Measurement of three-dimensional hand kinematics during swimming with a motion capture system: a feasibility study

Current trends in swimming biomechanics are focused on accurate measurements. Nowadays, reliable calibration methods have been proposed to reach an accuracy of about 1 mm on rigid structure. But the question remains about the final accuracy for three-dimensional hand kinematics measurement during the underwater phase of front crawl swimming. Furthermore, most research is based on manual tracking with two or more cameras. In this paper we propose a protocol to acquire three-dimensional hand kinematics when swimming in a specific pool with a motion analysis system behind windows. Results highlight the benefits of using such a system in terms of accuracy and feasibility: the time allowed for post-processing is ten times lower and the quantified improved accuracy is better than with manual tracking.     

Anticipatory postural adjustments during cutting manoeuvres in football and their consequences for knee injury risk

Abstract

Anticipatory postural adjustments (APAs), i.e. preparatory positioning of the head, the trunk and the foot, are essential to initiate cutting manoeuvres during football games. The aim of the present study was to determine how APA strategies during cutting manoeuvres are influenced by a reduction of the time available to prepare the movement.

Thirteen football players performed different cutting tasks, with directions of cutting either known prior to the task or indicated by a light signal occurring 850, 600 or 500 ms before ground contact.

With less time available to prepare the cutting manoeuvre, the head was less orientated towards the cutting direction (P = 0.033) and the trunk was even more rotated in the opposite direction (P = 0.002), while the foot placement was not significantly influenced. Moreover, the induced higher lateral trunk flexion correlated with the increased knee abduction moment (r = 0.41; P = 0.009).

Increasing lateral trunk flexion is the main strategy used to successfully perform a cutting manoeuvre when less time is available to prepare the movement. However, higher lateral trunk flexion was associated with an increased knee abduction moment and therefore an increased knee injury risk. Reducing lateral trunk flexion during cutting manoeuvres should be part of training programs seeking the optimisation of APAs.     

Learning whom not to trust across early and middle adolescence: A longitudinal neuroimaging study to trusting behavior involving an uncooperative other

Longitudinal changes in trusting behavior across adolescence and their neural correlates were examined. Neural regions of interest (ROIs) included the medial prefrontal cortex (mPFC), dorsal anterior cingulate cortex (dACC), left anterior insula (AI), bilateral ventral striatum (VS), and right dorsal striatum (DS). Participants (wave 1 age: M = 12.90) played the investor in a Trust Game with an uncooperative trustee three times (1-year interval). Analyses included 77 primarily Dutch participants (33 females). Participants decreased their investments with wave. Furthermore, activity was heightened in mPFC, dACC, and DS during investment and repayment, and in right VS (investment) and AI (repayment). Finally, DS activity during repayment increased with wave. These findings highlight early–middle adolescence as an important period for developing sensitivity to uncooperative behavior.     

Effects of school choice on the margin: The cream is already skimmed

Critics of school choice argue that cream-skimming will worsen outcomes for those left behind in public schools. Since “high ability” families may have already sorted themselves out of the schools in question, this paper will examine whether existing within-school heterogeneity leaves any scope for cream-skimming to operate. It asks, “given the current level of within-school heterogeneity, how strong would peer effects have to be to significantly worsen outcomes for those left behind?” In order for cream-skimming to lower math test scores by one half-year's progress, the peer effect would have to be as strong as increasing class sizes by 8–20 students, or cutting per-student funding by $400–2000. These results indicate that current levels of within-school heterogeneity are so low that peer effects would have to be unrealistically strong to give cream-skimming any bite.     

Not Your Usual Maths Course: critical mathematics education for adults

This article describes an action research project that investigated which features of critical theory were useful for teaching everyday mathematics in an evening course for adults. Paulo Freire's philosophy of education and Jürgen Habermas’ theory of knowledge interests are among the main influences on exponents of critical mathematics education such as Ole Skovsmose and Marilyn Frankenstein. Through the use of dialogical processes and critical reflection, students engage in social and political issues in their lives or communities and, as a result of their increased consciousness and mathematical learning, take “transforming action”. This study highlights the value of learning in a positive environment, through dialogical processes and critical questioning. Participants of the study were able to overcome barriers to learning mathematics; engage in everyday issues involving mathematics; and make changes to the way they dealt with mathematics, as a result of increased critical consciousness.     

Effective conditioning of female soccer players

We compared the efficacy of three physical conditioning programmes provided over a 12 week period (24 h in total) on selected anthropometric and physical fitness parameters in female soccer players. Two of the groups received physical conditioning training in accordance with speed, agility and quickness (SAQ); one group used specialized resistance and speed development SAQ equipment (equipment group; n = 12), while the other group used traditional soccer coaching equipment (non-equipment group; n = 12). A third group received their regular fitness sessions (active control group; n = 12). All three interventions decreased (P < 0.001) the participants' body mass index (-3.7%) and fat percentage (-1.7%), and increased their flexibility (+14.7%) and maximal aerobic capacity (VO2max) (+18.4%). The participants in the equipment and non-equipment conditioning groups showed significantly (P < 0.005) greater benefits from their training programme than those in the active control group by performing significantly better on the sprint to fatigue (-11.6% for both the equipment and non-equipment groups versus -6.2% for the active control group), 25 m sprint (-4.4% vs -0.7%), left (-4.5% vs -1.0%) and right (-4.0% vs -1.4%) side agility, and vertical (+18.5% vs +4.8%) and horizontal (+7.7% vs +1.6%) power tests. Some of these differences in improvements in physical fitness between the equipment and non-equipment conditioning groups on the one hand and the active control group on the other hand were probably due to the specificity of the training programmes. It was concluded that SAQ training principles appear to be effective in the physical conditioning of female soccer players. Moreover, these principles can be implemented during whole team training sessions without the need for specialized SAQ equipment. Finally, more research is required to establish the relationship between physical fitness and soccer performance as well as the principles underlying the improvements seen through the implementation of SAQ training programmes.     

Understanding the consequences of victory amongst sport spectators: The mediating role of BIRGing

Prior work on the relationships between team identification and spectators’ reactions to one's team victory has largely neglected the potential effects of mediating variables. In this research, we proposed that the process of Basking in Reflected Glory [BIRGing – the tendency to reduce the distance between oneself and one's team; Cialdini, R. B., Bordon, R. J., Thorne, A., Walker, M. R., Freeman, S., &; Sloan, L. R. (1976). Basking in reflected glory: Three (football) field studies. Journal of Personality and Social Psychology, 34, 366–375] would lead spectators to almost take ownership of victories and share its benefits, thereby impacting their sense of national belonging in a positive manner. To this end, participants (N?=?73) were asked to watch an edited video clip showing a victory of the French national rugby team playing against South Africa. As expected, results revealed that BIRGing mediated the relationship between team identification and one's sense of national belonging. In closing, a number of implications are discussed along with future research avenues pertaining to the sport spectatorship literature.     

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