1,721,040 research outputs found
Quantum mechanical simulations in semiconductor materials science: the tight-binding molecular dynamics approach
No full textMonitoring the internal and external loads of young team handball players during competition
Full text linkThis study aimed to examine the internal- and external-training-load (ITL and ETL, respectively) during a match of young handball players. Field testing included heart-rate monitoring (memory belt, Suunto) as a marker of ITL and accelerometry (motion-biosensor, Actical Respironcis, Philips) as a marker of ETL. Time motion analysis data were obtained by recording the player's game activities and later analysed with the Matlab software package. T-test and Pearson-product-moment correlation coefficient were used to examine the differences and the relationship between variables collected in the study. The t-test analysis did not show significant differences between the total distance covered (2216.42-2135.42 m), steps conducted (1829.25-1829.83 steps), steps per minute (91.46-91.49 steps/min), energy expenditure (92.24-90.87 METS), time spent in higher intensity zones calculated by motion biosensor (13.08-12.75 minutes), training-load calculated by Edwards TRIMP method (91.54-88.56 scores) in the first and in the second half of the match. Physical activity variables show no significant correlations with the data assessed by heart rate monitors. Similar results in monitored training-load variables in the first and second halves are connected with the game intensity, which was consistent throughout the match. The lack of correlations between ITL and ETL variables indicates that accelerometry is not suitable for the assessment of metabolic training load in intermittent activities, such as handball. ITL measures used in this study are more suitable for controlling load during training and competition, while the ETL parameters used are more appropriate for better understanding players activity in periods in which the players do not train; other activities can influence players fatigue and training and competition performance
Structure and dynamics of nitrite sodalite. An ab initio study
No full textWe present a first-principles study of nitrite sodalite, a synthetic zeolite. The NO2- anions are hosted in octahedral cavities typical of such crystals, and each anion is surrounded by four Na cations in a tetrahedral geometry. We found that NO2- is in a rotational state inside the zeolite's cages. This rotational state explains the orientational disorder experimentally detected in nitrite sodalite
Analysis of the relationship between tobacco smoking and physical activity in adolescence: a gender specific study
Full text linkBackground and Objective: Although smoking and the physical activity level (PAL) are important determinants of health status in adolescence, there is a lack of information on the relationship between smoking and PAL in early adolescence. The objective of this study was to evaluate the gender-specific relationship between smoking and PAL in 14-to-16-year-old adolescents. Materials and Methods: The sample included 650 adolescents (337 girls, 14.7 ± 0.5 years at first testing wave) from Bosnia and Herzegovina. During the first testing wave, participants were tested using struc-tured questionnaires. Second testing was commenced after approximately 20 months (16.4 ± 0.6 years). The variables were age, gender, socioeconomic status, living environment, cigarette smoking (predictors), and PAL (criterion). Predictors were measured at the first wave, and criterion at the first-wave and second-wave. Results: For girls, smoking was negatively correlated to PAL at the first-wave (OR: 0.75, 95% CI: 0.55–0.95) and at the second-wave (OR: 0.73, 95% CI: 0.71–0.96). No significant association between smoking and PAL was found for boys. Results suggest that adolescent boys and girls do not follow the equal trajectories when it comes to relationships between smoking and PAL. Conclusions: In developing promotional public health actions related to a decrease of smoking and increase of PAL, a gender-specific approach is highly recommended. Further studies analyzing the cause–effect relationship between consumption of other types of psychoactive substances and PAL in this age group are warranted
Toward prevention of doping in youth sport: Cross-sectional analysis of correlates of doping tendency in swimming
Full text linkDoping is recognized as one of the most important problems in sports, but a limited number of studies have investigated doping problems in youth athletes. This study aimed to evaluate doping tendency (potential doping behavior (PDB)) and correlates of PDB in youth age swimmers. The participants were 241 competitive swimmers (131 females; 15.3 ± 1.1 years of age, all under 18 years old). Variables included predictors and PDB (criterion). Predictors consisted of sociodemographic factors (gender and age), sport-related variables (i.e., experience in swimming and sport achievement), variables explaining coaching strategy and training methodology, consumption of dietary supplements (DS), knowledge about doping, and knowledge about sports nutrition and DS (KSN). In addition to the descriptive statistics and differences between genders, a multinomial regression using PDB as the criterion (negative-, neutral-, or positive-PDB, with a negative-PDB as the reference value) was calculated to define associations between predictors and criterion. With only 71% of swimmers who declared negative-PDB results indicated an alarming figure. Boys with better KSN were more negatively oriented toward positive-PDB (OR: 0.77, 95%CI: 0.60–0.95). In girls, lower competitive achievement was evidenced as a risk factor for neutral-PDB (OR: 0.39, 95%CI: 0.24–0.63). Also, higher neutral-PDB (OR: 0.88, 95%CI: 0.81–0.96) and positivePDB (OR: 0.90, 95%CI: 0.83–0.99) were identified in girls who began with intensive training in younger age. Because of the alarming figures of PDB, there is an evident need for the development of systematic antidoping educational programs in youth swimming. In doing so, focus should be placed on girls who began intensive training at an earlier age and those who did not achieve high competitive results
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