronic address: l.sloot@vumc.nl.
authors.forename: L H
authors.initials: LH
authors.lastname: Sloot
authors.affiliation: Research Institute MOVE, VU University Amsterdam, Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands; Heliomare Rehabilitation Center, Research and Development, Relweg 51, 1949 EC Wijk aan Zee, The Netherlands. Electronic address: h.houdijk@vu.nl.
authors.forename: H
authors.initials: H
authors.lastname: Houdijk
authors.affiliation: VU University Medical Center, Department of Rehabilitation Medicine, PO Box 7057, 1007 MB Amsterdam, The Netherlands; Research Institute MOVE, VU University Amsterdam, Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands. Electronic address: m.vanderkrogt@vumc.nl.
authors.forename: M M
authors.initials: MM
authors.lastname: van der Krogt
authors.affiliation: VU University Medical Center, Department of Rehabilitation Medicine, PO Box 7057, 1007 MB Amsterdam, The Netherlands; Research Institute MOVE, VU University Amsterdam, Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands. Electronic address: j.harlaar@vumc.nl.
authors.forename: J
authors.initials: J
authors.lastname: Harlaar
mesh_terms: D002138:Calibration; D005080:Exercise Test / Q000295:instrumentation*; D017711:Nonlinear Dynamics; D013997:Time Factors
keywords: Biomechanics; Center of pressure; Gait analysis; Kinematics; Kinetics