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Session: Neuro-muscular – lower extremities 2
Session starts: Friday 25 January, 13:00
Presentation starts: 14:00
Room: Lecture room 536

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Eline Flux (Amsterdam UMC, Vrije Universiteit Amsterdam, Department of Rehabilitation Medicine, Amsterdam Movement Sciences, de Boelelaan 1117, Amsterdam, the Netherlands)
Ronald van 't Veld (Department of Biomechanical Engineering, University of Twente)
Marjolein van der Krogt (Amsterdam UMC, Vrije Universiteit Amsterdam, Department of Rehabilitation Medicine, Amsterdam Movement Sciences, de Boelelaan 1117, Amsterdam, the Netherlands)

Abstract:
Introduction Many people with neurological impairments experience increased resistance in joints, which is caused by velocity dependent stretch hyperreflexia (increased reflex activity), increased background muscle activity and/or altered tissue properties [1]. Measures of quantifying components of joint resistance are important for clinical decision making and could be used for training focused on decreasing hyperreflexia (e.g. [2]-[3]). Ludvig et al. [4] developed an online system identification (SI) method which can be used to separate components of joint resistance and to quantify reflex activity. An adapted version of this method [5] has been validated by comparing SI outcomes to EMG outcomes for various activation levels. Our study aims to supplement the validation of this SI method to determine the possibilities of implementing this method in clinical decision making and training. Methods Twelve healthy adults (7 male, 21.3±2.0y) participated in this study. Participants were seated in a chair, the Dyno 2.0, with their right foot connected to a single axis actuator by means of a footplate. Perturbations were applied around the ankle joint (±0.0175 rad, maximum 2.74 rad/s). Participants were exposed to a control condition and two experimental conditions known to facilitate reflexes: experienced pain induced by a cold pressor task and the Jendrassik maneuver (JM [6]). Reflex activity was measured [5] and averaged over a 90 second periods. EMG reflex activity was measured using the ensemble average of 150 perturbations of the gastrocnemius EMG signal as described previously [5]. Results Reflexes were significantly higher during experienced pain and JM compared to control, both according to SI and EMG measures. Furthermore, good correlations were found (r=0.75-0.89) between SI and EMG measures during all conditions, further supporting the validity. Conclusions The online SI method as developed by Ludvig et al. [4] and modified by van ‘t Veld et al. [5] appears a valid measure to use in training. Further research should study the distinctive probabilities of the method between reflex activity and tissue properties, for example by including conditions which influence tissue properties. Furthermore, a generalizability study should be performed (e.g. [7]) to assess reliability, before implementation in clinical decision making. [1] Van den Noort, Eur J Neurol 24-7 (2017) 981-38. [2] Thompson, Front Integr Neurosci 8 (2014) 25. [3] Ludvig, Exp Brain Res 183-2 (2007) 201–213. [4] Ludvig, IEEE Trans Biomed Eng 54-10 (2007) 1875–1884. [5] Van 't Veld, BioRob proceedings. [6] Dowman, Exp Neurol 101-2 (1988) 288-302. [7] Roebroeck, Phys Ther 73-6 (1993) 386-395.