Effects of load mass carried in a backpack upon respiratory muscle fatigue

Purpose: The purpose of this study was to investigate whether loads carried in a backpack, with a load mass ranging from 0 to 20?kg, causes respiratory muscle fatigue. Methods: Eight males performed four randomised load carriage (LC) trials comprising 60?min walking at 6.5?km?h^?1 wearing a backpack of either 0 (LC₀), 10 (LC₁₀), 15 (LC₁₅) or 20?kg (LC₂₀). Inspiratory (P_Imax) and expiratory (P_Emax) mouth pressures were assessed prior to and immediately following each trial. Pulmonary gas exchange, heart rate (HR), blood lactate and glucose concentration and perceptual responses were recorded during the first and final 60?s of each trial. Results: Group mean P_Imax and P_Emax were unchanged following 60-min load carriage in all conditions (p?>?.05). There was an increase over time in pulmonary gas exchange, HR and perceptions of effort relative to baseline measures during each trial (p?p?>?.05). Conclusions: These findings indicate that sub-maximal walking with no load or carrying 10, 15 or 20?kg in a backpack for up to 60?min does not cause respiratory muscle fatigue despite causing an increase in physiological, metabolic and perceptual parameters.     

Manchester and the Emergence of an Association Football Culture, 1840–1880: An Alternative Viewpoint

This paper provides a critique of the article by Gary James and Dave Day on ‘The Emergence of an Association Football Culture in Manchester, 1840–1884', published in Sport in History. We suggest an alternative interpretation of Manchester's football history during this period, arguing that Association football was a minor form of football in a city largely dominated by the rugby code. Furthermore, by employing an artificial construct of Manchester the authors have produced the wrong answer to the wrong question. Rather than trying to prove that Manchester developed an important Association football culture, we suggest they ought to have addressed the question of why such a culture did not exist. The contribution to the development of Association football of three isolated ‘transitory’ clubs in a city as large as Manchester is certainly not ‘substantial’. Subsequently, James and Day also fail to exploit fully their evidence for early football in the Manchester area by omitting to relate this properly to the much wider ongoing debate surrounding the origins of football. Conversely, there is ample evidence that ‘substantial’ Association football developments actually occurred in East Lancashire, centred on Bolton, Blackburn and Darwen, developments that are scarcely noted in James and Day's account.     

Interpretation and application of the offside law by expert assistant referees: Perception of spatial positions in complex dynamic events on and off the field

Abstract

Baldo et al. (2002 Baldo, M. V. C., Ranvaud, R. D. and Morya, E. 2002. Flag errors in soccer games: The flash-lag effect brought to real life. Perception, 31: 1205–1210. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar]) and Helsen et al. (2006 Helsen, W., Gilis, B. and Weston, M. 2006. Errors in judging “offside” in association football: Test of the optical error versus the perceptual flash-lag hypothesis. Journal of Sports Sciences, 24: 521–528. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]) considered the flash-lag effect to explain errors made by assistant referees when judging offside in association football. The main aims of the present study were as follows: (1) to determine whether the flash-lag effect emerges in offside situations on the field of play or off the field when presented as computer animations or as video footage of real-life matches; (2) to examine offside decision-making errors in two standards of assistant referee – international FIFA and Belgian national referees. The results support the flash-lag hypothesis in several ways. First, both the FIFA and Belgian assistant referees were more likely to make errors by raising their flag when they had to assess offside situations on the field of play and when presented as three-a-side computer animations. Second, more flag errors were made when the defender moved in the opposite direction to that of the attacker. Third, the strategy of raising the flag in case of doubt was not observed when an interpretation of the offside law had to be made about the involvement of play of an attacker. Future research is needed to examine the extent to which on- and off-the-field training sessions can be used as training tools to improve offside decision-making.     

The good,the bad and the wiki: Evaluating student‐generated content for collaborative learning

This paper explores the potential for wiki‐type open architecture software to promote and support collaborative learning through the use of student‐created content. It delineates some of the affordances and constraints of wiki software as an open architecture that has the potential to facilitate collaborative learning through community‐focused enquiry. It seeks to promote debate in this key area of development, and highlights some recent key contributions to the developing discourse on social software in what has been termed ‘the architecture of participation’.     

Establishing open and critical discourses in the science classroom: Reflecting on initial difficulties

This paper presents a reflective account of a science teacher’s endeavours to use the referent of critical constructivism to transform her pedagogical practices. The context of her action research was a Year 10 Bioethics unit taught at an independent girls’ school in Perth, Western Australia. Students were provided with opportunities to engage in open and critical discourses; many did, but a few were unwilling to participate in accordance with the teacher’s intentions. We illustrate the disruptive influence of these “dissident” students and explore the reasons for their unwillingness to suspend their disbelief in a new way of knowing (and of being) that involves a radical change in the role of language in the classroom. We conclude with recommendations for epistemological pluralism and the careful use of critical discourse for re-negotiating teaching and learning roles and creating conditions for open discourse to flourish.     

English Premiership Academy knee injuries: lessons from a 5 year study

This study addresses the epidemiology of knee injuries in adolescent males. Data were collected prospectively from 41 Premiership soccer academies over a 5 year period from July 2000 to June 2005. A total of 12,306 player seasons were registered in the U9 to the U16 age categories with a total of 1750 recordable injuries specific to the knee joint. There was a mean incidence of 0.71 (95% confidence interval ± 0.05) knee injuries per player per year, and a median of 17 (inter-quartile range 9-38) training days and 2 (inter-quartile range 1-4) matches missed per knee injury. Knee injuries were found to be most common in the 14-16 year age group. Six hundred and nine (35% of total) injuries were classed as severe resulting in more than 28 days' absence. Injuries were more likely to be sustained in a competitive or match-play environment (862 or 52%) than in training (796 or 48%), and a non-contact mechanism was implicated in 823 (55%) of recorded cases. Peaks in injury numbers were seen in early season and subsequent to the winter break. Sprain was the most common diagnosis recorded, with the medial collateral ligament affected in 23% of all knee injuries. Knee injuries are common in elite youth footballers. In this uninsured age group, it could be argued that earlier medical intervention may reduce long-term damage to the immature skeleton.     

Epistemological commitments in the learning of science: Examples from dynamics

An observation schedule was developed to find out if girls have less interaction with teachers than boys in physics lessons. The schedule was intended to be used by a single observer with pencil and paper. It was also intended that the analysis of the data collected should be as straightforward as possible, without the need for video or audio playback, as all interpretation of the classroom interaction takes place during the live observation.

It was found that boys received more ‘public’ interactions concerning the cognitive content of their physics lessons than girls. This seemed to be related to the higher incidence of boys calling out answers, rather than the teachers initiating more interactions with the boys.     

Differential scanning calorimetry: Fundamental overview

This paper discusses the fundamentals of Differential Scanning Calorimetry (DSC) including functions and outputs of a Differential Scanning Calorimeter along with common uses in academia and industry.     

Physiological demands of top-class soccer refereeing in relation to physical capacity: effect of intense intermittent exercise training

To examine the activity profile and physiological demands of top-class soccer refereeing, we performed computerized time-motion analyses and measured the heart rate and blood lactate concentration of 27 referees during 43 competitive matches in the two top Danish leagues. To relate match performance to physical capacity and training, several physiological tests were performed before and after intermittent exercise training. Total distance covered was 10.07 - 0.13 km (mean - s x ), of which 1.67 - 0.08 km was high-intensity running. High-intensity running and backwards running decreased (P ? 0.05) in the second half. Mean heart rate was 162 - 2 beats· min -1 (85 - 1% of maximal heart rate) and the mean blood lactate concentration was 4.9 - 0.3 (range 1.7-14.0) mmol·l -1 . The amount of high-intensity running during a match was related to the Yo-Yo intermittent recovery test ( r 2 = 0.57; P ? 0.05) and the 12 min run ( r 2 = 0.21; P ? 0.05). After intermittent training ( n = 8), distance covered during high-intensity running was greater (2.06 - 0.13 vs 1.69 - 0.08 km; P ? 0.05) and mean heart rate was lower (159 - 1 vs 164 - 2 beats· min -1 ; P ? 0.05) than before training. The results of the present study demonstrate that: (1) top-class soccer referees have significant aerobic energy expenditure throughout a game and episodes of considerable anaerobic energy turnover; (2) the ability to perform high-intensity running is reduced towards the end of matches; (3) the Yo-Yo intermittent recovery test can be used to evaluate referees' match performance; and (4) intense intermittent exercise training improves referees' performance capacity during a game.