Young Children’s Ability to Produce Valid and Relevant Counter-Arguments

In collaborative problem solving, children produce and evaluate arguments for proposals. We investigated whether 3- and 5-year-olds (N = 192) can produce and evaluate arguments against those arguments (i.e., counter-arguments). In Study 1, each child within a peer dyad was privately given a reason to prefer one over another solution to a task. One child, however, was given further information that would refute the reasoning of their partner. Five-year-olds, but not 3-year-olds, identified and produced valid and relevant counter-arguments. In Study 2, 3-year-olds were given discourse training (discourse that contrasted valid and invalid counter-arguments) and then given the same problem-solving tasks. After training, 3-year-olds could also identify and produce valid and relevant counter-arguments. Thus, participating in discourse about reasons facilitates children’s counter-argumentation.     

The kinematic differences between accurate and inaccurate squash forehand drives for athletes of different skill levels

ABSTRACT

To maintain the accuracy of squash shots under varying conditions, such as the oncoming ball’s velocity and trajectory, players must adjust their technique. Although differences in technique between skilled and less-skilled players have been studied, it is not yet understood how players vary their technique in a functional manner to maintain accuracy under varying conditions. This study compared 3-dimensional joint and racket kinematics and their variability between accurate and inaccurate squash forehand drives of 9 highly skilled and 9 less-skilled male athletes. During inaccurate shots, less-skilled players hit the ball with a more open racket, demonstrating a difference in this task-relevant parameter. No joint kinematic differences were found for accuracy for either group. Coordinated joint rotations at the elbow and wrist both displayed a “zeroing-in” effect, whereby movement variability was reduced from the initiation of propulsive joint rotation to a higher consistency at ball-impact; potentially highlighting the “functionality” of the variability prior to the impact that enabled consistent task-relevant parameters (racket orientation and velocity) under varying conditions. Further, highly skilled players demonstrated greater consistency of task-relevant parameters at impact than less-skilled players. These findings highlight the superior ability of highly skilled players to adjust their technique to achieve consistent task-relevant parameters and a successful shot.     

National Sporting Pastimes,Spectacles of Sporting Otherness and American Imaginings, 1880–1920

This discussion focuses on how the rise of America's national sporting pastimes, during the period 1880–1920, was inextricably tied to the ambitions and outpourings of American print capitalism and a concomitant congealing of a sense of modern American nationhood. In examining this thematic, we explicate the manner in which American national sporting audiences during the period 1880–1920 were variously constituted through discourses of national and ethnic sporting difference or Otherness. Hence, we examine the popular representation of turn of the century rodeo practices (as narrated through the spectacle of the western showman William Frederick ‘Buffalo Bill’ Cody's Wild West show productions), the position of early-twentieth-century American baseball in relation to other sporting cultures (graphically depicted by Albert Goodwill, or A.G., Spalding's promotional publications, specifically the 1911 America's National Game) and the national and ethnic differences discerned within the global sporting landscape more generally (explicated within the 1919 National Geographic article ‘The Geography of Games’). These performances and representations of ethnic and national sporting Otherness played an important role in re-inscribing and legitimating the (White European American) normative core of American sport culture (as manifest within and through the dominant practices of playing and/or spectating of football, baseball and basketball).     

Development of the Exercise Motives and Gains Inventory

There are existing measures of exercise motives (what people want from exercise), but corresponding measures of gains (what people get) are needed, because motives and gains could influence each other and together influence other variables. An exercise motives and gains inventory (EMGI) was developed by creating gains scales to complement existing Exercise Motivations Inventory 2 scales. Confirmatory factor analyses of EMGI items established that items reflected their intended constructs; and that motive and gain constructs were distinct. Exploratory structural equation modeling of EMGI scales established that the higher-order structures of motives and gains were somewhat different: Appearance motive was associated with weight management, whereas appearance gain was associated with health and fitness. Paired-sample t-tests established that gains were less than motives in some instances (ill-health avoidance, positive health), and greater in others (e.g., affiliation, challenge). The EMGI can be used to investigate the consequences and causes of motives and gains.     

Electronic reserves: copyright and permissions

Electronic reserves present a new service option for libraries to provide needed materials during hours that the library is not open and to user groups located some distance from library collections. Possible changes to current copyright law and publishers permissions policies have delayed the development of electronic reserves in many libraries. This paper reviews the current state of electronic reserves materials in the publishing and library communities and presents the results of a survey of publishers to determine permissions policies for electronic materials. Issues of concern to both libraries and publishers are discussed.     

Physiological and metabolic responses of wheelchair athletes in different racing classes to prolonged exercise

The aims of this study were to examine and compare selected physiological and metabolic responses of wheelchair athletes in two paraplegic racing classes [T3: n = 8 (lesion levels T1-T7; paraplegics); T4: n = 9 (lesion levels below T7; paraplegics)] to prolonged exercise. In addition, we describe the responses of three tetraplegic athletes [T2: n = 3 (lesion levels C6/C7: tetraplegics)]. Twenty athletes completed 90 min of exercise at 75% VO2peak on a motorized treadmill adapted for wheelchairs. The mean (+/- s) heart rates of the T3 and T4 racing classes were 165 +/- 2 and 172 +/- 6 beats.min-1, respectively. For the T4 racing class, heart rate gradually increased during the test (P < 0.05), whereas for the T3 racing class, heart rate reached a plateau after an initial increase. The mean heart rate of the tetraplegics was 114 +/- 3 beats.min-1. The T3 and T4 classes exhibited similar respiratory exchange ratios, plasma lactate and glucose concentrations throughout the test. For both the T3 and T4 racing class, free fatty acid, glycerol, ammonia, urea and potassium concentrations had increased from resting values by the end of the test (P < 0.05). In conclusion, the results of this study suggest that endurance-trained wheelchair athletes are able to maintain velocities equivalent to the same relative exercise intensity (75% VO2peak) for prolonged periods irrespective of lesion level.     

The effect of towing a range of relative resistances on sprint performance

The aim of this study was to compare sprint performance over 10 and 20?m when participants ran while towing resistances, weighing between 0 and 30% of body mass. The sample of 33 participants consisted of male rugby and soccer players (age 21.1?±?1.8 years, body mass 83.6?±?13.1?kg, height 1.82?±?0.1?m; mean?±?s). Each participant performed two sets of seven sprints over 20?m using a Latin rectangular design. The times were recorded at 10 and 20?m using electronic speed gates. The sprints of 13 players were video-recorded to allow calculation of stride length and frequency. For both sprints, a quadratic relationship was observed between sprint time and resistance as sprint time increased from 2.94?s to 3.80?s from 0 to 30% resistance. This relationship was statistically significant but considered not to be meaningful for performance because, over the range of resistances used in this study, the quadratic model was never more than 1% (in terms of sprint time) from the linear model. As resistance increased, the stride length shortened, with mean values of 1.63?±?0.13?m at 0% body mass and 1.33?±?0.13?m at 30% of body mass. There was no significant change in stride frequency with increasing resistance. The results show that in general there is an increase in sprint time with an increase in resistance. No particular resistance in the range tested (0?–?30%) can be recommended for practice.     

Energy turnover during 24 hours and 6 days of adventure racing

Abstract

Energy turnover was assessed in two conditions of mixed ultra-endurance exercise. In Study 1, energy expenditure and intake were measured in nine males in a laboratory over 24 h. In Study 2, energy expenditure was assessed in six males during an 800-km Adventure race (mean race time 152.5 h). Individual correlations between heart rate and oxygen uptake ([Vdot]O₂) were established during pre-tests when kayaking, cycling, and running. During exercise, energy expenditure was estimated from continuous heart rate recordings. Heart rate and [Vdot]O₂ were measured regularly during fixed cycling work rates to correct energy expenditure for drift in oxygen pulse. Mean energy expenditure was 18,050 ± 2,390 kcal (750 ± 100 kcal · h^?1) and 80,000 ± 18,000 kcal (500 ± 100 kcal · h^?1) in Study 1 and Study 2 respectively, which is higher than previously reported. Energy intake in Study 1 was 8,450 ± 1,160 kcal, resulting in an energy deficit of 9,590 ± 770 kcal. Body mass decreased in Study 1 (?2.3 ± 0.8 kg) but was unchanged in Study 2. Fat mass decreased in Study 2 (?2.3 ± 1.5 kg). In Study 1, muscle glycogen content decreased by only 60%. Adventure racing requires a high energy expenditure, with large inter-individual variation. A large energy deficit is caused by inadequate energy intake, possibly due to suppressed appetite and gastrointestinal problems. The oxygen pulse, comparing start to 12 h of exercise and beyond, increased by 10% and 5% in Study 1 and Study 2 respectively. Hence, estimations of energy expenditure from heart rate recordings should be corrected according to this drift.     

Bone mineral density and lean mass asymmetries are greater in cyclists than non-cyclists

ABSTRACT

Cyclists may be at greater risk of developing asymmetrical force and motion patterns than other ground-based athletes. However, functional asymmetries during cycling tend to be highly variable, making them difficult to assess. Dual-energy x-ray absorptiometry (DXA) measurements of areal bone mineral density (aBMD) and lean mass (LM) in the lower limbs may be a more sensitive and consistent method to identify asymmetries in cyclists. The goal of this study was to determine if competitive cyclists have greater levels of asymmetries in the lower body compared to non-cyclists using DXA. A secondary aim was to determine if aBMD and LM asymmetries change over the road cycling season. 17 competitive cyclists and 21 non-cyclist, healthy controls underwent DXA scans. Lower-body asymmetries were greater in cyclists compared to non-cyclists in aBMD and LM for all lower limb segments. However, these asymmetries did not tend to consistently favour a particular side, except for the pelvis having more LM on the dominant side. The were no longitudinal changes in aBMD or LM in the cyclists. Asymmetry analysis via DXA provides evidence that although functional asymmetries during cycling are variable, cyclists have increased lower body LM and aBMD asymmetries compared to non-cyclists.