The influence of tyre characteristics on measures of rolling performance during cross-country mountain biking

This investigation sets out to assess the effect of five different models of mountain bike tyre on rolling performance over hard-pack mud. Independent characteristics included total weight, volume, tread surface area and tread depth. One male cyclist performed multiple (30) trials of a deceleration field test to assess reliability. Further tests performed on a separate occasion included multiple (15) trials of the deceleration test and six fixed power output hill climb tests for each tyre. The deceleration test proved to be reliable as a means of assessing rolling performance via differences in initial and final speed (coefficient of variation (CV) = 4.52%). Overall differences between tyre performance for both deceleration test (P = 0.014) and hill climb (P = 0.032) were found, enabling significant (P < 0.0001 and P = 0.049) models to be generated, allowing tyre performance prediction based on tyre characteristics. The ideal tyre for rolling and climbing performance on hard-pack surfaces would be to decrease tyre weight by way of reductions in tread surface area and tread depth while keeping volume high.     

The influence of cadence and power output on force application and in-shoe pressure distribution during cycling by competitive and recreational cyclists

The aim of this study was to determine the response of cyclists to manipulations of cadence and power output in terms of force application and plantar pressure distribution. Two groups of cyclists, 17 recreational and 12 competitive, rode at three nominal cadences (60, 80, 100 rev min -1 ) and four power outputs (100, 200, 300, 400 W) while simultaneous force and in-shoe pressure data were collected. Two piezoelectric triaxial force transducers mounted in the right pedal measured components of the pedal force and orientation, and a discrete transducer system with 12 transducers recorded the in-shoe pressures. Force application was characterized by calculating peak resultant and peak effective pedal forces and positive and negative impulses. In-shoe pressures were analysed as peak pressures and as the percent relative load. The force data showed no significant group effect but there was a cadence and power main effect. The impulse data showed a significant three-way interaction. Increased cadence resulted in a decreased positive impulse, while increased power output resulted in an increased impulse. The competitive group produced less positive impulse but the difference became less at higher cadences. Few between-group differences were found in pressure, notable only in the pressure under the first metatarsal region. This showed a consistent pattern of in-shoe pressure distribution, where the primary loading structures were the first metatarsal and hallux. There was no indication that pressure at specific sites influenced the pedal force application. The absence of group differences indicated that pressure distribution was not the result of training, but reflected the intrinsic relationship between the foot, the shoe and the pedal.     

The influence of cadence and power output on force application and in-shoe pressure distribution during cycling by competitive and recreational cyclists

The aim of this study was to determine the response of cyclists to manipulations of cadence and power output in terms of force application and plantar pressure distribution. Two groups of cyclists, 17 recreational and 12 competitive, rode at three nominal cadences (60, 80, 100 rev x min(-1)) and four power outputs (100, 200, 300, 400 W) while simultaneous force and in-shoe pressure data were collected. Two piezoelectric triaxial force transducers mounted in the right pedal measured components of the pedal force and orientation, and a discrete transducer system with 12 transducers recorded the in-shoe pressures. Force application was characterized by calculating peak resultant and peak effective pedal forces and positive and negative impulses. In-shoe pressures were analysed as peak pressures and as the percent relative load. The force data showed no significant group effect but there was a cadence and power main effect. The impulse data showed a significant three-way interaction. Increased cadence resulted in a decreased positive impulse, while increased power output resulted in an increased impulse. The competitive group produced less positive impulse but the difference became less at higher cadences. Few between-group differences were found in pressure, notable only in the pressure under the first metatarsal region. This showed a consistent pattern of in-shoe pressure distribution, where the primary loading structures were the first metatarsal and hallux. There was no indication that pressure at specific sites influenced the pedal force application. The absence of group differences indicated that pressure distribution was not the result of training, but reflected the intrinsic relationship between the foot, the shoe and the pedal.     

The influence of sitting posture on mechanics and metabolic energy requirements during sit-skiing: a case report

Several different sitting postures are used in Paralympic cross-country sit-skiing. The aim of this study was to evaluate the impact of sitting posture on physiological and mechanical variables during steady-state double-poling sit-skiing, as well as to determine how seat design can be improved for athletes without sufficient trunk control. Employing a novel, custom-designed seat, three trunk positions were tested while performing double-poling with submaximal oxygen consumption on an ergometer. Cycle kinematics, pole forces, and oxygen consumption were monitored. The athlete performed best, with longer cycle length and less pronounced metabolic responses, when kneeling with the trunk resting on a frontal support. For this case, a forward leaning trunk with knees below the hip joint was interpreted as most optimal, as it showed lower oxygen consumption and related parameters of performance during cross-country sit-skiing. Further investigations should examine whether such improvement is dependent on the level of the athlete’s handicap, as well as whether it is also seen on snow.     

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

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.     

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

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 x kg(-1) +/- 0.4) for the flat and 235 W +/- 10 (3.5 W x 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.     

Relationships between lower-limb kinematics and block phase performance in a cross section of sprinters

Abstract

This study investigated lower-limb kinematics to explain the techniques used to achieve high levels of sprint start performance. A cross-sectional design was used to examine relationships between specific technique variables and horizontal external power production during the block phase. Video data were collected (200 Hz) at the training sessions of 16 sprinters who ranged in 100 m personal best times from 9.98 to 11.6 s. Each sprinter performed three 30 m sprints and reliable (all intraclass correlation coefficients, ICC(2,3) ≥ 0.89) lower-limb kinematic data were obtained through manual digitising. The front leg joints extended in a proximal-to-distal pattern for 15 sprinters, and a moderate positive relationship existed between peak front hip angular velocity and block power (r = 0.49, 90% confidence limits = 0.08–0.76). In the rear leg, there was a high positive relationship between relative push duration and block power (r = 0.53, 90% confidence limits = 0.13–0.78). The rear hip appeared to be important; rear hip angle at block exit was highly related to block power (r = 0.60, 90% confidence limits = 0.23–0.82), and there were moderate positive relationships with block power for its range of motion and peak angular velocity (both r = 0.49, 90% confidence limits = 0.08–0.76). As increased block power production was not associated with any negative aspects of technique in the subsequent stance phase, sprinters should be encouraged to maximise extension at both hips during the block phase.     

空气动力学对场地自行车运动的影响

通过人、车风洞实验 ,测试 2人、3人和 4人跟骑时 ,空气阻力随风速、距离和侧面迎风骑行时的阻力变化。结果显示 ,2人正面跟骑时 ,将距离保持在 0 .30～ 0 .4 0m之间最为合适 ;高速骑行 2人跟骑距离在 0 .10～ 0 .2 0m时 ,后者对前者身后是尾流区 ,有干扰作用 ;运动员骑行时姿势角的变化 ,空气阻力值变化范围占人、车阻力的± 15 % ;3人和 4人跟骑时 ,最后 1人的空气阻力最小。     

女子自行车运动训练原则与方法的研究

本文就河南女子自行车队的成功经验,对女子自行车运动的训练原则与方法进行了探讨。     

场地自行车在直弯道之间的速度波动研究

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。     

自行车骑行对健康的影响及相关政策研究进展

自行车骑行是一项有利于健康的运动项目,在日常生活中鼓励人们更多地采用自行车代步出行和骑车锻炼对于促进公共健康、降低慢性疾病发病率具有重要意义。近年来许多国家和地区在大力推行自行车骑行和自行车复兴的政策、项目和规划。但自行车骑行同时也存在一些不利于健康的负面因素,通过在道路骑行中采取一些保护措施可以在一定程度上抵消道路骑行对健康的负面影响,达到骑行健身的效果。综述了近年来有关自行车骑行对健康的促进作用、与骑行有关的负面影响,以及国内外自行车骑行的现状,为与自行车有关的健康研究和政策制定提供理论依据。     

自行车运动场地项目原地起动技术动作的设计及其训练的实验研究

采用实验法、观察法等科研方法,以河南自行车队短距离项目组男、女运动员为实验对象,从生物力学角度重新设计改进了自行车场地项目原地起动技术动作,通过实践取得了很好的效果。     

试论自行车、铁人三项等赛事医疗急救和转运模式

通过总结分析三类高危体育赛事医疗急救和转运服务及急性伤病的案例资料,探索和研究行之有效的赛事医疗服务模式.应用实证研究和理论分析相结合的方法,回顾性地对1995年8月～2009年10月22场次自行车、铁人三项、摩托车赛事医疗急救和转运服务的思想理念、组织管理及赛事中突发的368例急性伤病的现场诊断救治进行了总结分析.赛事涉及国内国际、室内室外、陆地水中、高原平原、炎热寒冷、潮湿干旱、人体器械、耐力竞速、对抗性非对抗性、超长距离极短距离等因素,由政府、协会、企业等举办.急性伤病包括内科急症10类144例,外科急症7类224例;总转运率19.02%、总入院率14.40%,实现零死亡率和现场救治归队率80.98%.形成了 "超前预防、安全高效、和谐顺畅"思想理念模式; "规范化、科学化和国际化"组织管理模式:遵循国际惯例政策,制定个性化预案流程,"场(馆)运行团队"下的医疗团队"一盘棋"、"三人急救单元"模式,针对性培训演练,"医疗代表"模式; "标准化和专业化"现场急救和转运模式:遵循运动医学医疗服务道德准则和急救技术标准规范等,以"先救命、后治病"为主的评估诊断、实施救治、稳定病情的现场急救总则,各类急性伤病的现场急救和转运模式,院前创伤生命支持流程.为相关赛事医疗服务确立了切实可行的模式.促使了针对生命复杂体和具有"突发性、时效性、风险性、灵活性和实用性"的赛事医疗服务更加注重超前预防和运行中的简捷顺畅、规范精确、安全高效.这些模式成为了后续服务实践的基础.     

Cycling Nostalgia: Authenticity,Tourism and Social Critique in Tuscany

Over the last 15 years Italian cyclotourists have been building a subculture around nostalgia for vintage cycling (bici d'epoca). Vintage-inspired races and gatherings such as L'Eroica (the hero) in Tuscany serve as the ideological and organizational foundation of a kind of cyclotouring seeking to reclaim the values of an older and ‘purer’ form of the sport. Riders and enthusiasts dress in pre-1980s cycling clothing and are by regulation not allowed to ride bikes made after 1987, the year clipless pedals and aluminium and carbon fibre frames began mass production. Heroic cycling, as it has come to be called, draws on a history of social and political engagement by cyclotourists and cyclotouring clubs in Italy. The Touring Club Italiano (TCI), founded in 1894, began as a club for bourgeois gentlemen in Italy's North who had an interest in cycling. The TCI quickly became involved in the Liberal political causes of the moment and began advocating for better roads and an improved tourism industry. The TCI's goal of making ‘Italy known to Italians’ serves as the historic foundation of bici d'epoca which has attached itself to other contemporary sociopolitical causes in Italy seeking to undermine Europeanization and preserve Italian agricultural and artisanal heritages.     

中国自行车运动发展现状与训练学思考

通过文献资料法和专家访谈法,分析和论述了我国自行车运动发展的现状,并从改革赛制,奥运会备战过程中的战略重点的确立,科研信息保障以及训练理论和实践的创新等方面进行了论述,为2008年北京奥运会的备战工作提供了理论依据。     

The influence of isometric preload on power expressed during bench press in strength-trained men

The purpose of this study was to compare the power expressed during the bench press exercise in resistance-trained men following different pre-activation conditions. Twenty-two trained men (age 24.1?±?1.7 years, height 178.6?±?6.1?cm, body mass 81.1?±?10.6?kg) completed a maximal effort bench press (1-RM) test (100.0?kg?±?8.1?kg). In a subsequent assessment, each participant performed concentric bench press movements with loads of 20%, 30%, 40% and 50% of their 1-RM preceded by either a concentric contraction (CC), a low isometric preload (LIP; 70% 1-RM) or a high isometric preload (HIP; 100% 1-RM) conditions. All movements were performed in a Smith machine with a settable quick-release device. Participants performed all three conditions in randomized fashion. Results indicated that power outputs during the bench press exercise following HIP were significantly (p?<?0.05) greater than CC at 20% 1-RM (+9%), 30% 1-RM (+16%) and 40% 1-RM (+14%), and LIP at 20% 1-RM (+4%), 30% 1-RM (+20%) and 40% 1-RM (+15%). No differences were found between conditions at 50% 1-RM. Area under the force–power curve with HIP was greater (p?<?0.05) than with CC and LIP. In conclusion, results of this study indicate that the use of a HIP (100% 1-RM) in trained participants results in significantly greater power output during the concentric phase of a multi-joint exercise when compared to standard concentric movement.     

Familial aggregation of aerobic power: the influence of age, physical activity, and body mass index

Whereas modest familial aggregation of VO2max has been documented after controlling for variables such as physical activity habits, the effect of adjustment for moderating variables has not been directly tested. This issue was addressed in 95 Anglo and 111 Mexican-American families who underwent submaximal cycle ergometer testing. Zero-order correlations of predicted VO2max between pairs of family members were generally weak for both Anglo families (r = 0.04 to 0.35) and Mexican-American families (r = 0.03 to 0.50). Five of 12 correlations were significant. Similar results were found for combined ethnic groups. Adjustment for age, physical activity, and body mass index by partial correlation had few significant effects on aggregation of predicted VO2max. Adjustment for body mass index produced significant decreases in the correlation for Anglo spouses and mother-older child and sibling pairs in the combined group. Although influential moderating variables were not identified, body mass index was found to be a significant, though inconsistent, mediator of aggregation of VO2max. Genetic factors were not strongly supported because of generally weak aggregation in the two ethnic groups.     

自行车运动训练测试台的研制

微机控制的自行车运动员综合训练测试系统,可提供运动员在特制的训练台上骑行,台上装有模拟阻力和测速装置,还设置有脚蹬力和多种测角装置,可同步检测各种力值与角度并实时处理。骑行中由模拟显示盘显示诱导、骑行的轨迹信号和骑行参数。系统配有三套软件可进行诊断、检测和诱导。可屏幕分析或储存打印。