A comprehensive protocol to test instrumented treadmills.
Instrumented treadmills are becoming more common in gait analysis. Due to their large and compliant structure, errors in force measurements are expected to be higher compared with conventional force plates. There is, however, no consistency in the literature on testing the performance of these treadmills. Therefore, we propose a standard protocol to assess and report error sources in instrumented treadmills. The first part of this protocol consists of assessment of the accuracy of forces and center of pressure (COP), including non-linearity, hysteresis and crosstalk. The second part consists of (novel) instrumented resonance testing and belt speed variability tests. The third part focuses on measurement variability over time, including drift, warming of the system and noise. The performance of two in-house instrumented treadmills with different dynamics was measured. Differences were found between the treadmills in COP accuracy (4.0 mm versus 6.5 mm), lowest eigen frequency (35 Hz versus 23 Hz) and noise level at 5 km/h (10 N versus 29 N). The loaded treadmills both showed a 3.3% belt speed variability at 5 km/h. Thus, the protocol was able to characterize strong and weak characteristics of the treadmills and allowed for a proper judgement on the validity of the instruments and their application in the domain of gait analysis. We propose to use this protocol when testing and reporting the performance of instrumented treadmills.
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.
L H
LH
Sloot
Research Institute MOVE, VU University Amsterdam, Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands; Heliomare Rehabilitation, Research and Development, Relweg 51, 1949 EC Wijk aan Zee, The Netherlands.
H
H
Houdijk
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.
J
J
Harlaar
D001696:Biomechanical Phenomena; D002138:Calibration; D005080:Exercise Test / Q000295:instrumentation*; D005684:Gait; D006801:Humans; D017711:Nonlinear Dynamics; D026741:Physical Therapy Modalities / Q000295:instrumentation*; D011312:Pressure
Biomechanics; Calibration; Gait analysis; Rehabilitation medicine; Treadmill testing