The force–time profile of elite front crawl swimmers

Abstract

In this study, we used recently developed technology to determine the force–time profile of elite swimmers, which enabled coaches to make informed decisions on technique modifications. Eight elite male swimmers with a FINA (Federation Internationale de Natation) rank of 900+ completed five passive (streamline tow) and five net force (arms and leg swimming) trials. Three 50-Hz cameras were used to video each trial and were synchronized to the kinetic data output from a force-platform, upon which a motorized towing device was mounted. Passive and net force trials were completed at the participant's maximal front crawl swimming velocity. For the constant tow velocity, the net force profile was presented as a force–time graph, and the limitation of a constant velocity assumption was acknowledged. This allowed minimum and maximum net forces and arm symmetry to be identified. At a mean velocity of 1.92 ± 0.06 m · s^?1, the mean passive drag for the swimmers was 80.3 ± 4.0 N, and the mean net force was 262.4 ± 33.4 N. The mean location in the stroke cycle for minimum and maximum net force production was at 45% (insweep phase) and 75% (upsweep phase) of the stroke, respectively. This force–time profile also identified any stroke asymmetry.     

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.     

Participant Perceptions of Exercise Programs for Overweight Women

Abstract

Eighteen women participated in a research project involving two phases: (a) an interview regarding weight history and exercise patterns, and (b) a series of exercise sessions followed by discussions of participants' reactions to them. The data were analyzed using inductive analysis techniques, and results of the analysis were discussed with participants for collaborative validation of the interpretation. Profiles of selected participants and themes that emerged are described. The participants varied in age and body size and had diverse backgrounds, interests, and abilities, but their shared experience of social disapproval based on body size was shown to affect their perceptions of exercise programs and their decisions about participation.     

Free for All: A Case Study Examining Implementation Factors of One-to-One Device Programs

Despite significant investment in school one-to-one device programs, little is known about which aspects of program implementation work and why. Through a comparison of two implementation models, adopter-diffusion and saturation, and using existing data from the One Laptop per Child Australia laptop program, we explored how factors of implementation may affect device diffusion, learning and educational outcomes, and program sustainability in schools. In this article we argue that more focused research into implementation of one-to-one device programs, moving beyond comparisons of “devices versus without devices,” is needed to provide reliable data to inform future program funding and advance this area of research.     

Visualizing community: understanding narrative inquiry as action research

This article explores the experiences of students who used interactive learning material on handheld computers in a gallery to support their understanding and appreciation of artwork. The article considers the wider implications of using technology to change relationships between teacher, learners and subject matter, and attempts to offer positive and pragmatic recommendations about the implementation of new technology into established educational contexts. Research was undertaken as part of the ICT Test Bed Project, set up by the DfES (UK Department for Education and Science) and funded by Becta (British Education Communications Technology Agency). Initial findings from this project are likely to be of interest to those exploring how mobile technology can be used to support the Government’s wider agenda for educational reform and offer a practitioner’s critical perspective on the possibilities and challenges offered by their use.     

Numbers are Just Not Enough: A Critical Analysis of Race,Gender, and Sexuality in Elementary and Middle School Health Textbooks

Textbooks are a multimillion dollar publishing business in the United States. Even as 21st-century classrooms become more multimodal, digital and hardcopy textbooks remain a key feature of American education. Consequently, classroom textbooks have been shown to control knowledge dissemination across the content areas. In particular, health texts have been uniquely shown to communicate values that validate or marginalize students and encourage healthy or harmful activity. Thus, what textbook makers choose to include as worthy of study, and how they portray various groups of people with regard to race, gender, and sexuality has societal implications. Employing quantitative and qualitative content analysis methods, we analyzed 1,468 images across elementary and middle school health textbooks to examine the portrayal of race, gender, and sexuality. We found that, although gender and racial diversity are well-represented in texts, women and people of color were frequently portrayed in stereotypical roles. For example, girls were depicted daydreaming about heterosexual marriage. Furthermore, this analysis revealed limited representations of sexuality. Findings suggest that focusing on the numerical representation of marginalized groups is not enough to address issues of equity and power in classroom curricula. Instead, we argue, educators must consider the ways in which people are positioned in curricular materials, and ask if portrayals perpetuate or challenge traditional stereotypes.     

Kinematic analyses of seated throwing activities with and without an assistive pole

In Paralympic seated throwing events, the athlete can throw with and without an assistive pole. This study aimed to identify and compare performance-related kinematic variables associated with both seated throwing techniques. Twenty-nine non-disabled males (21.9 ± 2.6 years) performed 12 maximal throws using a 1-kg ball in two conditions (no-pole and pole). Automatic 3D-kinematic tracking (150 Hz) and temporal data were acquired. There was no significant difference between ball speeds at the point of release between conditions (no-pole = 12.8 ± 1.6 m/s vs. pole = 12.9 ± 1.5 m/s). There were four kinematic variables that were strongly correlated with ball speed when throwing with or without an assistive pole. These variables were elbow flexion at the start phase (pole r = .39 and no-pole r = .41), maximum shoulder external rotation angular velocity during the arm cocking phase (pole r = .42), maximum shoulder internal rotation angular velocity during the arm acceleration phase (pole r = .47), and should internal rotation angular velocity at the instant of ball release (pole r = .40). The pole clearly influenced the throwing technique with all four strongly correlated variables identified in this condition, compared to only one during the no-pole condition. When using the pole, participants produced significantly higher shoulder internal rotation angular velocities during the arm acceleration phase (pole = 367 ± 183°/s vs. no-pole = 275 ± 178°/s, p < .05) and at the instant of ball release (pole = 355 ± 115°/s vs. no-pole = 264 ± 120°/s, p < .05), compared to throwing without the pole. These findings have implications for the development of evidence-based classification systems in Paralympic seated throwing, and facilitate research that investigates the impact of impairment on seated throwing performance.