Velocity and acceleration before contact in the tackle during rugby union matches

Abstract

The velocity and acceleration at which the ball-carrier or tackler enters the tackle may contribute to winning the contest and prevailing injury free. Velocity and acceleration have been quantified in controlled settings, whereas in match-play it has been subjectively described. The purpose of this study was to determine the velocity and acceleration of the ball-carrier and tackler before contact during match-play in three competitions (Super 14, Varsity Cup, and Under-19 Currie Cup). Using a two-dimensional scaled version of the field, the velocity and acceleration of the ball-carrier and tackler were measured at every 0.1 s to contact for 0.5 s. For front-on tackles, a significant difference (P < 0.05) between the ball-carrier (4.6 ± 1 m · s^–1) and tackler (7.1 ± 3.5 m · s^–1) was found at the 0.5 s time to contact interval in the Varsity Cup. For side-on tackles, differences between the two opposing players were found at 0.5 s (ball-carrier: 4.6 ± 1.7 m · s^–1; tackler: 3.1 ± 1.2 m · s^–1) and 0.4 s (ball-carrier: 6.3 ± 2.3 m · s^–1; tackler: 3.7 ± 1.6 m · s^–1) at Under-19 level. After 0.4 s, no significant differences (P > 0.05) were evident. Also, the ball-carrier's velocity over the 0.5 s was relatively stable compared with that of the tackler. Results suggest that tacklers adjust their velocity to reach a suitable relative velocity before making contact with the ball-carrier.     

Tackle and ruck technique proficiency within academy and senior club rugby union

ABSTRACT

This study examined the validity of a tool that assesses tackle and ruck technique in training and established reference data for tackle, ball-carry and ruck technique at different levels of play in rugby union. One hundred and thirty-one amateur rugby union players; 37 senior, 51 first-grade academy and 43 second-grade academy players, participated in a two-on-two contact drill. The drill was filmed and the players’ tackle, ball-carry and ruck technique were assessed using standardized technical criteria. Senior level players scored significantly higher in all three assessments; tackle technique senior vs academy 1^st (p < 0.01, effect size (ES) = 0.7, moderate), senior vs academy 2^nd (p < 0.01, ES = 0.7, moderate); ball-carry technique senior vs academy 1^st (p < 0.01, ES = 0.6, moderate), senior vs academy 2^nd (p < 0.01, ES = 0.8, moderate); ruck technique senior vs academy 1^st (p < 0.01, ES = 0.7, moderate), senior vs academy 2^nd (p < 0.01, ES = 0.4, small). These findings emphasize the importance of developing contact technique to allow players to progress to higher levels, and provide validity to an assessment tool which can facilitate this process.     

Effectiveness of Rest,Abdominal Cold Packs,and Cold Showers in Relieving Fatigue

Abstract

The purpose of this study was to compare three methods of relieving fatigue between bouts of strenuous exercise—rest, abdominal cold packs, and cold showers. Fifteen subjects were used in the study; each subject participated in each of the three treatments, making a total of 45 measurements. The subjects ran on a treadmill which was set at 8 mph with a 10 percent elevation, until their pulse rates reached 180 beats per minute. One of the three treatments was then applied for 10 min., after which the subjects engaged in a second treadmill run until heart rates reached 180 beats per minute. The time of the second treadmill run was the main criterion measure.

A complete randomized block design was used to test the differences among the three treatments for statistical significance. The Newman-Keuls sequential range test was employed to test differences between all possible pairs of treatment. Abdominal cold packs proved to be the most effective treatment, with the cold shower second and rest third.     

Nutritional strategies for promoting fat utilization and delaying the onset of fatigue during prolonged exercise

Carbohydrate ingestion before and during endurance exercise delays the onset of fatigue (reduced power output). Therefore, endurance athletes are recommended to ingest diets high in carbohydrate (70% of total energy) during competition and training. However, increasing the availability of plasma free fatty acids has been shown to slow the rate of muscle and liver glycogen depletion by promoting the utilization of fat. Ingested fat, in the form of long-chain (C 16-22 ) triacylglycerols, is largely unavailable during acute exercise, but medium-chain (C 8-10 ) triacylglycerols are rapidly absorbed and oxidized. We have shown that the ingestion of medium-chain triacylglycerols in combination with carbohydrate spares muscle carbohydrate stores during 2 h of submaximal (< 70% VO 2 peak) cycling exercise, and improves 40 km time-trial performance. These data suggest that by combining carbohydrate and medium-chain triacylglycerols as a pre-exercise supplement and as a nutritional supplement during exercise, fat oxidation will be enhanced, and endogenous carbohydrate will be spared. We have also examined the chronic metabolic adaptations and effects on substrate utilization and endurance performance when athletes ingest a diet that is high in fat (> 70% by energy). Dietary fat adaptation for a period of at least 2-4 weeks has resulted in a nearly two-fold increase in resistance to fatigue during prolonged, low- to moderate-intensity cycling (< 70% VO 2 peak). Moreover, preliminary studies suggest that mean cycling 20 km time-trial performance following prolonged submaximal exercise is enhanced by 80 s after dietary fat adaptation and 3 days of carbohydrate loading. Thus the relative contribution of fuel substrate to prolonged endurance activity may be modified by training, pre-exercise feeding, habitual diet, or by artificially altering the hormonal milieu or the availability of circulating fuels. The time course and dose-response of these effects on maximizing the oxidative contribution of fat for exercise metabolism and in exercise performance have not been systematically studied during moderate- to high-intensity exercise in humans.     

Baumgartner's Modified Pull-Up Test For Male and Female Elementary School Aged Children

Abstract

Nineteen college men and women (aged 18–23 yrs, × = 21.1) were studied to ascertain the force-time components of a rapid maximal voluntary isometric contraction (MVC) for ankle dorsiflexors, knee extensors, elbow flexors, wrist flexors and hand grip. Standardized isometric strength testing protocol was used. After a practice period subjects were instructed to make an MVC without jerking and as quickly as possible, for each of the muscle actions noted above. Force readings were taken from a load cell assembly through an analogue-to-digital converter and analyzed to yield time values for MVC, 3/4 MVC, 1/2 MVC, and 1/4 MVC. The results indicated significant differences (p < .01) between the responses of the men and women, with the women reaching full MVC more rapidly than the men. Also, there were significant differences among the five muscle groups tested, with the wrist flexor muscle group developing MVC most quickly, while the knee extensors took the longest time to full MVC. Based upon these data it may be concluded that the time to full MVC differs between men and women, and also that the time to full MVC differs among the five muscle groups tested in this experiment.     

From students to teachers: using surveys to build a culture of evidence and inquiry

In an effort to make decisions about teacher education policy and practice that were informed by research and evidence, participants in Boston College's ‘Teachers for a New Era’ Evidence Team (http://www.teachersforanewera.org) designed a portfolio of assessments and studies. This article describes one project in the portfolio – a series of surveys that trace teacher candidates' experiences over time and track shifts in these experiences as respondents progress from students during the pre‐service period to teachers in the first few years of work in the profession. The article illustrates how various constituencies in the teacher education programme and the larger university used survey data to guide practice, shape policies, and raise new questions about the curriculum, relationships with schools, and the performance of teachers and their pupils. The article argues that these surveys helped to create a new ‘culture of evidence and inquiry’ within which decisions about local policy and practice were made in the teacher preparation programme and the larger university.     

世界著名沉船事件之一玛丽号

1545年“玛丽·罗斯”号在海港沉没。然而, 50年前,她却是亨利八世舰队的骄傲。     

Evaluating the effects of faculty development: theoretical framework and empirical implementation

ABSTRACT

This article implements a systemic framework to evaluate the long-term effects of a program characterized by a SoTL approach and a hybrid learning environment. The importance of the difference between the perception of long-term effects on individual professional development on the one hand and the development of collective practices on the other, is interpreted with reference to certain shortcomings of the faculty development program’s learning design and its non-alignment with institutional practices. Based on this in-depth research, concrete ways to take account of the complexity of faculty development programs are proposed, both for research into and development of such programs and their impact at individual and institutional levels.     

Relationships between students' meaningful learning orientation and their understanding of genetics topics

This study explored factors predicting the extent to which high school students (N = 140) acquired meaningful understanding of the biological topics of meiosis, the Punnett-square method, and the relationships between these topics. This study (a) examined mental modeling as a technique for measuring students' meaningful understanding of the topics, (b) measured students' predisposed, generalized tendency to learn meaningfully (meaningful learning orientation), (c) determined the extent to which students' meaningful learning orientation predicted meaningful understanding beyond that predicted by aptitude and achievement motivation, (d) experimentally tested two instructional treatments (relationships presented to students, relationships generated by students), (e) explored the relationships of meaningful learning orientation, prior knowledge, instructional treatment, and all interactions of these variables in predicting meaningful understanding. The results of correlations and multiple regressions indicated that meaningful learning orientation contributed to students' attainment of meaningful understanding independent of aptitude and achievement motivation. Meaningful learning orientation and prior knowledge interacted in unique ways for each topic to predict students' attainment of meaningful understanding. Instructional treatment had relatively little relationship to students' acquisition of meaningful understanding, except for learners midrange between meaningful and rote. These findings imply that a meaningful learning approach among students may be important, perhaps as much or more than aptitude and achievement motivation, for their acquisition of interrelated, meaningful understandings of science.