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21.
22.
Jakob L. Vingren Ronald G. Budnar Jr. Amy L. McKenzie Anthony A. Duplanty Hui-Ying Luk Danielle E. Levitt 《Journal of sports sciences》2016,34(8):694-699
This study investigated the acute endocrine responses to a 164-km road cycling event in a hot environment. Thirty-four male experienced cyclists (49.1 ± 8.3 years, 86.8 ± 12.5 kg, 178.1 ± 5.1 cm) participating in a 164-km road cycling event were recruited. Blood samples were collected within 0.3–2.0 h before the start (PRE: ~0500–0700 h) and immediately following the ride (POST). Samples were analysed for testosterone, growth hormone (GH), cortisol and interleukin-6 (IL-6). The temperature and humidity during the event were 35.3 ± 4.9°C and 47.2 ± 14.0%, respectively. Based on the finishing time, results for the fastest (FAST, 305 ± 10 min) and the slowest (SLOW, 467 ± 31 min) quartiles were compared. At POST, testosterone concentration was significantly (P < 0.05) lower (PRE, 20.8 ± 8.6; POST, 18.2 ± 6.7 nmol · L?1), while GH (PRE, 0.3 ± 0.1; POST, 2.3 ± 0.3 µg · L?1), cortisol (PRE, 661 ± 165; POST, 1073 ± 260 nmol · L?1) and IL-6 (PRE, 4.0 ± 3.4; POST, 22.4 ± 15.2 pg · mL?1) concentrations were significantly higher than those at PRE. At POST, GH and cortisol were significantly higher for the FAST group than for the SLOW group (GH, 3.6 ± 2.0 and 1.0 ± 0.8 µg · L?1; cortisol, 1187 ± 209 and 867 ± 215 nmol · L?1). Participation in an ultra-endurance road cycling event in a hot environment induced significant acute changes in concentrations of circulating hormones, with a greater augmentation of GH and cortisol in those completing the ride fastest. 相似文献
23.
Jordan J. Smith Philip J. Morgan Ronald C. Plotnikoff David F. Stodden David R. Lubans 《Journal of sports sciences》2016,34(8):772-779
The purpose of this study was to examine the mediating effect of resistance training skill competency on percentage of body fat, muscular fitness and physical activity among a sample of adolescent boys participating in a school-based obesity prevention intervention. Participants were 361 adolescent boys taking part in the Active Teen Leaders Avoiding Screen-time (ATLAS) cluster randomised controlled trial: a school-based program targeting the health behaviours of economically disadvantaged adolescent males considered “at-risk” of obesity. Body fat percentage (bioelectrical impedance), muscular fitness (hand grip dynamometry and push-ups), physical activity (accelerometry) and resistance training skill competency were assessed at baseline and post-intervention (i.e., 8 months). Three separate multi-level mediation models were analysed to investigate the potential mediating effects of resistance training skill competency on each of the study outcomes using a product-of-coefficients test. Analyses followed the intention-to-treat principle. The intervention had a significant impact on the resistance training skill competency of the boys, and improvements in skill competency significantly mediated the effect of the intervention on percentage of body fat and the combined muscular fitness score. No significant mediated effects were found for physical activity. Improving resistance training skill competency may be an effective strategy for achieving improvements in body composition and muscular fitness in adolescent boys. 相似文献
24.
The steady-state electrical conductivity,as well as the dielectric propertiesbetween 2×10~(-4)Hz and 100 kHz,and at 1 GHz,are reported for urease compressed powdersamples of low hydration.The results show that the large,low frequency dielectricdispersion,known as α-dispersion,is due to the build-up of a space charge of protons atthe sample-electrode interfaces.A smaller dispersion,appearing at higher frequencies,isconcluded to be associated with hindered motions of the peptide residues in the molecularstructure of urease.The extent of these polypeptide backbone motions is shown to bestrongly depended on the extent of enzyme hydration.This work is contributed to the de-velopment of conductimetric biosensors. 相似文献
25.
The purpose of the study was to examine the relationship of classroom environment to attitudes toward science and achievement in science among tenth grade biology students. An attitude instrument was administered at three times during the school year to measure student attitudes toward science and the classroom environment. The classroom environment measures examined six areas: emotional climate of the science classroom, science curriculum, physical environment of the science classroom, science teacher, other students in the science classroom, and friends attitudes toward science. Student achievement in science was measured by teacher reported semester grades. The results of the study indicated: (1) student attitudes toward the classroom environment predicted between 56 to 61% of the variance in attitudes toward science, (2) student attitudes toward the classroom environment predicted between 5 to 14% of the variance in achievement in science, (3) student attitudes toward science and attitudes toward the classroom environment predicted between 8 and 18% of the variance in achievement in science. 相似文献
26.
Kim M. Tsai Ronald E. Dahl Michael R. Irwin Julienne E. Bower Heather McCreath Teresa E. Seeman David M. Almeida Andrew J. Fuligni 《Child development》2018,89(5):1577-1588
The current study examines the association between parental support and adolescent sleep under varying levels of family stress. Participants included 316 adolescents (Mage = 16.40 years, 43% male) and their parents (Mage = 45.67 years, 91% mothers) from diverse ethnic backgrounds. Both adolescents and parents completed questionnaires and adolescents wore wrist actigraphs and completed self‐reports on their sleep for 7 consecutive days. Results indicated that under contexts of family stress, more parental support was linked to longer sleep duration, less sleep variability, and less time spent awake during the night. Findings suggest that under contexts of family stress, cohesive family relationships may provide a sense of stability and security that is necessary for healthful sleep. 相似文献
27.
Ronald J. Raven 《科学教学研究杂志》1972,9(3):207-212
The purpose of this study was to determine if achievement on a series of problems was affected by differences among task values within a dimension. Values within inference pattern, goal object, and percept dimensions were studied. One hundred and sixty primary school children participated in the study. An analysis of the results of their achievement on the tasks indicate that task solution is affected by the dimension values used in this study. The results of the study suggest that a multidimensional scale of task dimension values should be constructed in order to assist the curriculum specialist in the construction and sequencing of concept tasks for specific grade levels. 相似文献
28.
This study assessed the perceptions of 146 gifted and 115 non-gifted high school biology students and investigated associations
between student perceptions and cognitive achievement. The What Is Happening In this Class? (WIHIC) was used to assess perceptions
of actual and preferred learning environments. Data indicated that all students preferred a more favourable environment than
the one that they were currently experiencing, but gifted students perceived their actual environment more positively than non-gifted students. Statistically significant associations between the actual learning
environment and achievement on a standardised biology test were found for the majority of scales. Teacher Support, Investigation
and Equity were all statistically significant independent predictors of student achievement, while Student Cohesiveness had
a negative association with achievement. Interviews revealed that students interpreted some WIHIC items differently from how
the developers had intended. 相似文献
29.
30.
Graduation patterns were examined for 905 deaf students (1990-1998) at the National Technical Institute for the Deaf. Students with higher reading and language skills had the best overall graduation percentage. Comparison of recipients of different degrees--bachelor of science (BS) versus fine arts (BFA); associate of applied science (AAS) versus occupational studies (AOS)--showed 92% of BS and 82% of AAS graduates reading at the 9th-grade level or above, versus 65% of BFA and 47% of AOS graduates. Interestingly, 80% of non-degree-earning students read at the 9th-12th grade levels; in absolute terms, they outnumbered graduates with similar reading skills in the AAS and BFA programs combined, and in the BS program. This indicates a need for improved counseling, placement, and retention strategies. Students performed similarly across degree categories, regardless of curriculum requirements and difficulty. Only non-degree-earning students had significantly lower grade averages. 相似文献