Accurate assessment of rolling resistance is important for wheelchair propulsion analyses. However, the commonly used drag and deceleration tests are reported to underestimate rolling resistance up to 6% due to the (neglected) influence of trunk motion. The first aim of this study was to investigate the accuracy of using trunk and wheelchair kinematics to predict the intra-cyclical load distribution, more particularly front wheel loading, during hand-rim wheelchair propulsion. Secondly, the study compared the accuracy of rolling resistance determined from the predicted load distribution with the accuracy of drag test-based rolling resistance. Twenty-five able-bodied participants performed hand-rim wheelchair propulsion on a large motor-driven treadmill. During the treadmill sessions, front wheel load was assessed with load pins to determine the load distribution between the front and rear wheels. Accordingly, a machine learning model was trained to predict front wheel load from kinematic data. Based on two inertial sensors (attached to the trunk and wheelchair) and the machine learning model, front wheel load was predicted with a mean absolute error (MAE) of 3.8% (or 1.8 kg). Rolling resistance determined from the predicted load distribution (MAE: 0.9%, mean error (ME): 0.1%) was more accurate than drag test-based rolling resistance (MAE: 2.5%, ME: −1.3%).
Introduction: To determine if athletes with coordination impairment (CI) can continue playing wheelchair rugby (WR), while an evidence-based classification system, including impairment tests for CI is not yet available. This is a defensible practise if they show similar activity limitations as athletes with other eligible impairment types (OI) within the same sports class. Methods: Standardised activities were measured in 58 elite WR athletes; 14 with CI and 44 with OI. Wheelchair activities consisted of 20-meter sprint, 12-meter sprint with full stop, intermittent sprint (3-meter sprint, stop, 3-meter sprint, stop, 6-meter sprint with full stop), sprint-curve-slalom-curve, turn on the spot 180°, turn on the spot 90°, stop, turn 90°in the same direction, X-test (short circuit with sharp turns) without the ball. Ball activities consisted of maximal throwing distance, precision throwing short (25% of maximum throw) and long (75% of maximal throw) distance and X-test with the ball (pick-up the ball and dribble whilst pushing). Descriptive statistics were used and Spearman’s Rank correlation was assessed for athletes with CI and OI for each outcome measure. Differences between athletes with CI and OI were assessed using a Mann-Whitney U test. Results: Most activities showed a high correlation with the athlete class in both athletes with CI and athletes with OI. Furthermore, outcome measures of athletes with CI overlapped with athletes with OI in the same sports class for all activities. There was a trend for worse performance in athletes with CI in turn on the spot 90°, stop, turn 90°in the same direction, the short distance one handed precision throw (P 0.11)and in the X-test with the ball (P 0.10). Discussion: Despite the current lack of evidence based impairment tests for CI, it is a defensible practise to not exclude athletes with CI from WR with the current classification system. The trends for differences in performance that were found can support athletes and coaches in optimising performance of athletes with CI.
In wheelchair sports, the use of Inertial Measurement Units (IMUs) has proven to be one of the most accessible ways for ambulatory measurement of wheelchair kinematics. A three-IMU configuration, with one IMU attached to the wheelchair frame and two IMUs on each wheel axle, has previously shown accurate results and is considered optimal for accuracy. Configurations with fewer sensors reduce costs and could enhance usability, but may be less accurate. The aim of this study was to quantify the decline in accuracy for measuring wheelchair kinematics with a stepwise sensor reduction. Ten differently skilled participants performed a series of wheelchair sport specific tests while their performance was simultaneously measured with IMUs and an optical motion capture system which served as reference. Subsequently, both a one-IMU and a two-IMU configuration were validated and the accuracy of the two approaches was compared for linear and angular wheelchair velocity. Results revealed that the one-IMU approach show a mean absolute error (MAE) of 0.10 m/s for absolute linear velocity and a MAE of 8.1◦/s for wheelchair angular velocity when compared with the reference system. The twoIMU approach showed similar differences for absolute linear wheelchair velocity (MAE 0.10 m/s), and smaller differences for angular velocity (MAE 3.0◦/s). Overall, a lower number of IMUs used in the configuration resulted in a lower accuracy of wheelchair kinematics. Based on the results of this study, choices regarding the number of IMUs can be made depending on the aim, required accuracy and resources available.
De prestatie in rolstoelsporten wordt voor een groot deel bepaald door de ‘Wheelchair Mobility Performance’ (WMP), de prestatiemaat voor de atleet-rolstoel combinatie. Binnen het project ‘de perfecte sportrolstoel’ is een methode ontwikkeld ‘de Wheelchair Mobility Performance Monitor’ (WMPM) om mobility performance te meten en uit te drukken in een aantal objectief goed te kwantificeren uitkomstmaten zoals snelheid, versnelling en wendbaarheid. Deze maten geven inzicht in de relatie tussen atleet, rolstoel en sport. Door middel van de WMPM is het mogelijk inzicht te verkrijgen in de fysieke eisen die in rolstoelsport gesteld worden, feedback te geven aan atleten en coaches, het evalueren van training en wedstrijden en het kan rolstoelexperts ondersteunen in het optimaliseren van de rolstoel. Binnen het RAAK-project is de WMPM ontwikkeld en ingezet als onderzoekstool bij verschillende rolstoelsporten. De WMPM biedt echter ook goede kansen voor het gebruik door coaches in de beroepspraktijk. Echter, de WMPM is nog niet eenvoudig toepasbaar voor zelfstandig gebruik door coaches en atleten voor het continue monitoren van prestaties. Met deze aanvraag willen we de implementatie van de WMPM in de beroepspraktijk faciliteren, door het verder ontwikkelen van het systeem naar een praktijkapplicatie en door NL-team coaches en embedded scientists in de rolstoelsporten tennis en basketbal op weg te helpen in het gebruik. Daarbij zal er zowel aandacht zijn voor de technische vervolmaking, maar vooral ook voor de implementatie van het systeem in de sportpraktijk. Samen met coaches, atleten en onderzoekers zal een live feedback tool naar een voor de praktijk toegankelijk platform worden omgezet, zodat deze direct inzetbaar is in de voorbereiding op de Paralympische spelen van 2020 en verder. Hierbij zullen onderzoekers en studenten van meerdere opleidingen als ICT en media en mechatronica betrokken worden.
