Effect of Caffeine Ingestion on Cardiorespiratory Endurance in Men and Women     

N. K. Butts  D. Crowell 《Research quarterly for exercise and sport》2013,84(4):301-305

Abstract

The effect of caffeine ingestion on submaximal endurance performance of 15 females and 13 males was investigated. After completing a [Vdot]O ₂ max test, each subject performed two submaximal cycling tests at approximately 75% of [Vdot]O ₂ max to exhaustion. For the caffeine (C) trials, 300 mg of caffeine was added to 250 ml of decaffeinated coffee and ingested one hour prior to the exercise. The decaffeinated (D) trial involved consuming 250 ml of decaffeinated coffee an hour prior to the test. The C and D trials were administered randomly using a standard double blind design. Physiological parameters were monitored each 9, 10, and 11 minute intervals throughout each trial and averaged. As expected the [Vdot]O ₂ (L · min ^?1 ), [Vdot]E and work outputs (kgm) were significantly (p < 0.001) higher for the males than the females. All other variables, time to exhaustion, [Vdot]O ₂ (ml · kg · min ^?1 ), R, HR, and rating of perceived exertion (RPE) were not significantly (p > 0.05) different between the sexes for either the C or D trials. Time to exhaustion was 14.4 and 3.1% longer for the C trials for the females and males, respectively, however these increases were not significant (p > 0.05). Furthermore, there were no significant differences (p > 0.05) for any of the measured variables during successive 10 minute work intervals between the C and D trials for either sex. These results do not support the general use of caffeine in moderate amounts as an ergogenic aid for either males or females, but from a practical point it appears that caffeine may have an ergogenic effect on specific individuals.  相似文献   

Cycling power output produced during flat and mountain stages in the Giro d'Italia: A case study     

Stefan Vogt  Yorck Olaf Schumacher  Andreas Blum  Kai Roecker  Hans-Hermann Dickhuth  Andreas Schmid 《Journal of sports sciences》2013,31(12):1299-1305

Abstract

Until recently, the physiological demands of cycling competitions were mostly reflected by the measurement of heart rate and the indirect estimation of exercise intensity. The purpose of this case study was to illustrate the varying power output of a professional cyclist during flat and mountain stages of a Grand Tour (Giro d'Italia). Nine stage recordings of a cyclist of the 2005 Giro d'Italia were monitored using a mobile power measurement device (SRM Trainingssystem, Julich, Germany), which recorded direct power output and heart rate. Stages were categorized into flat (n = 5) and mountain stages (n = 4). Data were processed electronically, and the overall mean power in flat and mountain stages and maximal mean power for various durations were calculated. Mean power output was 132 W ± 26 (2.0 W · kg^?1 ± 0.4) for the flat and 235 W ± 10 (3.5 W · kg^?1 ± 0.1) for the mountain stages. Mountain stages showed higher maximal mean power (367 W) for longer durations (1800 s) than flat stages (239 W). Flat stages are characterized by a large variability of power output with short bursts of high power and long periods with reduced intensity of exercise, whereas mountain stages mostly require submaximal, constant power output over longer periods.  相似文献   

Triathlon     

Tamika Heiden  Angus Burnett 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(1):35-49

The aim of this study was to determine the effect of prior cycling on EMG activity of selected lower leg muscles during running. Ten elite level triathletes underwent two testing sessions at race pace: a 40 km cycle followed by a 2 km run (CR) and a 10 km run followed by a 2 km run (RR). EMG data from selected lower limb muscles were collected at three sections of each run (0 km, 1 km and 2 km) for six strides using a portable data logger. Significant differences (p < 0.05) between condition were found for the level of activation (L_act) for biceps femoris (BF) during stance and vastus lateralis (VL) during flight and stance. Vastus medialis (VM) changed in L_act, during flight, between sections in the 2 km run. Furthermore, significant differences (p < 0.05) between condition were found for BF during stance and for rectus femoris (RF) and VM during flight. There was a significant difference (p < 0.05) in the duration of VL activation (D_act) across sections of the 2 km run. Findings from this investigation highlight changes in muscle function when changing from cycling to running and indicate a need to train specifically for the cycle to run transition. Such training may improve performance and reduce the risk of injury.  相似文献   

Development and field validation of an omni-domain power-duration model     

Michael J. Puchowicz  Jonathan Baker 《Journal of sports sciences》2020,38(7):801-813

ABSTRACT

Purpose: To validate and compare a novel model based on the critical power (CP) concept that describes the entire domain of maximal mean power (MMP) data from cyclists.

Methods: An omni-domain power-duration (OmPD) model was derived whereby the rate of W? expenditure is bound by maximum sprint power and the power at prolonged durations declines from CP log-linearly. The three-parameter CP (3CP) and exponential (Exp) models were likewise extended with the log-linear decay function (Om3CP and OmExp). Each model bounds W? using a different nonconstant function, W?eff (effective W?). Models were fit to MMP data from nine cyclists who also completed four time-trials (TTs).

Results: The OmPD and Om3CP residuals (4 ± 1%) were smaller than the OmExp residuals (6 ± 2%; P < 0.001). W?eff predicted by the OmPD model was stable between 120–1,800 s, whereas it varied for the Om3CP and OmExp models. TT prediction errors were not different between models (7 ± 5%, 8 ± 5%, 7 ± 6%; P = 0.914).

Conclusion: The OmPD offers similar or superior goodness-of-fit and better theoretical properties compared to the other models, such that it best extends the CP concept to short-sprint and prolonged-endurance performance.  相似文献   

Control,consent and complicity in the coaching of elite women’s cycling in Australia: a media analysis     

Chris Zehntner  Kerry R. McGannon  Jenny McMahon 《Sport, Education and Society》2019,24(5):520-532

The purpose of this study was to extend understanding of how athletes and coaches in a women’s cycling talent development and selection programme negotiate and normalise athlete abuse in the media. A thematic analysis of six online cycling magazine articles and their representations of the Australian women’s elite cycling development camp was analysed to explore athletic abuse and the (re)production of coaching practices using Bourdieusian theory. The findings revealed a link between the expression of coaching practice and the maltreatment of athletes. Analysis of these articles also revealed that athletes were complicit in the normalisation of coaching practices through the misrecognition of social power embedded in the coaching intervention. The representations by athletes within the articles contributed narratives related to the reproduction and proliferation of abusive coaching practices. This study extends understanding of how taken for granted and power laden aspects of coaching practices can be presented in the media and highlights the implications for coaches, athletes and the general public that consume online cycling media content.  相似文献   

场地自行车在直弯道之间的速度波动研究   总被引：6，自引：4，他引：2  

张百鸣  沈金康  朱柏强 《体育科研》2005,26(1):57-60

用5台德国产自行车数据收集分析系统(SRM自行车仪),收集、处理在南京、深圳、昆明等场地自行车训练和比赛的生物力学数据,按照不同场地,不同骑行速度计算人车系统在进出直弯道时平均速度和最大速度的变化。结果表明:速度波动与场地半径有显著性关系。当自行车从直道进入弯道时速度增加,而自行车从弯道进入直道时速度减小。250m场地上的速度波动比333.3m场地更大。速度波动与运动员骑行速度没有显著性关系。  相似文献   

辽宁省城市循环经济发展水平综合评价     

冯艳 《锦州师范学院学报(哲学社会科学版)》2006,28(3):91-93

我国的许多城市已经面临越来越严重的资源、环境和发展的困境,通过循环经济建设可以改变城市的发展模式,提高城市的可持续发展能力.对循环经济的发展状况进行评价是发展循环经济的一个必要步骤,在充分考虑经济增长、社会进步与资源的有效利用、环境保护之间相互制约关系的基础上,建立循环经济评价指标体系,并对辽宁省各主要城市循环经济发展水平进行排序.  相似文献   

“互联网+体育”国际体育信息采集的研究--以国际场地自行车项目为例     

朱建伟  朱天然 《冰雪运动》2016,(4):27-33

对国际体育信息的采集、归纳、整理、分析,对把握国际体育发展的趋势,与世界保持同步具有重要的意义。国际奥委会、各种世界体育协会（联盟）的官方网站,世界著名媒体的新闻网站,自媒体是国际体育信息收集的主要网络渠道。筛选网络信息的原则是,泛览精收原则,有效确认原则。网络信息收集的注意事项是,尽量注明信息源出处,尊重作者版权;内容以专业人士学习、参考为主。信息采集的内容以各国比赛成绩资料的收集,国际比赛图像信息资料的收集,国际体育赛事的专项新闻信息收集为主。通过信息了解国际自盟（ UCI）项目设置的竞赛规则,了解国际规则变化及对手情况,掌握自行车专项器材、研究方法、手段的改进与创新等。  相似文献   

Agreement of Power Measures between Garmin Vector and SRM Cycle Power Meters     

Andrew R. Novak  Benjamin J. Dascombe 《Measurement in physical education and exercise science》2016,20(3):167-172

This study aimed to determine if the Garmin Vector (Schaffhausen, Switzerland) power meter produced acceptable measures when compared with the Schoberer Rad Messetechnik (SRM; Julich, Germany) power meter across a range of high-intensity efforts. Twenty-one well-trained cyclists completed power profiles (seven maximal mean efforts between 5 and 600 s) using Vector and SRM power meters. Data were compared using assessments of heteroscedasticity, t tests, linear regression, and typical error of estimate (TEE). The data were heteroscedastic, whereby the Vector pedals increasingly overestimated values at higher power outputs; however, t tests did not identify any significant differences between power meters (p > .05). Using linear regression, Vector data were fit to an SRM equivalent (slope = .99; intercept = ?9.87) and TEE produced by this equation was 3.3% (3.0%–3.8%). While the data shows slight heteroscedasticity due to differing strain-gauge placement and resultant torque measurement variance, the Vector appears acceptable for measures of power output across various cycling efforts.  相似文献   

浅谈C语言的循环结构及循环优化     

张丽姝 《天津职业院校联合学报》2001,3(4):77-82

C语言是结构化的程序设计语言,适合于编写系统软件,同时也适合作为程序设计教学语言.提高程序的执行效率是编程者所追求的目标,对循环做较深入的优化可以大幅度地提高程序的效率.  相似文献