Automatic measurement of key ski jumping phases and temporal events with a wearable system

We propose a new method, based on inertial sensors, to automatically measure at high frequency the durations of the main phases of ski jumping (i.e. take-off release, take-off, and early flight). The kinematics of the ski jumping movement were recorded by four inertial sensors, attached to the thigh and shank of junior athletes, for 40 jumps performed during indoor conditions and 36 jumps in field conditions. An algorithm was designed to detect temporal events from the recorded signals and to estimate the duration of each phase. These durations were evaluated against a reference camera-based motion capture system and by trainers conducting video observations. The precision for the take-off release and take-off durations (indoor < 39 ms, outdoor = 27 ms) can be considered technically valid for performance assessment. The errors for early flight duration (indoor = 22 ms, outdoor = 119 ms) were comparable to the trainers' variability and should be interpreted with caution. No significant changes in the error were noted between indoor and outdoor conditions, and individual jumping technique did not influence the error of take-off release and take-off. Therefore, the proposed system can provide valuable information for performance evaluation of ski jumpers during training sessions.     

利用能量单位评价跑步经济性的有效性研究

目的:利用便携式肺功能仪,在场地条件下测试中跑运动员4种次极限跑速时的跑步经济性(RE),比较以时间耗氧(ml/kg/min)、距离耗氧(ml/kg/km)和距离耗能(kcal/kg/km)单位评价RE的有效性。方法:10名中跑运动员在标准田径场跑道上完成1次递增负荷测试和1次持续4个回合的恒定负荷测试。通过递增负荷测试获取最大耗氧量(VO2max)和无氧阈(AT),并分别以70%、80%、90%、105%AT强度完成5～10min恒定负荷测试,取稳态耗氧量及相关呼吸指标计算3种不同单位表示时的RE。结果:3种单位表示的RE在两两间均呈现出非常显著的相关关系(P<0.01)。随运动强度的增高,单位时间的耗氧在每级间均显著增高(P<0.05);单位距离的耗氧则无明显变化(P>0.05),且在80%～105%AT强度间出现微弱的降低;单位距离的能耗在70%～90%AT间缓慢增高(P>0.05),但在90%～105%AT间增高显著(P<0.05);呼吸交换率(RER)则在80%～105%AT间出现了不同程度地显著提高(80%～90%AT:P<0.05,90%～105%AT:P<0.01)。结论:无论是时间耗氧单位还是距离耗氧单位,都忽略了底物利用的不同对耗氧量的影响,无法有效评定RE。能量单位更符合RE的本质特征,与运动实践更加相关,是评定RE的有效单位。     

我国优秀男子手球运动员比赛跑动特征研究

手球比赛属于集体球类对抗性项目,比赛跑动能力体现出技术、战术、体能等诸多因素,是比赛制胜的重要因素。对我国男子手球运动员在男子手球联赛、十一届全运会以及第16届亚运会等大型赛事的备战和系列比赛展开研究,结果表明:1)不同位置运动员全场跑动总距离在3 951～4 552m之间,平均为4 249m,跑动距离最多的是边锋,最少的是内锋。2)冲刺跑和高速跑动距离最多的是边锋,最少的是中锋;中速跑动距离最多的是边锋,最少的是中锋;低速跑动距离最多的是中锋,最少的是边锋;慢跑距离最多的是组织,最少的是边锋;走动距离最多的是边锋,最少的是组织。3)手球运动员的全场跑动轨迹是以各位置运动员在两个进攻区域之间以近似直线式的轨迹活动。4)全场进攻和防守的跑动次数分别为70次和78次,平均每25s会有一次跑动,不分速度的情况下平均每次移动的距离为28.71m。     

高三女生800m跑施行单元教学与体能提高的实验研究

本文通过对高三年级女生施行耐久跑单元教学法结合娱乐教学的实验研究,激发了学生良好的学习兴趣,学生的体能有了显著性提高,实验证明耐久跑单元教学对提高高中女生800m跑成绩有着较好的教学效果。     

分析比较中外短跑运动员途中跑技术的差异

通过文献资料、分析对比等方法,对短跑途中跑技术进行分析,发现我国运动员在途中跑“后蹬屈膝式”技术及放松、步幅、节奏等技术方面与国外优秀选手存在一定差距。     

Maximal lactate steady state in trained adolescent runners

The aims of this study were: (1) to identify the exercise intensity that corresponds to the maximal lactate steady state in adolescent endurance-trained runners; (2) to identify any differences between the sexes; and (3) to compare the maximal lactate steady state with commonly cited fixed blood lactate reference parameters. Sixteen boys and nine girls volunteered to participate in the study. They were first tested using a stepwise incremental treadmill protocol to establish the blood lactate profile and peak oxygen uptake ([Vdot]O₂). Running speeds corresponding to fixed whole blood lactate concentrations of 2.0, 2.5 and 4.0?mmol?·?l^?1 were calculated using linear interpolation. The maximal lactate steady state was determined from four separate 20-min constant-speed treadmill runs. The maximal lactate steady state was defined as the fastest running speed, to the nearest 0.5?km?·?h^?1, where the change in blood lactate concentration between 10 and 20?min was?<0.5?mmol?·?l^?1. Although the boys had to run faster than the girls to elicit the maximal lactate steady state (15.7 vs 14.3?km?·?h^?1, P?<0.01), once the data were expressed relative to percent peak [Vdot]O₂ (85 and 85%, respectively) and percent peak heart rate (92 and 94%, respectively), there were no differences between the sexes (P?>0.05). The running speed and percent peak [Vdot]O₂ at the maximal lactate steady state were not different to those corresponding to the fixed blood lactate concentrations of 2.0 and 2.5?mmol?·?l^?1 (P?>0.05), but were both lower than those at the 4.0?mmol?·?l^?1 concentration (P?<0.05). In conclusion, the maximal lactate steady state corresponded to a similar relative exercise intensity as that reported in adult athletes. The running speed, percent peak [Vdot]O₂ and percent peak heart rate at the maximal lactate steady state are approximated by the fixed blood lactate concentration of 2.5?mmol?·?l^?1 measured during an incremental treadmill test in boys and girls.     

Changes in locomotive rates during senior elite rugby league matches

Abstract

The aim of this study was to quantify the changes in locomotive rates across the duration of senior elite rugby league matches. A semi-automated image recognition system (ProZone 3, ProZone®, Leeds, England) was used to track the movements of 59 players from six teams during three competitive matches. The players were classified into one of four positional groups: props (n = 9), back row (n = 9), pivots (n = 14) or outside backs (n = 27). Players' movements were classified as low, high or very high intensity running and reported as locomotive rates (distance covered per minute played) for successive quarters of each match. Analysis of variance revealed that only the outside backs showed a significantly lower overall locomotive rate during the final quarter compared to the first (P < 0.05). However, locomotive rates for high and very high intensity running during the final quarter were significantly lower (P < 0.05) than the first quarter among outside backs, pivots and props despite no change in the rate of involvements in contact. On the basis of these findings, it is suggested that high and very high intensity running locomotive rates may be more affective methods of detecting fatigue during competitive matches than overall locomotive rate.     

少年女子短跑运动员途中跑支撑时间及影响因素

运用运动学与动力学理论，对少年女子短跑和跳跃项目运动员短跑途中跑支撑时间及相关影响因素进行研究。结果表明：支撑时间和年龄不相关，而是随速度提高而缩短；影响支撑时间的因素为技术、身高、快速力量和速度。通过与世界优秀运动员支撑时间比较显示：少年女子运动员支撑时间较长，腾空／支撑时间值小，前支撑／支撑时间值大，高水平运动员与此相反。认为：缩短支撑时间、形成各种合理时间特征比例是提高最大跑速的关键；在考察支撑时间对速度影响时，还应综合考虑身体结构和身高等因素。     

短跑400m项目的速度与速度耐力因素分析

400m跑是典型的速度耐力性运动项目。通过文献资料方法,对世界记录保持者迈克尔.约翰逊及第7届世界田径锦标赛400m跑前二名运动员和我国男子优秀400m运动员的分析研究,说明速度与速度耐力因素对400m跑成绩的影响。     

青少年400m运动员训练手段与应注意的问题

本文根据400m运动项目和青少年运动员身体发育的特殊情况,并通过查阅相关文献资料,总结了近些年来国内青少年400m运动员训练的手段和在训练中应注意的问题。希望通过本文的研究,能为我国青少年400运动训练水平的提高提供理论依据。