Push-off forces in elite short-track speed skating     

Eline van der Kruk  Marco M. Reijne  Bjorn de Laat  DirkJan Veeger 《Sports biomechanics / International Society of Biomechanics in Sports》2019,18(5):527-538

This study performed an analysis of the push-off forces of elite-short-track speed skaters using a new designed instrumented short-track speed skate with the aim to improve short-track skating performance. Four different skating strokes were distinguished for short-track speed skaters at speed. The strokes differed in stroke time, force level in both normal and lateral directions, and the centre of pressure (COP) on the blade. Within the homogeneous group of male elite speed skaters (N = 6), diversity of execution of the force patterns in the four phases of skating was evident, while skating at the same velocities. The male participants (N = 6) with a better personal record (PR) kept the COP more to the rear of their blades while hanging into the curve (r = 0.82, p < 0.05), leaving the curve (r = 0.86, p < 0.05), and entering the straight (r = 0.76, p < 0.10). Furthermore, the male skaters with a better PR showed a trend of a lower lateral peak force while entering the curve (r = 0.74, p < 0.10). Females showed a trend towards applying higher body weight normalised lateral forces than the males, while skating at imposed lower velocities.  相似文献   

Biomechanical analyses of synchronised swimming standard and contra-standard sculling     

Lara Elena Gomes  Vera Diogo  Flávio Antônio de Souza Castro  João Paulo Vilas-Boas  Ricardo J. Fernandes  Pedro Figueiredo 《Sports biomechanics / International Society of Biomechanics in Sports》2019,18(4):354-365

Synchronised swimming involves a variety of sculling movements essential for body support and propulsion but its study is scarce. We aimed to biomechanically compare standard and contra-standard sculling techniques, and to observe the relationship between measures. Six synchronised swimmers performed two, 30 s maximal intensity, fully tethered standard and contra-standard sculling motions. Kinetic and kinematic data were obtained using a load-cell and underwater cameras, respectively. Force decreased along both techniques’ bouts, but no differences in-between techniques were noted for any kinetic variables. Standard sculling presented a higher cycle rate and a lower elbow mean angle than the contra-standard sculling (2.4 ± 0.3 vs. 2.0 ± 0.2 cycles/s and 134.1 ± 5.8 and 141.5 ± 4.7°, p < 0.05). In the standard sculling, by removing and maintaining the variation between participants (r _w and r, respectively), the absolute mean force was directly related with cycle rate (r _w  = 0.60) and wrist angular velocity during flexion (r = 0.82), while in the contra-standard condition the force was inversely associated with wrist mean angle (r = ?0.95) and directly with hand speed (r _w  = 0.76), and elbow angular velocity (r _w  ≈ 0.60). Therefore, technique learning and training require different attention by coaches and swimmers.  相似文献   

Gender equality,sport and the United Nation’s system. 
A historical overview of the slow pace of progress     

Lilamani de Soysa 《Sport in Society》2019,22(11):1783-1800

Abstract

The history, milestones and (sluggish) progress towards gender equality within the interconnected movements of sport, international development and human rights are reflective of the broader feminist struggle. In this paper, we shall explore how key stakeholders, such as the United Nations Educational, Scientific and Cultural Organization (UNESCO), the (former) United Nations Office on Sport for Development and Peace (UNOSDP), the International Olympic Committee (IOC) and the International Working Group (IWG) on Women and Sport together with other women and sport organisations have been working to promote gender equality within and beyond sport. Despite decades of parallel or synchronized effort, critics contend that progress is slow and uneven, leaving generations of girls and women marginalized. In this article, we explain the progression towards a renewed initiative to create a UNESCO Global Observatory for Women, Sport, Physical Education and Physical Activity and discuss how the observatory should serve as a nexus of these collective movements by bringing advocacy, research and action together in one platform.  相似文献   

Democracy in Chains: The Deep History of the Radical Right's Stealth Plan for America Nancy MacLean. Viking, 2017.          下载免费PDF全文

Mel van Elteren 《Journal of American culture (Malden, Mass. : 2003)》2018,41(2):222-225

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Cosmopolitical zoo: a response to Tironi and Hermansen     

Marisol de la Cadena 《Journal of Cultural Economy》2018,11(4):351-353

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Travel purpose and expenditure patterns in city tourism: evidence from the Amsterdam Metropolitan Area     

Ruben van Loon  Jan Rouwendal 《Journal of Cultural Economics》2017,41(2):109-127

This study examines the expenditure patterns of urban tourists with different trip purposes including visiting cultural heritage. Expenditure categories include museums and theatres. We use a two-step approach, in which we first analyse the total daily amount of expenditure and then the budget shares of various categories. We make use of survey data collected for the Amsterdam Metropolitan Area, a large Western European city known for its rich cultural heritage and the semi-legalized use of cannabis. The econometric analysis shows that trip purposes are associated with substantial differences in total daily expenditure as well as on budget shares. However, the results also show that the activities undertaken by tourists are not limited to their (initial) trip purposes.  相似文献   

Validity of a portable force platform for assessing biomechanical parameters in three different tasks     

Ricardo Peterson Silveira  Pro Stergiou  Felipe P. Carpes  Flávio A. de S. Castro  Larry Katz  Darren J. Stefanyshyn 《Sports biomechanics / International Society of Biomechanics in Sports》2017,16(2):177-186

The aim of this study was to determine the precision and accuracy of the vertical and anterior–posterior force components of the portable PASCO PS-2142 force plate. Impulse, peak force, and time to peak force were assessed and compared to a gold standard force plate in three different tasks: vertical jump, forward jump, and sprint start. Two healthy male participants performed ten trials for each task, resulting in 60 trials. Data analyses revealed good precision and accuracy for the vertical component of the portable force plate, with relative bias and root mean square (RMS) error values nearly the same in all tasks for the impulse, time to peak force, and peak force parameters. Precision and accuracy of the anterior–posterior component were lower for the impulse and time to peak force, with relative bias and RMS error values nearly the same between tasks. Despite the lower precision and accuracy of the anterior–posterior component of the portable force plate, these errors were systematic, reflecting a good repeatability of the measure. In addition, all variables presented good agreement between the portable and gold standard platforms. Our results provide a good perspective for using the aforementioned portable force plate in sports and clinical biomechanics.  相似文献   

Getting in the game and getting on the move: family,the intergenerational contract and internal migration into football academies in Ghana     

Nienke van der Meij 《Sport in Society》2017,20(11):1580-1595

This article examines how young Ghanaian football players and their families actively engage with the processes and decision-making that lead them to migrate internally to academies. In particular, it explores whether moving to an academy is understood within the family setting as a precursor to international migration and as such, might feature as part of a broader household livelihood strategy. Drawing on empirical data collected during nine months of ethnographic fieldwork in Ghana, the article sheds light on the experiences of players who encounter the recruitment processes employed by academies and how these are shaped and informed by Ghanaian family arrangements and in particular the social norm of intergenerational reciprocity. By uncovering these wider dynamics, this study challenges the popular assumption that African youth and their family members unambiguously view academies as vehicles for international migration and future prosperity.  相似文献   

Effect of hand paddles and parachute on backstroke coordination and stroke parameters     

Thiago Telles  Renato Barroso  Pedro Figueiredo  Diego Fortes de Souza Salgueiro  João Paulo Vilas-Boas  Orival Andries Junior 《Journal of sports sciences》2017,35(9):906-911

Hand paddles and parachutes have been used in order to overload swimmers, and consequently increase the propulsive force generation in swimming. However, their use may affect not only kinematical parameters (average speed, stroke length and stroke rate), but also time gaps between propulsive phases, assessed through the index of coordination (IdC). The objective of this study was to assess the effects of hand paddles and parachute use, isolated or combined, on kinematical parameters and coordination. Eleven swimmers (backstroke 50-m time: 29.16 ± 1.43 s) performed four 15-m trials in a randomised order at maximal intensity: (1) without implements (FREE), (2) with hand paddles (HPD), (3) with parachute (PCH) and (4) with hand paddles plus parachute (HPD+PCH). All trials were video-recorded (60 Hz) in order to assess average speed, stroke rate, stroke length, five stroke phases and index of coordination. When average swimming speed was compared to FREE, it was lower in PCH and HPD+PCH, and higher in HPD. Stroke rate decreased in all overloaded trials compared to FREE. The use of hand paddles and parachute increased and decreased stroke length, respectively. In addition, propulsive phase duration was increased when hand paddles were used, and time gaps shifted towards zero (no time gap), especially when hand paddles were combined with parachute. It is conceivable that the combined use of hand paddles and parachute, once allowing overloading both propulsive and resistive forces, provides a specific stimulus to improve muscle strength and propulsive continuity.  相似文献   

The geometric curvature of the spine during the sirshasana,the yoga’s headstand     

Mário Hebling Campos  Nayane Martins Giraldi  Paulo Gentil  Claudio Andre Barbosa de Lira  Carlos A. Vieira  Marcelo Costa de Paula 《Journal of sports sciences》2017,35(12):1134-1141

This study analysed the behaviour of the geometric curvature of the spine during sirshasana. The position of dorsal retroreflective markers was computed via stereophotogrammetric analysis in six males and five females (29.4 ± 8.8 years, 63.0 ± 11.4 kg, 1.66 ± 0.08 m [average ± standard deviation]). The spinal points were projected onto the sagittal and frontal planes of the trunk, a polynomial was fitted to the data and the two-dimensional geometric curvature was quantified. The inferior lumbar lordosis decreased compared to the orthostatic position and gait, which may favour the posterior protrusion of the lumbar spinal nucleus pulposus in people with posterior herniation. The lateral deviation at the middle of the thoracic spine increases during sirshasana, which may reflect increased difficulties for postural control and spinal loads. It could be useful for promoting positive spinal structural and functional chronic adaptations for healthy participants, if the yoga programme is carefully planned and the spinal alignment is carefully monitored during a headstand. However, it may aggravate some spinal diseases, especially scoliosis.  相似文献