Circles on pommel horse with a suspended aid: spatio-temporal characteristics

A suspended aid is popular for learning circles and for refining circle technique on pommel horse. The aim of this study was to investigate the effect of using a suspended aid on the biomechanical characteristics of circles. This first study focused specifically on the spatio-temporal characteristics of circles. Eighteen gymnasts performed three sets of 10 circles with and without a suspended aid on a pommel horse under which two force plates were set. Three-dimensional coordinates were acquired using 13 Qualisys motion tracking cameras operating at 100 Hz. The results showed that circles with the aid were characterised by a smaller body flexion angle, a greater shoulder angle, a greater ankle circle diameter, earlier hand releases, and a longer total duration. In contrast, the body lateral flexion angle, the arm-leaning angle, and the shoulder circle diameter remained relatively similar to circles without the aid. It was confirmed that circles with the aid actually appeared to be more desirable in terms of the movement amplitude. In this sense, a suspended aid could function as spotting, which is often used for a progression to learn gymnastics skills and to let gymnasts experience a desired movement pattern.     

Men's and women's childhood sexual abuse and victimization in adult partner relationships: A study of risk factors

Objectives(1) Document the prevalence of childhood sexual abuse (CSA), childhood physical assault, psychological, physical and sexual intimate partner violence (IPV) in a nationally representative sample. (2) Assess the predictive value of CSA and other characteristics of the respondents and their current partners as potential risk factors for IPV. (3) Assess factors predicting IPV in adulthood in a subsample of women reporting CSA.MethodsThe role of CSA as a risk factor for adult IPV was examined using data from the 1999 Canadian General Social Survey. A national stratified sample of 9170 women and 7823 men with current or previous partners were interviewed by telephone by Statistics Canada. Multiple logistic regressions were used.ResultsCSA consistently predicted IPV for women and men, although this relationship was weaker for men. Age, current marital status and limitations due to physical or mental condition or chronic illness were also predictors of IPV for men and women. For women reporting CSA, age (being younger) or being in a more recent relationship and being limited due to either physical, mental conditions or chronic illness were predictive of adult victimization.ConclusionsThese findings indicate that CSA is associated with a greater risk of IPV beyond sociodemographic risk factors.Practice implicationsTo prevent IPV in women already at risk because of CSA, education about protective strategies seems important, particularly for women with physical or mental limitations, in the beginning stages of intimate relationships or for women with partners who drink excessively.     

Aerodynamic drag in cycling: methods of assessment

When cycling on level ground at a speed greater than 14 m/s, aerodynamic drag is the most important resistive force. About 90% of the total mechanical power output is necessary to overcome it. Aerodynamic drag is mainly affected by the effective frontal area which is the product of the projected frontal area and the coefficient of drag. The effective frontal area represents the position of the cyclist on the bicycle and the aerodynamics of the cyclist-bicycle system in this position. In order to optimise performance, estimation of these parameters is necessary. The aim of this study is to describe and comment on the methods used during the last 30 years for the evaluation of the effective frontal area and the projected frontal area in cycling, in both laboratory and actual conditions. Most of the field methods are not expensive and can be realised with few materials, providing valid results in comparison with the reference method in aerodynamics, the wind tunnel. Finally, knowledge of these parameters can be useful in practice or to create theoretical models of cycling performance.     

The effects of stride technique and pitch location on slo-pitch batting

In slo-pitch softball, the ball is delivered in an arc trajectory with a moderate velocity; hence, batters have time to adjust their stride technique based on the pitched ball location. The purpose of this study was to examine the influence of stride technique and pitched ball location on the mechanics of slo-pitch batting. A two-way ANOVA of two locations of pitch (inside and outside) x three strides (open, parallel, and closed) repeated measure study was conducted in this study. The results showed that the stride technique and pitched ball location did not have a consistent impact on the participants across different batting conditions, so the study recommends slo-pitch batters to explore different stride techniques when striking the ball. Further, to better understand the generalizability of the findings, the results indicated that participants were quite homogeneous as a group. Hence, coaches and educators may apply the findings from this study to other players with similar skill level.     

Electronic platforms and two-sided markets: A side-switching analysis

We define electronic platforms as two-sided markets in which two groups of agents – sellers and buyers – can switch from one side of the market to the other. Using a duopoly model, we interpret equilibrium fees and profits in terms of rewards and penalties, relative to the equilibrium without side-switching. We establish that if the group with the highest side-switching probability has the lowest externality parameter, platforms make more profit with side-switching. It is also shown that agents' heterogeneity is favorable to platform profitability.     

A Case Study in the Measurement of Educational Efficiency in Open and Distance Learning

Open and distance learning (ODL) gives learners control of the time, place, and pace of learning, often being characterized as flexible learning. However, this flexibility goes hand‐in‐hand with procrastination and non‐completion. As a result, the efficiency of the educational process is of importance to ODL providers, government funding agencies, and learners themselves. Despite its importance, measuring efficiency in ODL is problematic. This article presents a case study in measuring educational efficiency using a method which reflects the special characteristics of ODL. The article concludes with a discussion of the wider applicability of the measurement method in the context of lifelong learning.     

Perception of boys’ mother-son social interactions: Disruptive boys’ behaviors and involvement in learning tasks

This study focused on the relationship between social perception and children’s involvement in learning tasks. The interaction between disruptive boys’ (n=32) perception of the competence attributed to them by their mother, the mother’s behavior (verbal and physical intrusion) and the child’s involvement in learning tasks was observed in a laboratory setting. Boys were asked to solve easy and difficult tasks on a personnal computer under the supervision of their mother. Observations of mother-child interactions showed that disruptive boys with a negative perception of the competence attributed to them by their mother, were less involved in the difficult task than boys who had a positive perception. Mothers of the boys with a negative perception showed more verbal intrusions in the easy task and more physical intrusions in the difficult task than the mothers of boys with a positive perception. Mothers’ verbal intrusion, physical intrusion and boys’ involvement in the task discriminated 75% of the boys with a negative social perception. These results seem to indicate that disruptive boys do not constitute an homogeneous group and that a significant variation in their involvement in a learning task is related to their perception of the competence attributed to them by their mother.