Independence of reaction time and response force control during isometric leg extension     

Tatsuyuki Ohtsuki ‡ 《Journal of sports sciences》2013,31(4):373-382

In this study, we examined the relative control of reaction time and force in responses of the lower limb. Fourteen female participants (age 21.2±1.0 years, height 1.62±0.05?m, body mass 54.1±6.1?kg; mean±s) were instructed to exert their maximal isometric one-leg extension force as quickly as possible in response to an auditory stimulus presented after one of 13 foreperiod durations, ranging from 0.5 to 10.0?s. In the ‘irregular condition’ each foreperiod was presented in random order, while in the ‘regular condition’ each foreperiod was repeated consecutively. A significant interactive effect of foreperiod duration and regularity on reaction time was observed (P?<?0.001 in two-way ANOVA with repeated measures). In the irregular condition the shorter foreperiod induced a longer reaction time, while in the regular condition the shorter foreperiod induced a shorter reaction time. Peak amplitude of isometric force was affected only by the regularity of foreperiod and there was a significant variation of changes in peak force across participants; nine participants were shown to significantly increase peak force for the regular condition (P?<?0.001), three to decrease it (P?<?0.05) and two showed no difference. These results indicate the independence of reaction time and response force control in the lower limb motor system. Variation of changes in peak force across participants may be due to the different attention to the bipolar nature of the task requirements such as maximal force and maximal speed.  相似文献   

Insulin sensitivity derived from oral glucose tolerance testing in athletes: Disagreement between available indices     

Konstantinos Niakaris  Faidon Magkos  Nikos Geladas  Labros S Sidossis 《Journal of sports sciences》2013,31(10):1065-1073

The aims of the present study were to determine whether available “fasting” and oral glucose tolerance test-derived insulin sensitivity indices could effectively discriminate between individuals with higher than normal insulin sensitivity, and whether they would all provide similar information in clinical practice. Sprint runners (n = 8), endurance runners (n = 8) and sedentary controls (n = 7) received a 75-g oral glucose tolerance test. All participants were healthy lean males, aged 21?–?29 years. Besides glucose and insulin responses, a total of nine such indices were computed. Fasting as well as post-load glucose concentrations were similar in the three groups, while basal plasma insulin and the insulinaemic response to glucose were both higher in untrained individuals (at P?<?0.05 and P?<?0.02, respectively). There were no differences between endurance and sprint runners. The results for insulin sensitivity, however, were quite variable: three indices showed that both groups of athletes were more insulin-sensitive than controls; three indicated that this was the case for endurance runners only; one indicated that this was the case for sprint runners only; and two showed that sprint runners were more insulin-sensitive than either sedentary individuals or endurance runners (all differences were significant at P?<?0.05). Controlling for total body weight or lean mass did not effectively resolve this disagreement. Apparently, the various insulin sensitivity indices examined provided different quantitative and qualitative information, despite insulin action being greater in both groups of athletes relative to controls, as reflected by their similar glucose tolerance with lower insulin concentrations. We suggest, therefore, that the use and interpretation of such indices among physically active individuals be made with caution.  相似文献   

Time–motion analysis of elite field hockey,with special reference to repeated-sprint activity     

Matt Spencer  Steven Lawrence  Claire Rechichi  David Bishop  Brian Dawson  Carmel Goodman 《Journal of sports sciences》2013,31(9):843-850

Limited information exists about the movement patterns of field-hockey players, especially during elite competition. Time–motion analysis was used to document the movement patterns during an international field-hockey game. In addition, the movement patterns of repeated-sprint activity were investigated, as repeated-sprint ability is considered to be an important fitness component of team-sport performance. Fourteen members of the Australian men's field-hockey team (age 26±3 years, body mass 76.7±5.6?kg, [Vdot]O_2max 57.9±3.6?ml?·?kg^?1?·?min^?1; mean±s) were filmed during an international game and their movement patterns were analysed. The majority of the total player game time was spent in the low-intensity motions of walking, jogging and standing (46.5±8.1, 40.5±7.0 and 7.4±0.9%, respectively). In comparison, the proportions of time spent in striding and sprinting were 4.1±1.1 and 1.5±0.6%, respectively. Our criteria for ‘repeated-sprint’ activity (defined as a minimum of three sprints, with mean recovery duration between sprints of less than 21?s) was met on 17 occasions during the game (total for all players), with a mean 4±1 sprints per bout. On average, 95% of the recovery during the repeated-sprint bouts was of an active nature. In summary, the results suggest that the motion activities of an elite field-hockey competition are similar to those of elite soccer, rugby and Australian Rules football. In addition, the investigation of repeated-sprint activity during competition has provided additional information about the unique physiological demands of elite field-hockey performance.  相似文献   

Sprint mechanical differences at maximal running speed: Effects of performance level     

Giorgios P Paradisis  Athanassios Bissas  Panagiotis Pappas  Elias Zacharogiannis  Apostolos Theodorou  Olivier Girard 《Journal of sports sciences》2013,31(17):2026-2036

ABSTRACT

As the effect of performance level on sprinting mechanics has not been fully studied, we examined mechanical differences at maximal running speed (MRS) over a straight-line 35 m sprint amongst sprinters of different performance levels. Fifty male track and field sprinters, divided in Slow, Medium and Fast groups (MRS: 7.67 ± 0.27 m?s^?1, 8.44 ± 0.22 m?s^?1, and 9.37 ± 0.41 m?s^?1, respectively) were tested. A high-speed camera (250 Hz) recorded a full stride in the sagittal plane at 30–35 m. MRS was higher (p < 0.05) in Fast vs. Medium (+11.0%) and Slow (+22.1%) as well as in Medium vs. Slow (+10.0%). Twelve, eight and seven out of 21 variables significantly distinguished Fast from Slow, Fast from Medium and Medium from Slow sprinters, respectively. Propulsive phase was signi?cantly shorter in Fast vs. Medium (?17.5%) and Slow (?29.4%) as well as in Medium vs. Slow (?14.4%). Fast sprinters had significantly higher vertical and leg stiffness values than Medium (+44.1% and +18.1%, respectively) and Slow (+25.4% and +22.0%, respectively). MRS at 30–35 m increased with performance level during a 35-m sprint and was achieved through shorter contact time, longer step length, faster step rate, and higher vertical and leg stiffness.  相似文献   

Cardiac Dimensions in Elite Young Track Athletes     

Gerald D. Tharp  William G. Thorland  Glen O. Johnson  James B. Peter 《Research quarterly for exercise and sport》2013,84(2):139-143

The purpose of the study was to compare young sprint and distance runners for changes in their cardiac dimensions with increased age (10–17 years) or body surface area (1–2 m²). Echocardiographic dimensions were obtained on 73 male track athletes competing in the 1983 National Age Group Track and Field Association championships. Each group of athletes was also compared with a hypothetical normal population (matched for weight and age) generated from prediction equations derived by Henry, Gardin, & Ware (1980). The cardiac dimensions examined were: Left ventricular internal diameter, left ventricular posterior wall thickness, and interventricular septum thickness. The male distance runners (n = 38) had a significantly greater increase in left ventricular posterior wall thickness and interventricular septum thickness with increasing age or increasing body surface area compared to the sprinters (n = 35) or compared to the predicted normal population. The left ventricular internal diameter was not significantly different between the groups. These results indicate that the hearts of male distance runners are undergoing a training hypertrophy whereas the hearts of sprinters are no different than hearts in a normal population. The changes in cardiac dimensions of these young athletes run counter to the generalizations stated for adult athletes: That endurance training enlarges the left ventricular internal diameter, but does not increase the left ventricular posterior wall or interventricular septum thickness.  相似文献   

Lower limb joint kinetics during the first stance phase in athletics sprinting: three elite athlete case studies     

Neil Edward Bezodis  Aki Ilkka Tapio Salo  Grant Trewartha 《Journal of sports sciences》2013,31(8):738-746

Abstract

This study analysed the first stance phase joint kinetics of three elite sprinters to improve the understanding of technique and investigate how individual differences in technique could influence the resulting levels of performance. Force (1000 Hz) and video (200 Hz) data were collected and resultant moments, power and work at the stance leg metatarsal-phalangeal (MTP), ankle, knee and hip joints were calculated. The MTP and ankle joints both exhibited resultant plantarflexor moments throughout stance. Whilst the ankle joint generated up to four times more energy than it absorbed, the MTP joint was primarily an energy absorber. Knee extensor resultant moments and power were produced throughout the majority of stance, and the best-performing sprinter generated double and four times the amount of knee joint energy compared to the other two sprinters. The hip joint extended throughout stance. Positive hip extensor energy was generated during early stance before energy was absorbed at the hip as the resultant moment became flexor-dominant towards toe-off. The generation of energy at the ankle appears to be of greater importance than in later phases of a sprint, whilst knee joint energy generation may be vital for early acceleration and is potentially facilitated by favourable kinematics at touchdown.  相似文献   

2013年速滑短距离世锦赛分析与备战索契冬奥会的对策     

吴震  陈月亮  冯庆波 《冰雪运动》2013,(2):1-9

通过对2013年美国盐湖城速度滑冰短距离世锦赛成绩的统计分析,对比国内外选手的优势与不足,探寻我国短距离速滑运动员存在的主要差距、努力方向和训练重点。针对我国选手存在的问题,提出针对性的解决方案,并对备战索契冬奥会进行了展望,从明确备战目标、制定好训练与参赛计划、精心选择训练策略等方面,探讨了备战索契冬奥会的对策,以期为备战2014年索契冬奥会提供参考意见。  相似文献   

Effect of the coefficient of friction of a running surface on sprint time in a sled-towing exercise     

Nicholas P. Linthorne  James E. Cooper 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(2):175-185

This study investigated the effect of the coefficient of friction of a running surface on an athlete's sprint time in a sled-towing exercise. The coefficients of friction of four common sports surfaces (a synthetic athletics track, a natural grass rugby pitch, a 3G football pitch, and an artificial grass hockey pitch) were determined from the force required to tow a weighted sled across the surface. Timing gates were then used to measure the 30-m sprint time for six rugby players when towing a sled of varied weight across the surfaces. There were substantial differences between the coefficients of friction for the four surfaces (μ = 0.21–0.58), and in the sled-towing exercise the athlete's 30-m sprint time increased linearly with increasing sled weight. The hockey pitch (which had the lowest coefficient of friction) produced a substantially lower rate of increase in 30-m sprint time, but there were no significant differences between the other surfaces. The results indicate that although an athlete's sprint time in a sled-towing exercise is affected by the coefficient of friction of the surface, the relationship relationship between the athlete's rate of increase in 30-m sprint time and the coefficient of friction is more complex than expected.  相似文献   

高水平400 m运动员有效训练负荷研究——兼论中美400 m训练理念之异同   总被引：3，自引：0，他引：3  

黄毅  王宇红  蔡勇 《北京体育大学学报》2008,31(7)

从训练学角度对400 m项目的"有效训练负荷"问题进行研究。提出了高水平400 m运动员的训练负荷体系应是围绕着无氧乳酸训练负荷为核心的,无氧非乳酸速度训练及专项身体训练为主要支持系统的负荷系统。美国教练较为平稳的负荷走势设计与我国"跳跃式"的负荷设计有较大不同,对超量恢复理论提出了挑战。"多次乳酸强度训练"的有效性应是衡量400 m项目训练负荷设计有效性的重要标准等结论。  相似文献   

中学生短跑协调放松能力培养的实验研究   总被引：2，自引：0，他引：2  

夏琼华 《首都体育学院学报》2008,20(6)

协调放松能力的培养是中学生短跑训练中不可或缺的重要部分,协调放松训练是中学生完成动作质量的保障;有助于增大中学生短跑运动员肌肉的收缩力量和收缩速度,并有效提高中学生短跑成绩。运用实验法,对广州市第一中学16名中学生进行为期2个月的短跑训练研究,发现目前对中学阶段短跑运动员的短跑协调放松能力培养重视不够,且缺少系统完整的训练方法。通过对这些现象分析研究提出了对中学生短跑协调放松能力培养的手段和方法,旨在对原有的中学生短跑训练方法做相应补充与改进,从而提高中学生的短跑成绩。  相似文献