Roller ski rolling resistance and its effects on elite athletes’ performance     

Mats Ainegren  Peter Carlsson  Mats Tinnsten 《Sports Engineering》2009,11(3):143-157

Modern ski-treadmills allow cross-country skiers, biathletes and ski-orienteers to test their physical fitness in a laboratory environment whilst performing classical and freestyle (skating) techniques on roller skis. For elite athletes, the differences in performance between test occasions are quite small, thus emphasising the importance of knowing the roller skis’ rolling resistance in order to allow the correct comparison between the results of different test occasions. In this study, the roller skis’ rolling resistance was measured on the ski-treadmill’s surface using a roller ski rolling resistance measurement system specially produced for this purpose. The study investigated the influence of significant changes in rolling resistance on physiological variables. The results showed that during submaximal exercise, power, oxygen uptake, heart rate and blood lactate were significantly changed by different rolling resistances, while there were no significant or only small changes to cycle rate, cycle length and ratings of perceived exertion. Incremental maximal tests showed that time to exhaustion was significantly changed by different rolling resistances and this occurred without significant changes in maximal power, maximal oxygen uptake, maximal heart rate and blood lactate, and that the influence on ratings of perceived exertion were insignificant or small.  相似文献   

蹴球运动负荷及其锻炼价值的探讨     

吴学勇 《福建体育科技》2009,28(4):24-25

运用统计分析法、归纳推理法,对蹴球运动的运动负荷进行统计分析以及对锻炼价值进行探讨。研究发现：蹴球运动的运动负荷较小,适宜于我种人群,尤其是社区群众的娱乐健身活动,其锻炼价值主要体现在可以培养运动情趣、活跃思维,对开展居民休闲娱乐活动有积极的作用。  相似文献   

论李贽的《水浒传》评点     

张同胜 《济宁师范专科学校学报》2009,30(4):16-19

通过把明容与堂刻本《李卓吾先生批评忠义水浒传》中的点评与《李贽文集》尤其是《焚书》、《续焚书》、《藏书》、《续藏书》等进行思想内容和行文风格等方面的比较,认为容与堂刻本《水浒传》中的点评不是叶昼托名李赞所为,而是李贽自己的评点。他的《焚书》、《藏书》等著述与对《水浒传》的评点都有共同点,即都着眼于朝廷国家的理治,“与圣教有益无害”。“忠义”思想是李贽评点《水浒传》的思想维度。“童心”说是李贽对《水浒传》进行艺术性评点的指导思想。其中,“真”、“趣”是李贽评点《水浒传》两个重要的艺术维度。  相似文献   

高等师范学院女生篮球课内心演练的教法研究     

孙桂芳 《四川体育科学》2000,(2):35-38

内心演练教学法,用于高等师范女生篮球运球上篮技术教学之中,是一种新的尝试。内心演练教学法要求学生在练习篮球运动技术动作之前,在头脑中反复重现所学技术动作的形象,在脑中形象化、动作结构完整化和系统化,从而使技能达到熟练程度,形成技巧。  相似文献   

金葡液生产过程有关问题的探讨   总被引：1，自引：0，他引：1  

鲍行豪  方玮  王毅  陈玫 《科技通报》1999,15(1):55-60

金葡液生产前对生产用菌种进行复壮,有利于保护菌种的原有特性,使用酶解猪心汤作生产培养基,不仅可控制药液中的热原质,而且能使金葡菌生长繁殖更加良好,代谢产物增高。生产培养过程使用种子摇瓶,加在种子接种量,生产大瓶培养基的预温及培养过程中几次摇瓶,既可使培养基中过头成分被充分利用,代谢产物增多,又可缩短生产周期,稳定生产工艺,以β－丙内酯作原液或稀释灌封时的防腐剂,既可防止药液污染,又可减轻药物使用时  相似文献   

父权下的统治工具——康拉德《黑暗的心》中的记忆     

陈宇 《乐山师范学院学报》2013,(7):44-48

追溯到《圣经·出埃及记》中上帝出于对以色列人的承诺而不断对他们的记忆的强化,康拉德的《黑暗的心》中的记忆可视为父权社会的统治工具。马洛在旅途中邂逅之人的记忆为他的故事提供了重要的线索。此外,小说中的记忆有着强烈的排他性,这意味着马洛的故事是一个近乎只有男人的故事,并且有意流露出对女人的轻蔑和偏见。更为重要的是,小说中的记忆促成了故事的单向叙述,揭示了对女性的偏颇的评价,并且强调了殖民时期父权社会下的霸权统治。  相似文献   

谈康拉德《黑暗的心》中人物的狂欢化功能     

李晶然 《河北北方学院学报(社会科学版)》2012,(2):33-36

从狂欢化理论入手,分析了康拉德在《黑暗的心》中塑造的诸多具有狂欢化特征的人物,在此基础上进一步论述这些人物在主题方面体现出的平等自由和交替变更的精神,在形式两方面通过语言的运用和场景的设置达到讽刺性模拟和时空并置的效果。  相似文献   

Accuracy of an infrared LED device to measure heart rate and energy expenditure during rest and exercise     

C. Matthew Lee  Mark Gorelick  Albert Mendoza 《Journal of sports sciences》2013,31(15):1645-1653

Abstract

The purpose of this study was to examine the accuracy of the ePulse Personal Fitness Assistant, a forearm-worn device that provides measures of heart rate and estimates energy expenditure. Forty-six participants engaged in 4-minute periods of standing, 2.0 mph walking, 3.5 mph walking, 4.5 mph jogging, and 6.0 mph running. Heart rate and energy expenditure were simultaneously recorded at 60-second intervals using the ePulse, an electrocardiogram (EKG), and indirect calorimetry. The heart rates obtained from the ePulse were highly correlated (intraclass correlation coefficients [ICCs] ≥0.85) with those from the EKG during all conditions. The typical errors progressively increased with increasing exercise intensity but were <5 bpm only during rest and 2.0 mph. Energy expenditure from the ePulse was poorly correlated with indirect calorimetry (ICCs: 0.01–0.36) and the typical errors for energy expenditure ranged from 0.69–2.97 kcal · min^?1, progressively increasing with exercise intensity. These data suggest that the ePulse Personal Fitness Assistant is a valid device for monitoring heart rate at rest and low-intensity exercise, but becomes less accurate as exercise intensity increases. However, it does not appear to be a valid device to estimate energy expenditure during exercise.  相似文献   

Autonomic nervous system modulation during an archery competition in novice and experienced adolescent archers     

Andres E. Carrillo  Vasilios X. Christodoulou  Yiannis Koutedakis 《Journal of sports sciences》2013,31(9):913-917

Abstract

We assessed autonomic nervous system modulation through changes in heart rate variability during an archery competition as well as archery performance by comparing novice and experienced adolescent archers. Seven novice (age 14.0 ± 8.5 years, body mass index 22.9 ± 4.3 kg · m^?2, training experience 0.4 ± 0.3 years) and ten experienced archers (age 16.5 ± 10.3 years, body mass index 22.4 ± 3.1 kg · m^?2, training experience 4.1 ± 0.9 years) volunteered. Using beat-by-beat heart rate monitoring, heart rate variability was measured for 20 s before each arrow shot during two rounds of competition. We found that, compared with novices, experienced adolescent archers: (i) take more time per shot; (ii) have a higher low frequency band, square root of the mean of squared differences between successive R-R intervals (i.e. the time elapsing between two consecutive R waves in the electrocardiogram), and percentage of successive normal-to-normal intervals greater than 50 ms; and (iii) demonstrate an increase in parasympathetic nervous system activity compared with pre-competition values. We propose that these characteristics of experienced archers are appropriate for optimal performance during competition.  相似文献   

Exercise intensity and metabolic response in singles tennis     

Michael A. Christmass  Susan E. Richmond  Nigel T. Cable  Peter G. Arthur  Peter E. Hartmann 《Journal of sports sciences》2013,31(8):739-747

The aim of this study was to determine exercise intensity and metabolic response during singles tennis play. Techniques for assessment of exercise intensity were studied on-court and in the laboratory. The on-court study required eight State-level tennis players to complete a competitive singles tennis match. During the laboratory study, a separate group of seven male subjects performed an intermittent and a continuous treadmill run. During tennis play, heart rate (HR) and relative exercise intensity (72 ± 1.9% V O 2m ax ; estimated from measurement of heart rate) remained constant (83.4 ± 0.9% HR m ax ; mean s x ) after the second change of end. The peak value for estimated play intensity (1.25 ± 0.11 steps . s -1 ; from video analysis) occurred after the fourth change of end (P < 0.005). Plasma lactate concentration, measured at rest and at the change of ends, increased 175% from 2.13 ± 0.32 mmol . l -1 at rest to a peak 5.86 ± 1.33 mmol . l -1 after the sixth change of end (P < 0.001). A linear regression model, which included significant terms for %HR m ax (P < 0.001) and subject (P < 0.001), as well as a %HR max subject interaction (P < 0.05), accounted for 82% of the variation in plasma lactate concentration. During intermittent laboratory treadmill running, % V O 2peak estimated from heart rate was 17% higher than the value derived from the measured V O 2 (79.7 ± 2.2% and 69.0 ± 2.5% V O 2peak respectively; P < 0.001). The % V O 2peak was estimated with reasonable accuracy during continuous treadmill running (5% error). We conclude that changes in exercise intensity based on measurements of heart rate and a time-motion analysis of court movement patterns explain the variation in lactate concentration observed during singles tennis, and that measuring heart rate during play, in association with preliminary fitness tests to estimate V O 2 , will overestimate the aerobic response. (P < 0.001), estimated play intensity  相似文献