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%).
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In wheelchair sports, there is an increasing need to monitor mechanical power in the field. When rolling resistance is known, inertial measurement units (IMUs) can be used to determine mechanical power. However, upper body (i.e., trunk) motion affects the mass distribution between the small front and large rear wheels, thus affecting rolling resistance. Therefore, drag tests – which are commonly used to estimate rolling resistance – may not be valid. The aim of this study was to investigate the influence of trunk motion on mechanical power estimates in hand-rim wheelchair propulsion by comparing instantaneous resistance-based power loss with drag test-based power loss. Experiments were performed with no, moderate and full trunk motion during wheelchair propulsion. During these experiments, power loss was determined based on 1) the instantaneous rolling resistance and 2) based on the rolling resistance determined from drag tests (thus neglecting the effects of trunk motion). Results showed that power loss values of the two methods were similar when no trunk motion was present (mean difference [MD] of 0.6 1.6 %). However, drag test-based power loss was underestimated up to −3.3 2.3 % MD when the extent of trunk motion increased (r = 0.85). To conclude, during wheelchair propulsion with active trunk motion, neglecting the effects of trunk motion leads to an underestimated mechanical power of 1 to 6 % when it is estimated with drag test values. Depending on the required accuracy and the amount of trunk motion in the target group, the influence of trunk motion on power estimates should be corrected for.
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An important performance determinant in wheelchair sports is the power exchanged between the athletewheelchair combination and the environment, in short, mechanical power. Inertial measurement units (IMUs) might be used to estimate the exchanged mechanical power during wheelchair sports practice. However, to validly apply IMUs for mechanical power assessment in wheelchair sports, a well-founded and unambiguous theoretical framework is required that follows the dynamics of manual wheelchair propulsion. Therefore, this research has two goals. First, to present a theoretical framework that supports the use of IMUs to estimate power output via power balance equations. Second, to demonstrate the use of the IMU-based power estimates during wheelchair propulsion based on experimental data. Mechanical power during straight-line wheelchair propulsion on a treadmill was estimated using a wheel mounted IMU and was subsequently compared to optical motion capture data serving as a reference. IMU-based power was calculated from rolling resistance (estimated from drag tests) and change in kinetic energy (estimated using wheelchair velocity and wheelchair acceleration). The results reveal no significant difference between reference power values and the proposed IMU-based power (1.8% mean difference, N.S.). As the estimated rolling resistance shows a 0.9–1.7% underestimation, over time, IMU-based power will be slightly underestimated as well. To conclude, the theoretical framework and the resulting IMU model seems to provide acceptable estimates of mechanical power during straight-line wheelchair propulsion in wheelchair (sports) practice, and it is an important first step towards feasible power estimations in all wheelchair sports situations.
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Dit artikel ligt momenteel ter beoordeling bij een reviewer van het European Journal of Sport Sciences.
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Quantifying measures of physical loading has been an essential part of performance monitoring within elite able-bodied sport, facilitated through advancing innovative technology. In wheelchair court sports (WCS) the inter-individual variability of physical impairments in the athletes increases the necessity for accurate load and performance measurements, while at the same time standard load monitoring methods (e.g. heart-rate) often fail in this group and dedicated WCS performance measurement methods are scarce. The objective of this review was to provide practitioners and researchers with an overview and recommendations to underpin the selection of suitable technologies for a variety of load and performance monitoring purposes specific to WCS. This review explored the different technologies that have been used for load and performance monitoring in WCS. During structured field testing, magnetic switch based devices, optical encoders and laser systems have all been used to monitor linear aspects of performance. However, movement in WCS is multidirectional, hence accelerations, decelerations and rotational performance and their impact on physiological responses and determination of skill level, is also of interest. Subsequently both for structured field testing as well as match-play and training, inertial measurement units mounted on wheels and frame have emerged as an accurate and practical option for quantifying linear and non-linear movements. In conclusion, each method has its place in load and performance measurement, yet inertial sensors seem most versatile and accurate. However, to add context to load and performance metrics, position-based acquisition devices such as automated image-based processing or local positioning systems are required.
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Er zijn de achterliggende jaren veel innovatieve ontwikkelingen geweest op het gebied van het lassen. Een deel van deze ontwikkelingen is mogelijk gemaakt door de beschikbaarheid van nieuwe stroombronnen. Het zijn vooral de snelle ontwikkelingen in de vermogenselektronica die hierbij een cruciale rol spelen. De ontwikkelingen in de elektronica zijn gebaseerd op het steeds sneller maken en verdergaande miniaturisering van de elektronische componenten. Dit is een algemene trend in ons dagelijks bestaan, die misschien wel het meest zichtbaar is bij de ontwikkeling van Personal Computers: vooral sneller en kleiner van afmetingen. De ontwikkelingen op het gebied van computers en vooral van het hart 'de microprocessor' zijn indertijd voorspeld door Moore en vastgelegd in een zogenaamde "Wet van Moore" (De Wet van Moore stelt dat het aantal transistors op een computerchip door de technologische vooruitgang elke 24 maanden verdubbelt). Voorlopig gaat de Wet van Moore nog steeds op en het is de verwachting dat aan het huidige tempo van deze ontwikkelingen voorlopig nog geen einde is gekomen. Alle apparatuur waarin dit soort 'computerchips' toepassing vinden (dus ook in onze stroombronnen) volgen deze snelle ontwikkelingen.
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Innovation is not what it was in the 20th century; the classic century of R & D based innovation. The nature of innovation is changing, only in part because different technologies dominate innovation. This paper identifies three main societal trends that are of major importance for strategic management of innovation in industry and for government industrial- and technology policies. These trends are: - Growing complexity - Globalisation - Citizen participation As a result, innovation strategy and technology policies cannot be determined by ad hoc technology push and market pull factors popping up. Strategic planning, not just of products and technologies but also of sites and alliances becomes increasingly important. Transparency and stakeholder dialogue require new competencies of the technology manager.
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Fortuna Sittard wordt sinds twee jaar in financieel en bestuurlijk opzicht geleid door Isitan Gün, een Turkse econoom op wiens cv wordt vermeld dat hij na een carrière in de financiële wereld belandde bij de topclub Galatasaray S.K. In het kielzog van deze Turkse ondernemer streek nog een aantal Turkse zakenlieden in Zuid-Limburg neer, onder wie de 25-jarige accountant die club en geldschieter aan elkaar koppelde en nu verantwoordelijk is voor de boekhouding, en een nieuwe directeur voetbal en scout spelers. Interessant is ook de aanwezigheid van de (voormalige?) eigenaar van het Turkse spelersagentschap PMH Management & Consulting. Voormalig staat hier met opzet tussen haakjes en met een vraagteken vermeld. Volgens Gün is de bewuste zaakwaarnemer namelijk al tijden niet meer bij het agentschap betrokken, maar uit informatie van de Turkse Kamer van Koophandel blijkt dat zijn naam nog steeds wordt onder de kop ‘Management & Staf’ wordt vermeld. Het feit dat hierboven de spelerscarrousel bij Roda en de mogelijke betrokkenheid van een spelersmakelaar bij Fortuna expliciet zijn genoemd, heeft een reden. Ondanks het feit dat bij beide clubs geen aanwijzingen bestaan dat de investeringen die zijn gedaan een wederrechtelijke herkomst hebben, is uit de literatuur bekend dat bij het witwassen van crimineel geld in het professionele voetbal de transfer van spelers een belangrijk vehikel is. In dit artikel staat deze thematiek centraal. Na een korte uiteenzetting van de redenen waarom het professionele voetbal zich bij uitstek leent voor het witwassen van crimineel vermogen via de transfermarkt, wordt ingezoomd op de vraag welke mogelijkheden bestaan om dammen tegen dit fenomeen op te werpen. Daarbij wordt in het bijzonder aangehaakt bij de maatregelen die van lidstaten worden verwacht in het kader van de inmiddels vijfde anti-witwasrichtlijn. Bediscussieerd zal worden welke mogelijkheden de in Nederland bij witwasbestrijding en -preventie betrokken partijen hebben om malafide praktijken in het voetbal tegen te gaan en in hoeverre en op welke wijze zij daarvan gebruikmaken. LinkedIn: https://www.linkedin.com/in/pietersteenwijk/
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Touristification of consumption spaces describes a process in which retail and hospitality businesses adapt to the tourist demand, eroding place attachment among local residents. While this is an important cause of resistance to tourism, little is known about the mechanisms that drive or mediate this process. We address this gap by interviewing entrepreneurs in Amsterdam. We found three distinct areas in close proximity where entrepreneurs responded to increasing tourism in markedly different ways; by crowd-pleasing, niche-playing and gentrifying. The resulting microgeographies of touristification of consumption spaces have not only been overlooked in literature, but also in urban policies. This causes a mismatch between the more generic, city-wide regulation and the highly differentiated effects of tourism on consumption spaces.
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The aim of this explorative study was to determine the key inertial measurement unit-based wheelchair mobility performance components during a wheelchair tennis match. A total of 64 wheelchair tennis matches were played by 15 wheelchair tennis players (6 women, 5 men, 4 juniors). All individual tennis wheelchairs were instrumented with inertial measurement units, two on the axes of the wheels and one on the frame. A total of 48 potentially relevant wheelchair tennis outcome variables were initially extracted from the sensor signals, based on previous wheelchair sports research and the input of wheelchair tennis experts (coaches, embedded scientists). A principal component analysis was used to reduce this set of variables to the most relevant outcomes for wheelchair tennis mobility. Results showed that wheelchair mobility performance in wheelchair tennis can be described by six components: rotations to racket side in (1) curves and (2) turns; (3) linear accelerations; (4) rotations to non-racket side in (4) turns and (5) curves; and finally, (6) linear velocities. One or two outcome variables per component were selected to allow an easier interpretation of results. These key outcome variables can be used to adequately describe the wheelchair mobility performance aspect of wheelchair tennis during a wheelchair tennis match and can be monitored during training.
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