Classroom Climate,Cardiac Vagal Tone,and Inhibitory Control: Links to Focused Attention in First Graders

The present study aimed to investigate the role of classroom climate and self‐regulation in terms of cardiac vagal tone and inhibitory control in primary school students' focused attention. A combination of direct and indirect measures was used to assess classroom climate, sustained and selective attention, and inattention behaviors among 62 first graders. We also registered students' cardiac vagal tone at rest and their levels of inhibitory control in a reaction time task. A single underlying factor combining sustained and selective attention as well as (the lack of) inattention behaviors accounted for students' focused attention. A regression analysis revealed that classroom climate, cardiac vagal tone, and inhibitory control interacted to explain first graders' focused attention. In classrooms with a negative climate, high levels of inhibitory control attenuated the negative effect of low cardiac vagal tone on students' ability to remain focused during classroom activities. Implications for theory and practice are discussed.     

Contribution of uncertainty in estimation of active drag using assisted towing method in front crawl swimming

Active drag force in swimming can be calculated from a function of five different variables: swim velocity, tow velocity, belt force, power output and exponent of velocity. The accuracy of the drag force value is dependent on the accuracy of each variable, and on the contribution of each variable to drag estimation. To calculate uncertainty in drag value, first the derivatives of the active drag equation with respect to each variable were obtained. Second, these were multiplied by the uncertainty of that variable. Twelve national age and open level swimmers were recruited to complete four free swimming and five active drag trials. The uncertainties for the free and the tow swim velocities, and for the belt force, contributed approximately 5–6% and 2–3% error, respectively, in calculation of drag. The result of the uncertainty of the velocity exponent (1.8–2.6) indicated a contribution of about 6% error in active drag. The contribution of unequal power output showed that if a power changed 7.5% between conditions, it would lead to about 30% error in calculated drag. Consequently, if a swimmer did not maintain constant power output between conditions, there would be substantial errors in the calculation of active drag.     

The validity and reliability of a novel indoor player tracking system for use within wheelchair court sports

Abstract

The aim of the current study was to investigate the validity and reliability of a radio frequency-based system for accurately tracking athlete movement within wheelchair court sports. Four wheelchair-specific tests were devised to assess the system during (i) static measurements; (ii) incremental fixed speeds; (iii) peak speeds; and (iv) multidirectional movements. During each test, three sampling frequencies (4, 8 and 16 Hz) were compared to a criterion method for distance, mean and peak speeds. Absolute static error remained between 0.19 and 0.32 m across the session. Distance values (test (ii)) showed greatest relative error in 4 Hz tags (1.3%), with significantly lower errors seen in higher frequency tags (<1.0%). Relative peak speed errors of <2.0% (test (iii)) were revealed across all sampling frequencies in relation to the criterion (4.00 ± 0.09 m · sˉ¹). Results showed 8 and 16 Hz sampling frequencies displayed the closest-to-criterion values, whilst intra-tag reliability never exceeded 2.0% coefficient of variation (% CV) during peak speed detection. Minimal relative distance errors (<0.2%) were also seen across sampling frequencies (test (iv)). To conclude, the indoor tracking system is deemed an acceptable tool for tracking wheelchair court match play using a tag frequency of 8 or 16 Hz.     

A physiological and biomechanical comparison of over-ground,treadmill and ergometer wheelchair propulsion

Abstract

The purpose of the study was to determine which laboratory-based modality provides the most valid physiological and biomechanical representation of over-ground sports wheelchair propulsion. Fifteen able-bodied participants with previous experience of wheelchair propulsion performed a 3-minute exercise trial at three speeds (4, 6 and 8 km ? h^–1) in three testing modalities over separate sessions: (i) over-ground propulsion on a wooden sprung surface; (ii) wheelchair ergometer propulsion; (iii) treadmill propulsion at four different gradients (0%, 0.7%, 1.0% and 1,3%). A 0.7% treadmill gradient was shown to best reflect the oxygen uptake (7.3 to 9.1% coefficient of variation (CV)) and heart rate responses (4.9 to 6.4% CV) of over-ground propulsion at 4 and 6 km ? h^–1. A 1.0% treadmill gradient provided a more valid representation of oxygen uptake during over-ground propulsion at 8 km ? h^–1 (8.6% CV). Physiological demand was significantly underestimated in the 0% gradient and overestimated in the 1.3% gradient and wheelchair ergometer trials compared to over-ground trials (P<0.05). No laboratory-based modality provided a valid representation of the forces applied during OG (≥ 18.4% CV). To conclude, a 0.7% treadmill gradient is recommended to replicate over-ground wheelchair propulsion at lower speeds (4 and 6 km ? h^–1) whereas a 1.0% gradient may be more suitable at 8 km ? h^–1.     

Validation of Weinbach's and Hanavan's Models for Computation of Physical Properties of the Forearm

Abstract

The purpose of the present study was to validate the Weinbach and the Hanavan models for the determinations of the forearm volume and center of mass. The study was conducted using 20 forearms from six male and four female cadavers. Results from the present investigation indicate that Weinbach's model is more accurate than Hanavan's model in estimating forearm volume and center of mass. The relative location of the center of mass and the center of volume was also investigated with the Weinbach model and these centers were found to coincide. The Hanavan model should be used only in the cases where the shape of the forearm closely resembles that of a truncated cone.     

Development and Validation of a Method for Determining Tridimensional Angular Displacements with Special Applications to Ice Hockey Motions

Abstract

Tridimensional angular displacements of the skates were determined with a single cinecamera used in conjunction with two orthogonal rods attached to the rear part of the skater's boots. The method was based on the commutative law with the imposed restrictions that two of the angles were small in relation to the other one, and that a sequence of angular displacements was defined. This approach required the sole determinations of the planar coordinates of the three points delimiting the orthogonal rods. An experimental setup was designed to validate the method: the criterion angles were approximated with less than 2 degrees of error. Subsequently, the method was applied to a practical situation: the two-legged stop in ice hockey. The combination of this tridimensional method with instrumented strain gauge skates for the measurement of forces provides a new and powerful tool for performing kinetic analyses in tridimensional skating activities.     

Fragments: the implications for teachers,learners and media users/researchers of personal construal and fragmentary recollection of aural and visual messages

A theory is advanced which proposes that when experience is recalled, it is recalled in fragments. The fragments are then woven logether to make a story about the experience, which is what is often called construal, or making sense. There are manifold implications of the theory: in the design of instruction which explicitly employs the theory in the ways in which students are invited to work on materials in different media; for assessment which explicitly calls upon fragment processing skills; for research into the effective use of educational media.     

Our shrinking ozone layer

Depletion of the Earth’s ozone layer is one of the major environmental concerns for the new millennium having serious implications on human health, agriculture and climate. In the past decades, research by the international scientific community has been directed towards understanding the impact of human interference on the Earth’s atmosphere. The importance of ozone radiation absorption in the atmosphere and the general kinetics of the stratospheric ozone depletion mechanisms have motivated many theoretical and experimental studies on various chemical species. The distribution of ozone and other trace gases in the atmosphere is governed by the complex interaction of dynamical, chemical and radiative processes. This article concentrates on the basic concepts underlying the problems that may be faced by humankind due to reduction in the ozone layer in coming decades, and the ways in which the scientific community can contribute to predicting and remediating these effects through design of international treaties, regulations and amendments.