Heart rate,blood lactate concentration and estimated energy expenditure in a semi-professional rugby league team during a match: a case study

The aim of this study was to examine heart rate, blood lactate concentration and estimated energy expenditure during a competitive rugby league match. Seventeen well-trained rugby league players (age, 23.9 +/- 4.1 years; VO2max, 57.9 +/- 3.6 ml x kg(-1) x min(-1); height, 1.82 +/- 0.06 m; body mass, 90.2 +/- 9.6 kg; mean +/- s) participated in the study. Heart rate was recorded continuously throughout the match using Polar Vantage NV recordable heart rate monitors. Blood lactate samples (n = 102) were taken before the match, after the warm-up, at random stoppages in play, at half time and immediately after the match. Estimated energy expenditure during the match was calculated from the heart rate-VO2 relationship determined in laboratory tests. The mean team heart rate (n = 15) was not significantly different between halves (167 +/- 9 vs 165 +/- 11 beats x min(-1)). Mean match intensity was 81.1 +/- 5.8% VO2max. Mean match blood lactate concentration was 7.2 +/- 2.5 mmol x l(-1), with concentrations for the first half (8.4 +/- 1.8 mmol x l(-1)) being significantly higher than those for the second half (5.9 +/- 2.5 mmol x l(-1)) (P<0.05). Energy expenditure was approximately 7.9 MJ. These results demonstrate that semi-professional rugby league is a highly aerobic game with a considerable anaerobic component requiring high lactate tolerance. Training programmes should reflect these demands placed on players during competitive match-play.     

Colour-based rigid body tracking using three-dimensional graphics models

This paper introduces the first stage of a new model-based approach to three-dimensional (3D) human movement tracking. A ‘generate-and-test’ matching procedure was adopted by matching rendered images of a 3D computer graphics model of the human body to target images of rigid body motion. The set of pixels to be compared were just those corresponding to the model of the body in the rendered images. The matching criterion to optimize model position and orientation was based on the minimisation of the RGB (red-green-blue) colour difference between generated model images and associated target images. The method was able to track synthetic image sequences of a half twisting somersault accurately with root-mean-square (rms) errors of less than 5 mm and 0.3∘ for position and orientation estimates respectively. The suitability of the proposed approach for rigid body motion tracking was supported by additional tracking experiments on video image sequences of ‘wooden cross’ trajectories. Comparisons of tracked estimates against manual digitizing estimates returned relatively small rms difference values on both side somersault and twisting somersault movements. The proposed approach has the potential to track video images of a human torso using a rigid body model and hence to track articulated movements by successively adding segments to the model in a hierarchical manner.     

Comparing Factors Related to Reading Comprehension in Adolescents Who Speak English as a First (L1) or Second (L2) Language

This study examined factors related to reading comprehension in adolescents who spoke English as a first language (L1) and English as a second language (L2). Measures of decoding, vocabulary knowledge, and reading comprehension were administered to 31 L1 and 44 L2 speakers. English L2 adolescents scored significantly lower than their L1 peers on all measures. Factor analyses produced different configurations of variables for each group. For L1 learners, measures of decoding and vocabulary were separate factors but were one factor for English L2 learners. For the L1 learners, it was only the measure of vocabulary that was a significant predictor of reading comprehension. For L2 learners, decoding, vocabulary, and the interaction of decoding and vocabulary were all significant predictors of reading comprehension. Relations among these variables in adolescents who are beginning to learn English as an L2 are explored.     

Extending students’ mathematical thinking during whole-group discussions

Studies show that extending students’ mathematical thinking during whole-group discussions is a challenging undertaking. To better understand what extending student thinking looks like and how teachers’ mathematical knowledge for teaching (MKT) supports teachers in their efforts to extend student thinking, the teaching of six experienced elementary school teachers was explored. During group discussions, all six teachers created opportunities for extending student thinking about important mathematical ideas and solution methods. Findings on the nature of these episodes include identification of individual instructional actions and the ways in which teachers’ MKT was connected to these actions.