Changes in locomotive rates during senior elite rugby league matches

Abstract

The aim of this study was to quantify the changes in locomotive rates across the duration of senior elite rugby league matches. A semi-automated image recognition system (ProZone 3, ProZone®, Leeds, England) was used to track the movements of 59 players from six teams during three competitive matches. The players were classified into one of four positional groups: props (n = 9), back row (n = 9), pivots (n = 14) or outside backs (n = 27). Players' movements were classified as low, high or very high intensity running and reported as locomotive rates (distance covered per minute played) for successive quarters of each match. Analysis of variance revealed that only the outside backs showed a significantly lower overall locomotive rate during the final quarter compared to the first (P < 0.05). However, locomotive rates for high and very high intensity running during the final quarter were significantly lower (P < 0.05) than the first quarter among outside backs, pivots and props despite no change in the rate of involvements in contact. On the basis of these findings, it is suggested that high and very high intensity running locomotive rates may be more affective methods of detecting fatigue during competitive matches than overall locomotive rate.     

Influence of vitamin D mushroom powder supplementation on exercise-induced muscle damage in vitamin D insufficient high school athletes

Abstract

Incidence of vitamin D deficiency is increasing worldwide. The purpose of this study was to determine if supplementation with vitamin D₂ from Portobello mushroom powder would enhance skeletal muscle function and attenuate exercise-induced muscle damage in low vitamin D status high school athletes. Participants were randomised to Portobello mushroom powder (600 IU/d vitamin D₂) or placebo for 6 weeks. Participants then completed a 1.5-h exercise session designed to induce skeletal muscle damage. Blood samples and measures of skeletal muscle function were taken pre-supplementation, post-supplementation/pre-exercise and post-exercise. Six weeks supplementation with vitamin D₂ increased serum 25(OH)D₂ by 9.9-fold and decreased serum 25(OH)D₃ by 28%. Changes in skeletal muscle function and circulating markers of skeletal muscle damage did not differ between groups. In conclusion, 600 IU/d vitamin D₂ increased 25(OH)D₂ with a concomitant decrease in 25(OD)D₃, with no effect on muscular function or exercise-induced muscle damage in high school athletes.     

The influence of intermittent high-intensity shuttle running and fluid ingestion on the performance of a soccer skill

The aim of this study was to examine the effect of intermittent high-intensity shuttle running and fluid ingestion on the performance of a soccer skill. Nine semi-professional soccer players volunteered to participate in the study. Their mean (± _sx ) age, body mass and maximal oxygen uptake were 20.2 ± 0.4 years, 73.2 ± 1.8 kg and 59.1 ± 1.3 ml·kg^-1 ·min^-1 respectively. The players were allocated to two randomly assigned trials: ingesting or abstaining from fluid intake during a 90 min intermittent exercise protocol (Loughborough Intermittent Shuttle Test:LIST).This test was designed to simulate the minimum physical demands faced by soccer players during a game. Before and immediately after performance of the test,the players completed a soccer skill test and a mental concentration test. Performance of the soccer skill test after the 'no-fluid' trial deteriorated by 5% (P ? 0.05),but was maintained during the fluid trial. Mean heart rate, perceived exertion, serum aldosterone, osmolality, sodium and cortisol responses during the test were higher (P ? 0.05) in the 'no-fluid' trial than in the fluid trial. The results of this study suggest that soccer players should consume fluid throughout a game to help prevent a deterioration in skill performance.     

Wikipedia,Critical Social Theory,and the Possibility of Rational Discourse 1

Information systems researchers that apply critical social perspectives frequently emphasize the potential for information technology to serve as a mechanism for increased rationalization, domination, and control. Such theorists often overlook or discount the liberating aspects of information systems. In this study, we apply the ideal of rational discourse developed by Jürgen Habermas to the phenomenon of Wikipedia in an effort to explore empirically the emancipatory potential of information systems. We contend that Wikipedia embodies an approximation of the necessary conditions for rational discourse. While several challenges persist, the example of Wikipedia illustrates the positive potential of information systems in supporting the emergence of more emancipatory forms of communication. The corresponding implications for researchers and design professionals alike are discussed.     

Handling pressures: analysing touch in American films about youth sport

This paper examines how films produced in the USA in the past 10 years and featuring the coaching of youth sport, represent the issue of touch during instruction and training. Touch in such films is figured in diverse ways ranging from pats of reassurance and hugs of congratulation to cuffs of disapprobation. Touch is also occasionally depicted differently, dependent upon the ethnicity and gender of the central characters in specific films. These distinctions are evaluated for what they reveal about the nuances of understandings of touch in film portrayals of sport education in American high schools. The difficulty of interpreting physical contact between coaches and athletes in these films, and what this reveals about the problem of policing touch in general in educational settings, is explored. Finally, the paper examines how the films expose the intricacy of tactile encounters in ways that challenge the judiciousness of risk-averse ‘no-touch’ policies and practices in sports coaching.     

A Tutorial on Centering in Cross-Sectional Two-Level Models

The primary purpose of this tutorial is to succinctly review some options for, and consequences of, centering Level 1 predictors in commonly applied cross-sectional two-level models. It is geared toward both practitioners and researchers. A general understanding of multilevel modeling is necessary prior to understanding the subtleties of centering decisions. A review of some high-quality journals within the broad discipline of exercise science provides evidence that multilevel modeling is used relatively infrequently in this field. Therefore, a secondary purpose is to introduce Measurement in Physical Education and Exercise Science readers to some core facets of multilevel modeling within the framework of this tutorial. A relevant dataset is used to demonstrate potential consequences of different centering decisions within a multilevel model. Depending on the model and the data, different centering decisions can exert non-trivial influence on the meaning of some model parameters, results from fitting the model, and subsequent conclusions.     

Effect of the coefficient of friction of a running surface on sprint time in a sled-towing exercise

This study investigated the effect of the coefficient of friction of a running surface on an athlete's sprint time in a sled-towing exercise. The coefficients of friction of four common sports surfaces (a synthetic athletics track, a natural grass rugby pitch, a 3G football pitch, and an artificial grass hockey pitch) were determined from the force required to tow a weighted sled across the surface. Timing gates were then used to measure the 30-m sprint time for six rugby players when towing a sled of varied weight across the surfaces. There were substantial differences between the coefficients of friction for the four surfaces (μ = 0.21–0.58), and in the sled-towing exercise the athlete's 30-m sprint time increased linearly with increasing sled weight. The hockey pitch (which had the lowest coefficient of friction) produced a substantially lower rate of increase in 30-m sprint time, but there were no significant differences between the other surfaces. The results indicate that although an athlete's sprint time in a sled-towing exercise is affected by the coefficient of friction of the surface, the relationship relationship between the athlete's rate of increase in 30-m sprint time and the coefficient of friction is more complex than expected.