Sport selection in under-17 male roller hockey     

Manuel J. Coelho-E-Silva  Vasco Vaz  Filipe Simões  Humberto M. Carvalho  João Valente-Dos-Santos  António J. Figueiredo 《Journal of sports sciences》2013,31(16):1793-1802

Abstract

Characteristics of 32 international and 41 local under-17 (U-17) (14.5–16.5 years) roller hockey players were considered in the context of discrimination by competitive level using training history, anthropometry, skeletal maturation, and several laboratory and field performance tests. More international (42%) than local (22%) players were advanced in maturity status. International players had slightly less hockey experience (years), but had more practice sessions and match time (minutes) during the season. Local players were shorter and attained better performance in the 25-m dash, while international players performed better in sit-ups, ball throw and 20-m shuttle run. The fatigue index derived from the Wingate anaerobic test was higher among local players, while peak torques of knee extension and flexion were greater in international players. Stepwise discriminant function correctly classified 85% of players by competitive level based on grip strength, ratio of eccentric and concentric knee extension, number of training sessions, playing time and fatigue index. The results suggested an interaction among strength, anaerobic fitness and training plus game time as factors in discriminating international from local level players and by inference in the selection and development of youth roller hockey players.  相似文献   

Pre-exercise antioxidant enzyme activities determine the antioxidant enzyme erythrocyte response to exercise     

P Tauler  A Aguiló  P Guix  F Jiménez  G Villa  JA Tur 《Journal of sports sciences》2013,31(1):5-13

Free radical production increases during exercise and oxidative damage occurs in several tissues. We examined the effects of three different exercise tests on the pattern of change of erythrocyte enzyme antioxidant activities. The tests were a short maximal exercise test, a submaximal prolonged exercise test and a cycling stage during competition. The participants were amateur and professional cyclists with different training statuses and different basal erythrocyte antioxidant enzyme activities. The maximal test produced no changes in the erythrocyte antioxidant enzyme activities of amateur sportsmen. The submaximal test, performed at 80% of maximal oxygen uptake, decreased erythrocyte catalase (12%), glutathione peroxidase determined with H₂O₂ (14%) and glutathione reductase (16%); superoxide dismutase activity increased by about 25%. The cycling stage performed by professional cyclists increased erythrocyte catalase (29%) and glutathione reductase (10%) activities. The in vivo changes in glutathione reductase activity were confirmed by in vitro measurements: hydrogen peroxide decreased and the presence of catalase increased the activity of this enzyme. In conclusion, we suggest that the different erythrocyte antioxidant enzyme responses to diverse exercise tests can be explained by the effects of hydrogen peroxide and the superoxide anion on the antioxidant enzyme activities in erythrocytes.  相似文献   

A comparison of methods to determine maximal accumulated oxygen deficit in running     

Laurent Bosquet  Antoine Duchene  Paul Raoul Delhors  Gregory Dupont  Helen Carter 《Journal of sports sciences》2013,31(6):663-670

Abstract

The aim of this study was to compare maximal accumulated oxygen deficit (hereafter O₂ deficit) estimated from the methods of Whipp et al. (1986 Whipp, B. J., Ward, S. A. and Wasserman, K. 1986. Respiratory markers of the anaerobic threshold. Advances in Cardiology, 35: 47–64. [Crossref], [PubMed] , [Google Scholar]), Medbo et al. (1988 Medbo, J. I., Mohn, A. C., Tabata, I., Bahr, R., Vaage, O. and Sejersted, O. M. 1988. Anaerobic capacity determined by maximal accumulated O₂ deficit. Journal of Applied Physiology, 64: 50–60. [PubMed], [Web of Science ®] , [Google Scholar]), and Hill et al. (1998 Hill, D. W., Ferguson, C. S. and Ehler, K. L. 1998. An alternative method to determine maximal accumulated O₂ deficit in runners. European Journal of Applied Physiology, 79: 114–117. [Crossref], [Web of Science ®] , [Google Scholar]) to determine whether they agree sufficiently to be used interchangeably. Nineteen moderately to highly trained endurance runners first performed an incremental test to exhaustion for the determination of maximal oxygen uptake ([Vdot]O_2max) and peak treadmill speed, followed by six randomly ordered constant-speed tests at 95, 100, 105, 110, 110, and 120% of peak treadmill speed. All tests were separated by at least 72 h and were performed within 4 weeks. The method of Whipp produced an O₂ deficit estimate that was lower than that derived from the method of Hill or Medbo (bias ± 95% limits of agreement: ?29.6 ± 36.6 and ?26.1 ± 32.8 ml · kg^?1, respectively; P < 0.001). The O₂ deficit did not differ between the methods of Hill and Medbo (bias ± 95% limits of agreement: 3.5 ± 41.6 ml · kg^?1; n.s.). However, poor correlations (0.21 < r < 0.33; n.s.) together with wide limits of agreement between O₂ deficit estimates (70 – 80% of the mean response) clearly question using these methods interchangeably.  相似文献   

Maximum oxygen uptake and body composition of healthy Hong Kong Chinese adult men and women aged 20 – 64 years     

Samuel Yeung Shan Wong  Frank Wan Kin Chan  Chi Kei Lee  Martin Li  Fai Yeung  Christopher Chor Ming Lum 《Journal of sports sciences》2013,31(3):295-302

Abstract

The aims of the present study were to assess the maximal oxygen uptake and body composition of adult Chinese men and women, and to determine how these variables relate to age. The cross-sectional sample consisted of 196 men and 221 women aged 20 – 64 years. Maximal oxygen uptake ([Vdot]O_2max) was determined by indirect calorimetry during a maximal exercise test on an electrically braked cycle ergometer. The correlations between [Vdot]O_2max and fat mass were ?0.52 in men and ?0.58 in women. Linear regression defined the cross-sectional age-related decline in [Vdot]O_2max as 0.35 ml · kg^?1 · min^?1 · year^?1 in men and 0.30 ml · kg^?1 · min^?1 · year^?1 in women. Multiple regression analysis showed that more than 50% of this cross-sectional decline in [Vdot]O_2max was due to fat mass, lean mass, and age. Adding fat mass and lean mass to the multiple regression models reduced the age regression mass from 0.35 to 0.24 ml · kg^?1 · min^?1 · year^?1 in men and from 0.30 to 0.15 ml · kg^?1 · min^?1 · year^?1 in women. We conclude that age, fat mass, and lean mass are independent determinants of maximal oxygen uptake in Chinese adults.  相似文献   

Soccer and Zumba as health-promoting activities among female hospital employees: a 40-weeks cluster randomised intervention study     

Svein Barene  Peter Krustrup  Ole Lars Brekke  Andreas Holtermann 《Journal of sports sciences》2013,31(16):1539-1549

Abstract

The aim of this study was to evaluate the physiological effects of soccer and Zumba among female hospital employees during a 40-week intervention period. Hospital employees (n = 118) were cluster-randomised to either a soccer group (n = 41), a Zumba group (n = 38) or a control group (n = 39). Both training groups were encouraged to perform 1-h training sessions twice a week outside working hours throughout the 40 weeks. Maximal oxygen uptake (VO₂ max), blood pressure and body composition were measured and blood samples collected before and after the intervention period. Using intention-to-treat analyses, the Zumba group improved VO₂ max compared to the control group (2.2 mL · kg^?1 · min^?1, 95% CI, 0.9, 3.5, P = 0.001), with no significant increase in the soccer group (1.1 mL · kg^?1 · min^?1, 95% CI, ?0.2, 2.4, P = 0.08). Both intervention groups reduced total body fat mass and fat percentage compared to the control group (P < 0.01). In the soccer group, but not the Zumba group, a significant difference in lower limb bone mineral density and bone mineral content was observed in comparison to the control group (P < 0.01). Furthermore, the soccer group, but not the Zumba group, had increased plasma osteocalcin (6.6 µg · L^?1, 95% CI, 2.2, 11.0, P < 0.01) and decreased plasma leptin (?6.6 µg · L^?1, 95% CI, ?12.5, ?0.7, P < 0.05) compared to the control group. The present study suggests that workplace-initiated soccer and Zumba training comprising 1–2 sessions per week outside working hours may promote physiological health among female hospital employees.  相似文献   

Children-Adult Comparisons of VO2 and HR Kinetics during Submaximum Exercise     

Stanley P. Sady  Victor L. Katch  John F. Villanacci  Thomas B. Gilliam 《Research quarterly for exercise and sport》2013,84(1):55-59

Abstract

Oxygen uptake (VO₂) and heart rate (HR) kinetics for submaximum exercise were compared in prepubescent boys (mean age ± SD = 10.2 ± 1.28 years, N = 21) and adult men (30.0 ± 5.64 years, N = 21). Standard open circuit spirometric techniques were used to determine _VO2 and a bipolar ECG was used to measure HR. The kinetics of VO₂ and HR were determined for each subject using graphic procedures. Subjects performed submaximum exercise on the bicycle ergometer at an intensity of 42 ± 1.3% (mean ± SE) of VO₂ max for the children and 39 ± 0.7% of VO₂ max for the adults (p = .07). There were no group differences in VO₂ t1/2 (children t1/2 = 18.5 ± 0.75 secs and adults t1/2 = 17.4 ± 0.39 secs, p = .18) and HR t1/2 (children t1/2 = 11.4 ± 1.86 secs and adults t1/2 = 13.6 ± 1.66 secs, p = .38). These data suggest that children and adults do not differ in cardiorespiratory adjustments during low intensity exercise. This is in contrast to suggestions of other investigators that children have a faster cardiovascular adjustment to exercise.  相似文献   

Cardiorespiratory Responses to Downhill Versus Uphill Running in Endurance Athletes     

Marcel Lemire  Evelyne Lonsdorfer-Wolf  Marie-Eve Isner-Horobeti  Blah Y. L. Kouassi  Bernard Geny  Fabrice Favret 《Research quarterly for exercise and sport》2013,84(4):511-517

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Submaximal Treadmill Exercise Test to Predict VO2max in Fit Adults     

Pat R. Vehrs  James D. George  Gilbert W. Fellingham  Sharon A. Plowman  Kymberli Dustman-Allen 《Measurement in physical education and exercise science》2013,17(2):61-72

This study was designed to develop a single-stage submaximal treadmill jogging (TMJ) test to predict VO₂max in fit adults. Participants (N?=?400; men?=?250 and women?=?150), ages 18 to 40 years, successfully completed a maximal graded exercise test (GXT) at 1 of 3 laboratories to determine VO₂max. The TMJ test was completed during the first 2 stages of the GXT. Following 3 min of walking (Stage 1), participants achieved a steady-state heart rate (HR) while exercising at a comfortable self-selected submaximal jogging speed at level grade (Stage 2). Gender, age, body mass, steady-state HR, and jogging speed (mph) were included as independent variables in the following multiple linear regression model to predict VO₂max (R?=?0.91, standard error of estimate [SEE]?=?2.52 mL?·?kg^?1?·?min^?1): VO₂max (mL?·?kg^?1?·?min^?1)?=?58.687?+?(7.520 × Gender; 0?=?woman and 1?=?man)?+?(4.334 × mph) ? (0.211 × kg) ? (0.148 × HR) ? (0.107 × Age). Based on the predicted residual sum of squares (PRESS) statistics (R_PRESS?=?0.91, SEE _PRESS?=?2.54 mL?·?kg^?1?·?min^?1) and small total error (TE; 2.50 mL?·?kg^?1?·?min^?1; 5.3% of VO₂max) and constant error (CE; ?0.008 mL?·?kg^?1?·?min^?1) terms, this new prediction equation displays minimal shrinkage. It should also demonstrate similar accuracy when it is applied to other samples that include participants of comparable age, body mass, and aerobic fitness level. This simple TMJ test and its corresponding regression model provides a relatively safe, convenient, and accurate way to predict VO₂max in fit adults, ages 18 to 40 years.  相似文献   

测定空气中氧气含量的实验改进     

刘建华 《科教文汇》2012,(18):130-130,155

在测定空气中氧气含量的实验中,在由两个注射器组成的密闭系统中留有25mL空气,给装有细铜丝的玻璃管加热,同时缓慢推动两个注射器活塞,至玻璃管内的铜丝在较长时间内无进一步变化时停止加热,生成黑色固体氧化铜,待冷却至室温,将气体全部推至一个注射器内,观察密闭系统内空气体积变化。  相似文献   

MATLAB在锅炉效率中的应用     

吉世涛  邓华 《中国科技信息》2012,(9):146

常规的锅炉效率计算方法在日常的效率计算中不太方便,我们使用MATLAB这个功能强大的拟合工具进行效率计算,十分方便。另外,通过对数据的拟合,找到最佳排烟氧量,对锅炉燃烧进行优化。  相似文献