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Session: Poster session I
Session starts: Thursday 24 January, 15:00

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Bouke Scheltinga ()
Mohamed Irfan Mohamed Refai ()
Carel Meskers ()
Erwin van Wegen ()
Gert Kwakkel ()
Bert-Jan van Beijnum ()

Abstract:
A measure for quality of movement during reaching tasks is ‘movement smoothness’. It is related to the continuity of a movement, independent of amplitude and duration of the movement [1]. In stroke patients, it is shown that as recovery proceeds the movements become smoother. More specifically, this occurs mainly within the first 8 weeks post stroke, which is approximately the same time window as the improvement of motor control and capacity according to clinical assessments [2]. It is assumed that these improvements early after stroke are mainly the results of spontaneous neurological recovery [3]. This spontaneous recovery is however yet poorly understood. Studying movement quality during stroke recovery is vital to better understand the recovery process after stroke [3]. During the past two decades, over 20 different smoothness measures were used in research with stroke patients, yet there is no standardised measure for smoothness. This makes it hard to compare the different measures reported in literature. The purpose of this study is to make a step towards identifying a standardised measure for movement smoothness for stroke subjects. First a literature review was done to get an overview of all available measures for smoothness in reaching with stroke subjects. Subsequently, velocity profiles that mimic forward reaching movements were simulated. The behaviour of the metrics was studied while we varied different parameters in a reaching simulation, such as movement duration, movement distance, movement segmentation or added sinusoids and noise. Based on the findings in combination with the definition of smoothness, their suitability to measure smoothness is discussed. Results show that different measures can give contradicting outcomes, have a non-monotonic behaviour and are sensitive for noise. Furthermore, only three metrics out of 27 investigated, fully satisfied the definition of smoothness. From these simulations, it can be said that the correlation metric and spectral arc length are most suitable to determine the movement smoothness in reaching movements. This study could help identify standardised movement smoothness metrics for stroke subjects. [1] Balasubramanian, S., Melendez-Calderon, A., Roby-Brami, A., & Burdet, E. (2015). On the analysis of movement smoothness. Journal of neuroengineering and rehabilitation, 12(1), 112. [2] van Kordelaar, J., van Wegen, E., & Kwakkel, G. (2014). Impact of time on quality of motor control of the paretic upper limb after stroke. Archives of physical medicine and rehabilitation, 95(2), 338-344. [3] Buma, F., Kwakkel, G., & Ramsey, N. (2013). Understanding upper limb recovery after stroke. Restorative neurology and neuroscience, 31(6), 707-722.