推铅球动作系统的生物力学分析

运用运动生物力学等基础理论，对推铅球技术的连续图片进行综合分析。提出了激发肌肉潜能，加速动作节奏，以适宜的角度、合理的高度和最快的出手初速度投掷铅球的规范动作标准。     

Swimming

Abstract

The effect on drag of a Speedo Fast‐skin suit compared to a conventional suit was studied in 13 subjects (6 males, 7 females) swimming at different velocities between 1.0 and 2.0 m?s^‐1. The active drag force was directly measured during front crawl swimming using a system of underwater push‐off pads instrumented with a force transducer (MAD system). For a range of swimming speeds (1.1, 1.3, 1.5 and 1.7 m?s^‐1), drag values were estimated. On a group level, a statistically non‐significant drag reduction effect of 2% was observed for the Fast‐skin suit (p = 0.31). Therefore, the 7.5% reduction in drag claimed by the swimwear manufacturer was not corroborated.     

Kinematics of side and cross circles on pommel horse

Abstract

One of the most fundamental skills on the pommel horse is double leg circles (circles). Circles can be performed on all parts of the pommel horse. It was hypothesized that the different sets of physical constraints of the apparatus require a gymnast to adapt circles technique. The purpose of this study was to quantify how gymnasts modify their technique during circles to accommodate different physical obstacles due to different support surfaces and body orientations. To investigate these adaptations, a comparison of the two most common circles on pommel horse – namely, circles in cross support (cross-circles) and circles in side support (side-circles) – was carried out. Seven elite male gymnasts performed three sets of 10 cross-circles and side-circles on a pommel horse. Three-dimensional coordinates were acquired using 12 Qualisys ProReflex motion tracking cameras operating at 120 Hz. Temporal characteristics, the motion of the centre of mass, and the body angles – flexion and lateral flexion – were analysed. We found that cross-circles took less time to complete a single circle (0.92±0.02 vs. 0.95±0.02 s), had a smaller ratio for the rear support phase (0.15±0.02 vs. 0.18±0.03), a narrower supporting-hand distance (0.33±0.03 vs. 0.52±0.00 m), greater flexion of the body over the rear support phase (44±12° vs. 27±8°), and less lateral flexion of the body over the single-hand support phase (entry: 20±5° vs. 35±3°; exit: 26±4° vs. 33±4°) than side-circles. Our results suggest that gymnasts adapt their technique to the physical constraints imposed by the shape of the pommel horse and the location and orientation of the circles. Cross-circles were characterized by a high rear support position with a narrower hand-spacing, which would require excellent shoulder flexibility and strength. Consequently, lack of these traits may explain the need for greater body flexion in cross-circles than in side-circles during rear support. Understanding the technical differences will facilitate an effective transfer of the technical similarities among different types of circles.     

背越式跳高运动员摆动腿技术对起跳效果的影响

跳高是体能主导类项目,但对技术要求较高的运动项目,跳的更高是每位跳高运动员所追求的目标。目前,我国跳高项目举步维艰的现实让我们不禁思考如何改进此项目在技术上的不足。本文着重对跳高运动员摆动腿技术的研究成果进行总结和归纳,提取背越式跳高运动员摆动腿技术的有效训练方法和经验,为跳高技术教学与训练提供理论和实践依据。     

Active recovery effects by previously inactive muscles on 40-s exhaustive cycling

Abstract

The effects of active recovery using previously active and inactive muscle groups on power output and respiratory responses were examined. Ten male volunteers underwent two exhaustive 40-s bouts of leg cycling (1st Ex and 2nd Ex), separated by a 20-min recovery period. The recovery conditions were leg (Leg-Active) or arm (Arm-Active) cranking at 50% ventilatory threshold (VT), or sedentary control (Passive). The total output work (Total work) during the 2nd Ex in the Leg-Active condition was significantly higher than that in the Passive (299 vs. 282 J · kg body mass^?1 (J · BM^?1)). The values of Total work, peak [Vdot]O₂ and peak heart rate during the 2nd Ex were significantly higher than those during the 1st Ex in both Leg- and Arm-Active. Total CO₂excess after the 1st Ex was significantly higher than that after the 2nd Ex (67.6 vs. 26.0 ml · BM^?1) in Passive. After the 2nd Ex, the Total CO₂excess in the Leg-Active (51.5 ml · BM^?1) was significantly higher than that in both the Passive (26.0) and Arm-Active (36.5), with Arm-Active being significantly higher than Passive. The recovery exercise using previously inactive muscles improved respiratory compensation ability related to performance enhancement.     

Isokinetic Leg Flexion and Extension Strength of Elite Adolescent Female Track and Field Athletes

Abstract

Sixty-two elite adolescent (age: 16.39 ± 1.62 yrs) female track and field athletes volunteered to be measured isokinetically for peak torque of the leg flexors and extensors. The sample included 16 throwers, 11 jumpers, 12 middle-distance runners (> 400 m), and 23 sprinters. A Cybex II isokinetic dynamometer was used to measure dominant leg strength at 180°/sec. One-way ANOVA revealed significant between group differences for absolute flexion and extension (Nm), extension/body weight (Nm/Kg), and extension/lean body weight (Nm/Kg). Scheffe post-hoc comparisons showed that, for absolute leg extension strength, throwers were stronger than middle-distance runners (by 54.4%), sprinters (35.6%), and jumpers (23.6%). For absolute leg flexion movements, throwers were stronger than middle distance runners (37.4%) and sprinters (32.1%). Jumpers had greater extension peak torque values than middle-distance runners relative to body weight (14.0%), and throwers were stronger than middle-distance runners for extension/lean body weight (14.9%)). No other comparisons were significant. However, when strength was expressed relative to body weight or lean body weight, there were few differences between events for flexion or extension. Given that absolute strength scores were correlated with body weight and lean body weight, peak torque/body weight or peak torque/lean body weight may be more sensitive than absolute values as indicators of underlying factors (such as training status or fiber type composition) responsible for the differences in muscular strength between groups.     

CIP-I智能人工腿步速控制系统硬件设计

CIP-I Leg是国内首个智能仿生人工腿原型机。针对智能仿生人工腿应能模仿人体健康腿的运动方式且步行速度可自然、随意地跟随截肢者步行速度的变化而变化的重要特点,同时考虑到高精度、低功耗和抗干扰能力强等,设计了一种基于新型超低功耗微处理器MSP430F149的人工腿步速控制系统硬件电路。实验结果表明,所设计的步速控制系统运行可靠、功耗低、精度高,可有效地用于自行设计的CIP-I Leg的控制。     

“立法正确”的神话之破解

“立法正确”的神话诞生于近代西方工业化的扩展和民族国家的形成,以“新国家学说”所主张的形式与内容相分离为理论基础。首先,它主张立法形式的正确性,要么将立法内容交由权力决定,使“恶法亦法”成为题中应有之义;要么认为内容出自形式,这纵然令人向往,但终究是个“神”的问题。其次,它假定立法内容的正确性,立法者不颁布“卑鄙的”法律,德国民族社会主义的立法实践,使这一假定成为彻底破灭的神话。“立法正确”的基本神话,可推出另外两个神话：（1）禁止法官造法和准确把握立法原意;（2）启蒙百姓懂法。同样,这两个神话也是永远不能实现的。文章还探讨了“立法正确”的神话破灭后之可能出路：一是人民的反抗权难题;二是法官如何以理释法。     

唐末五代宋初的食人现象--兼说中国古代食人现象与文化陋俗的关系

唐末五代宋初,食人现象不绝于史.这既有当时社会动乱,野蛮、愚昧肆行的历史原因,也与印度佛教东传后割股疗亲风俗的兴起、古代人祭遗风仍存有关.宋初统治者"崇风俗,敦教化",惩治食人恶习,才使这一现象逐渐减少乃至消失.     

男子二级跳远运动员起跳阶段摆动腿技术的运动学分析

文章运用文献资料、数理统计和图像解析的研究方法,对二级跳远运动员的运动学指标进行研究。结果表明：（1）二级运动员起跳时间平均值是0.130s,缓冲时间平均值为0.048s,蹬伸时间平均值0.082s。缓冲时间、蹬伸时间与整个起跳时间过长。这与二级运动员本身身体素质和技术动作的优劣存在很大关系;（2）二级运动员着板瞬间,摆动腿的摆动角速度平均值为451.72°/s,膝关节角度平均为87.14°上板速度为8.58m/s,与前人的研究有出入;（3）二级运动员速度利用率为76.30%,速度利用率明显低于优秀运动的速度利用率。腾起角平均为26.66°,明显高于优秀运动员的18°-25°;（4）在蹬伸阶段摆动角速度的最大值与腾起角和成绩明显正相关。