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Alejandro Bastida Castillo Carlos D. Gómez Carmona Ernesto De la cruz sánchez José Pino Ortega 《European Journal of Sport Science》2018,18(4):450-457
There is interest in the accuracy and inter-unit reliability of position-tracking systems to monitor players. Research into this technology, although relatively recent, has grown exponentially in the last years, and it is difficult to find professional team sport that does not use Global Positioning System (GPS) technology at least. The aim of this study is to know the accuracy of both GPS-based and Ultra Wide Band (UWB)-based systems on a soccer field and their inter- and intra-unit reliability. A secondary aim is to compare them for practical applications in sport science. Following institutional ethical approval and familiarization, 10 healthy and well-trained former soccer players (20?±?1.6 years, 1.76?±?0.08?cm, and 69.5?±?9.8?kg) performed three course tests: (i) linear course, (ii) circular course, and (iii) a zig–zag course, all using UWB and GPS technologies. The average speed and distance covered were compared with timing gates and the real distance as references. The UWB technology showed better accuracy (bias: 0.57–5.85%), test–retest reliability (%TEM: 1.19), and inter-unit reliability (bias: 0.18) in determining distance covered than the GPS technology (bias: 0.69–6.05%; %TEM: 1.47; bias: 0.25) overall. Also, UWB showed better results (bias: 0.09; ICC: 0.979; bias: 0.01) for mean velocity measurement than GPS (bias: 0.18; ICC: 0.951; bias: 0.03). 相似文献
426.
Effective force and economy of triathletes and cyclists 总被引:1,自引:0,他引:1
Candotti CT Ribeiro J Soares DP De Oliveira AR Loss JF Guimarães AC 《Sports biomechanics / International Society of Biomechanics in Sports》2007,6(1):31-43
The effective force applied on the crank, the index of pedalling effectiveness, and the economy of movement at 60, 75, 90, and 105 rev/min cadences were examined in nine cyclists and eight triathletes. Tests were performed on two days. Maximal oxygen uptake was measured and the second ventilatory threshold was estimated on day 1 using a stationary bicycle. On day 2, the four different cadences were tested at about 5% below the second ventilatory threshold. A strain gauge instrumented clip-less pedal mounted on the bicycle enabled us to measure the normal and tangential forces exerted on the pedal, while the pedal and crank angles were monitored with the aid of a video system. Based on this information, the effective force and the index of pedalling effectiveness were calculated. Cyclists produced significantly more effective force and a higher index of pedalling effectiveness at 60 and 75 rev/min and were significantly more economic at all cadences than triathletes. The significant and positive correlation between effective force and economy at all cadences suggests that improvement of the effective force would reflect on economy. 相似文献
427.
Irene Esteban-Millat Francisco J. Martínez-López Juan Carlos Gázquez-Abad Alejandro Alegret 《Interactive Learning Environments》2018,26(7):895-910
This study advances the understanding of the process by which students accept and use e-learning environments. This is a key aspect in studying the online behaviour of students, as it directly influences their conduct in their capacity as users of learning products. To address the lack of empirical data on the adoption of this type of learning environment, we present and validate a model of the phenomenon. The study considers the utilitarian aspects included in the technology acceptance model (TAM) and also an aspect of intrinsic motivation for an individual, flow, to enhancing the explanatory power of the models presented.
Based on a sample of 2,574 students, structural equation modelling is used to test the model. We identify the effect of flow on perceived ease of use, perceived usefulness and on the actual usage of the e-learning environment, demonstrating the importance of this factor as a complement to the components of the TAM. 相似文献
428.
The principal contribution of this note is to avoid the parametric resonance effect and attenuate the payload oscillations in an overhead-crane system subject to periodic variations in the base support. Considering an appropriate sliding output with relative degree one, we present the sliding mode control design based on the Super-Twisting Algorithm (STA), ensuring finite time convergence to the desired sliding surface for the linear periodic system with Lipschitz continuous matched and unmatched uncertainties bounded together by their gradients by known functions. The suggested approach also provides chattering phenomenon attenuation. Obtained results are verified experimentally. 相似文献
429.
Carlos Balsalobre-Fernández Mark Glaister Richard Anthony Lockey 《Journal of sports sciences》2015,33(15):1574-1579
The purpose of this investigation was to analyse the concurrent validity and reliability of an iPhone app (called: My Jump) for measuring vertical jump performance. Twenty recreationally active healthy men (age: 22.1 ± 3.6 years) completed five maximal countermovement jumps, which were evaluated using a force platform (time in the air method) and a specially designed iPhone app. My jump was developed to calculate the jump height from flight time using the high-speed video recording facility on the iPhone 5 s. Jump heights of the 100 jumps measured, for both devices, were compared using the intraclass correlation coefficient, Pearson product moment correlation coefficient (r), Cronbach’s alpha (α), coefficient of variation and Bland–Altman plots. There was almost perfect agreement between the force platform and My Jump for the countermovement jump height (intraclass correlation coefficient = 0.997, P < 0.001; Bland–Altman bias = 1.1 ± 0.5 cm, P < 0.001). In comparison with the force platform, My Jump showed good validity for the CMJ height (r = 0.995, P < 0.001). The results of the present study showed that CMJ height can be easily, accurately and reliably evaluated using a specially developed iPhone 5 s app. 相似文献
430.
Maria Salinas Maite López-Garrigós Emilio Flores Ana Santo-Quiles Mercedes Gutierrez Javier Lugo Rosa Lillo Carlos Leiva-Salinas 《Biochemia medica : ?asopis Hrvatskoga dru?tva medicinskih biokemi?ara / HDMB》2015,25(1):49-56