Quantifying stroke coordination during the breathing action in front-crawl swimming using an instantaneous net drag force profile

Abstract

This study used both an instantaneous net drag force profile and a symmetry timing to evaluate the effect of the breathing action on stroke coordination. Twenty elite swimmers completed a total of six randomised front-crawl towing trials: (i) three breathing trials and (ii) three non-breathing trials. The net drag force was measured using an assisted towing device mounted upon a Kistler force platform, and this equipment towed the swimmer at a constant speed. The net drag force profile was used to create a stroke symmetry index for each swimming trial. Analysis using the symmetry indices identified that the majority of participants demonstrated an asymmetrical instantaneous net drag force stroke profile in both the breathing and non-breathing conditions, despite no significant differences in the time from finger-tip entry to finger-tip exit. Within the breathing condition, the faster swimmers compared to the slower swimmers demonstrated a lesser percentage of overlap between stroke phases on their breathing stroke side. During the non-breathing condition, the faster participants compared to the slower swimmers recorded a reduction in the percentage of overlap between stroke phases and less duration in the underwater stroke on their breathing stroke side. This study identified that the majority of participants demonstrated an asymmetrical net drag force profile within both conditions; however, asymmetry was less prevalent when examining with only the timing symmetry index.     

Visual Search and Biological Motion Perception in Tennis

Purpose

The purposes of this study were to: (a) examine the effect of experience and goal constraints (speed, accuracy) on kicking patterns; (b) determine if effective striking mass was independent of ankle velocity at impact; and (c) determine the accuracy of kicks relative to independent factors.

Method

Twenty participants were recruited to kick at 3 different velocities with and without an accuracy requirement. Multivariate analysis of variance determined if relative timing of joint angular velocities changed during the kick. Chi-square analysis determined if calculated effective mass was independent of ankle velocity at impact. Analysis of variance (ANOVA) was used to examine differences in absolute constant error and variable error according to independent factors.

Results

Results indicated that experience and speed affect absolute timing of joint velocities with no changes in the relative timing of peak joint velocity across independent factors. Chi-square analysis indicated that calculated effective mass is not independent of ankle velocity. ANOVA indicated that experienced performers displayed less variability error than did inexperienced performers.

Conclusion

It was concluded that: (a) Experience, velocity, and accuracy do not affect the relative timing of kicks; (b) kickers trade ankle velocity at impact for greater effective striking mass and ball velocity; and (c) variability in ball placement is affected by experience.     

Reliability and construct validity of soccer skills tests that measure passing,shooting, and dribbling

Abstract

In this study, we examined the reliability and construct validity of new soccer skills tests. Twenty soccer players (10 professional and 10 recreational) repeated trials of passing, shooting, and dribbling skills on different days. Passing and shooting skills required players to kick a moving ball, delivered at constant speed, towards one of four randomly determined targets. Dribbling required players to negotiate seven cones over 20 m. Each trial consisted of 28 passes, 8 shots, and 10 dribbles. Ball speed, precision, and success were determined for all tests using video analysis. Systematic bias was small (<9% in all measures) and all outcome measures were similar between trials. Test–retest reliability statistics were as follows: ball speed (passing, shooting, dribbling; coefficient of variation [CV]: 6.5%, 6.9%, 2.4%; ratio limits of agreement [RLOA]: 0.958 ×/÷ 1.091, 0.990 ×/÷ 1.107, 0.993 ×/÷ 1.039), precision (passing, shooting, dribbling; CV: 10.0%, 23.5%, 4.6%; RLOA: 0.956 ×/÷ 1.147, 1.030 ×/÷ 1.356, 1.000 ×/÷ 1.068), and success (passing, shooting, dribbling; CV: 11.7%, 14.4%, 2.2%; RLOA: 1.017 ×/÷ 1.191, 0.913 ×/÷ 1.265, 0.996 ×/÷ 1.035). Professional players performed better than recreational players in at least one outcome measure for all skills. These findings demonstrate the reliability and validity of new soccer skill protocols.     

A New Perspective: The Common Factors Model as a Foundation for Social Work Practice Education

Foundation social work practice education is critical to the preparation of BSW practitioners for professional practice and the establishment of a theoretical and skill base upon which graduate students may build competencies in the advanced curriculum. Issues in the foundation practice curriculum may hinder this development. The common factors model holds promise as an organizing framework for foundation social work practice education. This model may help to resolve some key issues in social work and social work education, and may provide a useful, coherent, and empirical base for the foundation practice curriculum.     

Using Intensive Interaction to add to the palette of interactive possibilities in teacher–pupil communication

Intensive Interaction was introduced to a special developmental school in Melbourne, Australia. The school had previously used behavioural and skills‐based teaching approaches to underpin the teaching of students with severe/profound intellectual disabilities and autistic spectrum disorders. Video baselines of students involved in classroom interactions were taken before introducing the approach of Intensive Interaction to the school. Following a 30‐week period during which the approach was practised routinely in classrooms, further video records were made. These video records enabled comparison to be made against five indicators of student involvement. Professional development using video techniques and structured reflection was initiated with all involved staff. Increases in the student’s joint focus, positive affect and interactive involvement were noted. In addition to changes in the communicative involvement of the pupils, the practitioner’s communicative involvement was also noted to change.     

The dilemma of case‐based teaching and learning in science in Hong Kong: Students need it,want it,but may not value it

The paper reports a study for determining a suitable process for converting traditional surface science courses into case‐based learning ones in two universities in Hong Kong. In this preparative study, a set of baseline data was collected on the current level of students’ conceptual understanding and also students’ perceptions about the traditional courses. The student data (from 38 students) came from examination results, the Study Process Questionnaire, a course‐end survey and a focus group meeting; teachers also kept reflective journals. This set of baseline data revealed factors that both support and inhibit case‐based learning. On the one hand, students demonstrate a motivation to be able to solve practical problems in this field; on the other hand, they show an unwillingness to take up a personal responsibility for learning. This finding strengthens our resolve to take into account students’ expectations and beliefs in the implementation of case‐based teaching and learning.     

The canon in the classroom: Students' experiences of texts from other times

This paper examines the debate about the English literature canon in schools. It evaluates the importance of the canon in a 21st-century curriculum and considers its relevance to adolescent readers saturated in early 21st-century culture who have disparate identities and diverse backgrounds. The implications for teaching and learning of the chronological, social, cultural, and linguistic distance between pre-20th-century canonical texts and today's readers are examined in the light of the theoretical perspectives of Hans Robert Jauss and Wolfgang Iser. These perspectives are applied to findings from a recent 3-year longitudinal case study of 13-16-year-olds reading canonical texts and of the responsive teaching they experienced.