Impact of school outdoor environment upon pupils' physical activity and sun exposure across ages and seasons

Background and aims: Among children, the lack of physical activity (PA) is widespread in developed countries. Further, the majority of all skin cancers depend on an overexposure to solar ultraviolet radiation (UVR) in early life. The combination of sufficient PA and suberythemal UVR exposure (potentially sufficient for vitamin D production) dispersed over the day is vital to general wellbeing and bone health, especially in growing children and adolescents. However, long regulated school days entail less free mobility and outdoor stay, which may jeopardize the opportunities for cohesive intense physical activity (PA) and suberythemal UVR exposure. The impact of the school outdoor environment upon schoolchildren’s PA has been studied but not in combination with the exposure to UVR from the sun during the school day in children of different ages during one academic year containing different seasons. The overall aim for this thesis was to examine the crosssectional impact of outdoor environments at compulsory school level in different seasons upon PA and solar UVR exposure in Swedish pupils. Material and Methods: The impact of school outdoor environment upon pupils' physical activity and UVR exposure during free-mobility, scheduled time and physical education (PE) were studied in 196 pupils aged 7-15 years (grades 2, 5, and 8) at four schools in mid-southern Sweden during 5 consecutive days each in September, March and May. Actigraph GT3X+ Activity monitors were used for PA assessments and for separation of indoor from outdoor stay, supplementary to ocular observation. Predictors for PA during school stay, expressed as mean daily accelerometer counts and time in different PA intensities were measured per season, day, grade and gender. For individual assessment of erythemally effective UVR (joule per exposed m2 of the skin), a polysulphone film dosimeter badge was pinned to the top of the pupils’ right shoulders and worn during school-time during the entire week. Their individual UVR exposures were related to and expressed as fractions of total available ambient UVR in the schools’ outdoor environments which differed considering amount of shade, vegetation, and peripheral city-scape quantified as percentage of free sky view calculated by fish-eye photography. Questionnaires and diaries were applied to control for confounders. Results: Overall, free-living PA outdoors generated the highest mean accelerometer counts for moderate and vigorous physical activity (MVPA), and together with outdoor physical education contributed with 50% of total mean accelerometer counts though representing only 25% of the total school time. Season, age, gender and weather had an impact on both PA and UVR exposure, with less PA and UVR exposure. In March, in inclement weather both PA and UVR exposure dropped, especially among older pupils and girls. During all seasons both MVPA counts and UVR exposures were significantly higher among 2nd graders vs. 5th and 8th graders. In September and March play at sport fields had a positive impact on pupils’ PA and suberythemal sun exposure (potentially sufficient for vitamin D production). Among 2nd and 5th graders and in September this interaction between attributes of the physical environment and level of PA and UVR exposure was pronounced. In May overexposure to UVR did occur, though green settings with trees and shrubs and fixed play equipment close to the greenery protected from hazardous UV exposure and promoted high levels of MVPA. Conclusions: More time outdoors, at all seasons, would favorably increase school children´s chances of reaching recommended levels of PA. There is a potential for prolonged suberythemal outdoor stay for play in open areas during fall and early spring at Lat.56oN. Outdoor activities in such settings should therefore be encouraged. In late spring, long outdoor exposures of the youngest pupils warrant UVR-protective outdoor environment. Access to vegetation and/or shaded structures (e.g. trees, bushes, roofs) attractive for play should be provided for

Landau-Ginsberg Theory of Quark Confinement

We describe the SU(3) deconfinement transition using Landau-Ginsberg theory. Drawing on perturbation theory and symmetry principles, we construct the free energy as a function of temperature and the Polyakov loop. Once the two adjustable parameters of the model are fixed, the pressure p, energy epsilon and Polyakov loop expectation value P_F are calculable functions of temperature. An excellent fit to the continuum extrapolation of lattice thermodynamics data can be achieved. In an extended form of the model, the glueball potential is responsible for breaking scale invariance at low temperatures. Three parameters are required, but the glueball mass and the gluon condensate are calculable functions of temperature, along with p, epsilon and P_F.Comment: Lattice99(Finite Temperature and Density) <= added keywords only change in revised version, sorry; 3 pages, LaTeX with espcrc2.sty and epsf.tex. Talk presented at Lattice99, Pisa, 29 June - 3 July 1999, to appear in Nucl. Phys. B (Proc.Suppl.

Verifying the Kugo-Ojima Confinement Criterion in Landau Gauge Yang-Mills Theory

Expanding the Landau gauge gluon and ghost two-point functions in a power series we investigate their infrared behavior. The corresponding powers are constrained through the ghost Dyson-Schwinger equation by exploiting multiplicative renormalizability. Without recourse to any specific truncation we demonstrate that the infrared powers of the gluon and ghost propagators are uniquely related to each other. Constraints for these powers are derived, and the resulting infrared enhancement of the ghost propagator signals that the Kugo-Ojima confinement criterion is fulfilled in Landau gauge Yang-Mills theory.Comment: 4 pages, no figures; version to be published in Physical Review Letter

Energy-momentum tensor form factors of the nucleon in nuclear matter

The nucleon form factors of the energy-momentum tensor are studied in nuclear medium in the framework of the in-medium modified Skyrme model. We obtain a negative D-term, in agreement with results from other approaches, and find that medium effects make the value of d_1 more negative.Comment: 9 pages, 11 figures. Some typos were removed and one reference was adde

Compulsory School In- and Outdoors—Implications for School Children’s Physical Activity and Health during One Academic Year

Regulated school days entail less free-living physical activity (PA) and outdoor stay, which may jeopardize the opportunities for cohesive moderate-to-vigorous physical activity (MVPA) and, by extension, children’s health. The role of outdoor stay during school time for pupils’ free-living PA vs. physical education (PE) and indoor stay was studied during one academic year in 196 pupils aged 7–14 years at four schools in mid-southern Sweden during five consecutive days each in September, March, and May. Actigraph GT3X+ Activity monitors were used. Predictors for PA during school stay were expressed as mean daily accelerometer counts and were measured per season, day, grade, gender, weather, and time outdoors. Overall, free-living PA outdoors generated the highest mean accelerometer counts for moderate and vigorous PA. Outdoor PA and PE, representing 23.7% of the total school time contributed to 50.4% of total mean accelerometer counts, and were the greatest contributors to moderate and vigorous PA. Age and weather impacted PA, with less PA in inclement weather and among older pupils. More time outdoors, at all seasons, would favorably increase school children’s chances of reaching recommended levels of PA

Att studera förskolebarns fysiska aktivitet

Förskolebarns fysiska aktivitet har en viktig hälsopromotiv effekt mot flera av våra välfärdssjukdomar. Därför är det av yttersta vikt att förskolemiljön stimulerar förskolebarnen till en hälsosam fysisk aktivitet. I Kidscape projektet studerade vi förskolebarns fysiska aktivitet under vistelsen på förskolan. Syftet var att hitta faktorer i skolgårdens utemiljö som påverkar barnens aktivitetsmönster. Aktivitetsmönstret studerades med både subjektiva (CARS och kvalitativ observation) och objektiva metoder (pedometri och accelerometri). Resultatet visade att förskolebarnens fysiska aktivitet var högre i förskolor med en bra skolgårdsmiljö. Slutsats: förskole gårdens utformning kan främja en hälsosam fysisk aktivitet hos förskolebarn