A calibration protocol for population-specific accelerometer cut-points in children

Purpose

To test a field-based protocol using intermittent activities representative of children's physical activity behaviours, to generate behaviourally valid, population-specific accelerometer cut-points for sedentary behaviour, moderate, and vigorous physical activity.
Methods

Twenty-eight children (46% boys) aged 10–11 years wore a hip-mounted uniaxial GT1M ActiGraph and engaged in 6 activities representative of children's play. A validated direct observation protocol was used as the criterion measure of physical activity. Receiver Operating Characteristics (ROC) curve analyses were conducted with four semi-structured activities to determine the accelerometer cut-points. To examine classification differences, cut-points were cross-validated with free-play and DVD viewing activities.
Results

Cut-points of ≤372, >2160 and >4806 counts•min−1 representing sedentary, moderate and vigorous intensity thresholds, respectively, provided the optimal balance between the related needs for sensitivity (accurately detecting activity) and specificity (limiting misclassification of the activity). Cross-validation data demonstrated that these values yielded the best overall kappa scores (0.97; 0.71; 0.62), and a high classification agreement (98.6%; 89.0%; 87.2%), respectively. Specificity values of 96–97% showed that the developed cut-points accurately detected physical activity, and sensitivity values (89–99%) indicated that minutes of activity were seldom incorrectly classified as inactivity.
Conclusion

The development of an inexpensive and replicable field-based protocol to generate behaviourally valid and population-specific accelerometer cut-points may improve the classification of physical activity levels in children, which could enhance subsequent intervention and observational studies.

Comparing different accelerometer cut-points for sedentary time in children

Actigraph accelerometers are hypothesized to be valid measurements for assessing children's sedentary time. However, there is considerable variation in accelerometer cut-points used. Therefore, we compared the most common accelerometer sedentary cut-points of children performing sedentary behaviors. Actigraph Actitrainer uniaxial accelerometers were used to measure children's activity intensity (29 children, 5-11 years old) during different activities, namely playing computer games, nonelectronic sedentary games, watching television and playing outdoors. A structured protocol was the criterion for assessing the validity of four common cut-points (100, 300, 800, 1100 counts/minute). The median counts during all sedentary behaviors were below the lowest comparison cut-point of 100 cpm. The 75th percentile values for the sedentary behaviors were always below the cut-point of 300 cpm. Our results suggest that the cut-point of <100 cpm is the most appropriate.

A health restructure, but the treatment misses some key points

The reforms need more focus on indigenous care, funding transparency and preventative medicine, writes Jim Hyde.

Extracting 3D mesh skeletons using antipodal points locations

Finding the skeleton of a 3D mesh is an essential task for many applications such as mesh animation, tracking, and 3D registeration. In recent years, new technologies in computer vision such as Microsoft Kinect have proven that a mesh skeleton can be useful such as in the case of human machine interactions. To calculate the 3D mesh skeleton, the mesh properties such as topology and its components relations are utilized. In this paper, we propose the usage of a novel algorithm that can efficiently calculate a vertex antipodal point. A vertex antipodal point is the diametrically opposite point that belongs to the same mesh. The set of centers of the connecting lines between each vertex and its antipodal point represents the 3D mesh desired skeleton. Post processing is completed for smoothing and fitting centers into optimized skeleton parts. The algorithm is tested on different classes of 3D objects and produced efficient results that are comparable with the literature. The algorithm has the advantages of producing high quality skeletons as it preserves details. This is suitable for applications where the mesh skeleton mapping is required to be kept as much as possible.

Predictive validity and classification accuracy of ActiGraph energy expenditure equations and cut-points in young children

Objectives
Evaluate the predictive validity of ActiGraph energy expenditure equations and the classification accuracy of physical activity intensity cut-points in preschoolers.

Methods
Forty children aged 4–6 years (5.3±1.0 years) completed a ~150-min room calorimeter protocol involving age-appropriate sedentary, light and moderate-to vigorous-intensity physical activities. Children wore an ActiGraph GT3X on the right mid-axillary line of the hip. Energy expenditure measured by room calorimetry and physical activity intensity classified using direct observation were the criterion methods. Energy expenditure was predicted using Pate and Puyau equations. Physical activity intensity was classified using Evenson, Sirard, Van Cauwenberghe, Pate, Puyau, and Reilly, ActiGraph cut-points.

Results
The Pate equation significantly overestimated VO2 during sedentary behaviors, light physical activities and total VO2 (P<0.001). No difference was found between measured and predicted VO2 during moderate-to vigorous-intensity physical activities (P = 0.072). The Puyau equation significantly underestimated activity energy expenditure during moderate-to vigorous-intensity physical activities, light-intensity physical activities and total activity energy expenditure (P<0.0125). However, no overestimation of activity energy expenditure during sedentary behavior was found. The Evenson cut-point demonstrated significantly higher accuracy for classifying sedentary behaviors and light-intensity physical activities than others. Classification accuracy for moderate-to vigorous-intensity physical activities was significantly higher for Pate than others.

Conclusion
Available ActiGraph equations do not provide accurate estimates of energy expenditure across physical activity intensities in preschoolers. Cut-points of ≤25counts⋅15 s−1 and ≥420 counts⋅15 s−1 for classifying sedentary behaviors and moderate-to vigorous-intensity physical activities, respectively, are recommended.

Material writing: Towards hybrid-making

Writing operates in an expanding field of intersections between symbol, inflection and further meaning. The materiality of writing, its embodied action, situated context and myriad substantive expressions, requires an interdisciplinary approach best advanced by collaborative teams and fuelled by collective concerns. At a recent design conference, Doha 2013: Hybrid Making, our team of creative arts researchers (Jondi Keane, Patrick West and Valerie Jeremijenko) conducted a workshop based on the idea of reverse engineering the notion of a souvenir, by starting with the sensation rather than the iconic image. The approaches explored by the group focused on the ways in which a sensation, emotion and/or idea attach to an object and how an object offers itself as an attractor for memory and indicate that when experience, sensation and place are emphasized, the materiality of writing comes to the fore. We assert that material writing allows or even requires a fluid movement between conceptual and perceptual modes of creative practice. In this paper we will unpack different methods of material writing: the materiality of the act of writing with substances, site-specific/site-conditioned writing and 3D printing. Through the particularity of each mode of material writing our discussions will examine the points of attachment that we, as symbolizing creatures, produce in order to orient and reconstruct a world on the fly. Material writing constantly brings us back to earth, anchoring us to the expanded processes integral to hybrid-making.

Shifting between third and first person points of view in EFL narratives

This article reports on the difference between points of view in narrating a short story. The EFL learners taking part in the control group were required to recount the events from the third person perspective and the subjects in the experimental group from the first person perspective. The methodological frame of the study was based on Koven’s (2002) ‘content analysis’ of codification of various speaker role inhabitances, published in the Journal of Pragmatics. The results demonstrate that the first person narrators’ recall performance and the length of their stories are closer to the original version of the story than those of the other group, which indicates a specific ‘orientation’ towards the sequence of events. This was seen in the patterning of clauses as well as in authorial and interlocutory double voicing speech in the first person narrators, which may be justified by the enhancement of two components essential to literary engagement: namely, ‘aesthetic reading’ and ‘personal response’ as parts of ‘critical focalization’.

Points in mental space: an interdisciplinary study of imagery in movement creation

As part of a programme of research that is developing tools to enhance choreographic practice, an interdisciplinary team of cognitive scientists, neuroscientists and dance professionals collaborated on two studies examining the mental representations used to support movement creation. We studied choreographer Wayne McGregor's approach to movement creation through tasking, in which he asks dancers to create movement in response to task instructions that require a great deal of mental imagery and decision making

Personal resilience in times of crisis : the implications of SWB homeostasis and set-points

Our companion paper (Cummins et al. in J Happiness Stud, 2013) describes the statistical process used to demonstrate set-points and set-point-ranges for subjective wellbeing. The implications of set-points and homeostasis are now considered in the context of resilience. This discussion leads with a brief overview of resilience definitions and is followed by a description of subjective wellbeing (SWB) homeostasis. This addresses, in particular, the issue of SWB malleability under homeostatic control. The link between resources and resilience is then considered, in terms of predictions made by homeostasis theory. Finally, discussion focuses on the implications of such understanding for future directions in SWB research. It is concluded that an understanding of set-points and homeostasis allows new insights into the resilience construct.

A demonstration of set-points for subjective wellbeing

This paper presents evidence for the existence of ‘set-points’ for subjective wellbeing. Our results derive from a 10-year longitudinal study in which subjective wellbeing has been measured using a single question of general life satisfaction. The process of data analysis is driven by logic based on the theory of subjective wellbeing homeostasis. This analysis involves the iterative elimination of raw data, from 7,356 individual respondents, based on confidence limits. All results are projected onto a 0–100 point scale. We demonstrate evidence for the existence of set-points lying between 71 and 90 points, with an average set-point-range of 18–20 points for each person. The implications and limitations of these findings are discussed.