跳跃性应力刺激对大鼠血清 PTH 及骨代谢相关分子 OPG、RANKL 的影响

目的：研究长期跳跃应力刺激对甲状腺激素(PTH)和骨代谢相关分子基因表达的影响,探讨跳跃运动所致的骨质破坏发生分子机制。方法：48只8周龄雄性 SD 大鼠,随机分为对照组、跳跃组和负重跳跃组,运动2周后每组取材8只,记为 C2、J2和JL2,运动6周后各组,记为 C6、J6和 JL6。跳跃组进行递增负荷跳跃运动,负重跳跃组负重5%自身体重,运动方案同跳跃组。采用酶联免疫吸附试验(ELISA)检测血清甲状旁腺激素(PTH),采用比色法检测血清碱性磷酸酶(ALP)和抗酒石酸酸性磷酸(StrACP)含量。取一侧胫骨制作 HE 石蜡切片,另一侧应用 RT - PCR 法检测 OPG、RANKL 的 mRNA 表达。结果：(1)与 C6和 J6组相比,JL6组骨胶原纤维和骨膜排列紊乱,骨皮质出现较大程度破坏,空腔增多。(2)JL6组血清 ALP 高于 J6和 C6组(p <0.01,p <0.05)。JL6组和 J6组 StrACP 显著高于 C6组(p <0.01)。(3)J2和 JL2 PTH 水平组显著低于 C2组(p <0.05,p <0.01),JL6组低于 J6和C6组(p <0.05,p <0.01)。(4)与 C6组比较,J6组和 JL6组 OPGmRNA 表达显著升高,其中 J6组表达量最高。 JL6组 RANKL 表达显著高于 J6和 C6组(p <0.01),J6组 RANKL 的表达高于 C6组(p <0.05)。结论：负重跳跃运动6周后大鼠胫骨骨质破坏较为严重,骨代谢以骨转换率升高为特征,RANKL 的持续升高可能是骨质破坏的重要原因,而血清 PTH 水平持续下降不利于骨质修复。     

装钢机自动控制系统的应用

本文介绍了河北钢铁集团唐钢热轧1700mm生产线中加热炉装钢机系统的设备构成,控制方式,运行顺序,参数计算等。整套控制系统结构简单,成本低廉,抗干扰性好,便于调试。     

Kinematic and kinetic differences in the execution of vertical jumps between people with good and poor ankle joint dorsiflexion

Abstract

The aim of the present study was to investigate the kinematic and kinetic differences in the execution of vertical jumps between individuals with good and poor ankle dorsiflexion. Fifteen physical education students were assigned to the flexible group (FG), while another 15 were assigned to the inflexible group (IFG). The two groups executed countermovement jumps (CMJ) and drop jumps from a 60 cm height (DJ60). For the CMJ, the FG jumped higher (32.0 ± 4.0 cm vs. 30.2 ± 4.9 cm, P = 0.27) and used a greater range of motion in all leg joints. The IFG jumpers raised their heels off the ground and had a greater horizontal distance between the centre of mass of the trunk and the centre of the hip joint (L_CMh 25.6 ± 3.4 cm vs. 30.9 ± 4.3 cm, P < 0.001). In the DJ60 the FG jumped higher (22.4 ± 5.9 cm vs. 19.5 ± 4.6 cm, P = 0.14) with a greater vertical shift of the body centre of mass (BCM) (S = 0.45 ± 0.11 cm vs. 0.36 ± 0.05 cm, P < 0.01) and better joint coordination. The IFG jumpers changed the position of their trunk and heels depending on the jump type. Trainers should reconsider the technical issues of vertical jumps according to the flexibility of the ankle joint.     

Acute whole-body vibration does not affect static jump performance

Abstract

Currently, whole-body vibration is being used to promote enhanced performance. Many coaches and athletes believe that it can acutely enhance explosive performance and power output. However, the scientific literature is unclear as to whether this enhancement occurs. The purpose of this study was to examine the acute effects of whole-body vibration on static jump performance, including jump height, peak force, rate of force development, and peak power. Fourteen recreationally active individuals (5 females, 9 males) participated in three separate randomized treatment sessions. Treatment 1 consisted of no vibration while treatment 2 and treatment 3 incorporated whole-body vibration. The whole-body vibration protocol consisted of three 30-s bouts of vibration performed at 30 Hz and low amplitude (~3 mm) with a 30-s rest between bouts. Treatment 1 was identical in duration to both treatments 2 and 3, but did not contain any vibration. Five minutes after each treatment, the participants performed the static jump protocols. Two (data averaged) non-weighted static jumps and two 20 kg weighted jumps were performed. Treatments 1 vs. 2, 1 vs. 3, and 2 vs. 3 were calculated for each variable at both 0 kg and 20 kg. Jump height, peak force, rate of force development, and peak power were analysed using a one-way analysis of variance with repeated measures. The intra-class correlations comparing the two trials of each jump for each of the three treatments were ≥0.92. Compared with the no-vibration condition, jump height showed a non-significant increase as a result of whole-body vibration for both unweighted and weighted jumps; peak force, rate of force development, and peak power were not statistically different. The results indicate that whole-body vibration has no effect on jump height, peak force, rate of force development or peak power during static jumping.     

NBA与CBA比赛跳跃步法的对比分析

通过录像分析了NBA与CBA各8场比赛,对比CBA与NBA比赛中各个位置队员使用各种跳跃步法的差异。将跳跃步法按原地起跳、一步助跑起跳、两步以上单脚起跳、两步以上双脚起跳、后撤步起跳、连续起跳、横向移动急停起跳等7种方式进行了归类和统计。结果发现CBA队员比NBA队员更多地采用了原地起跳,而在一步助跑起跳与两步以上助跑双脚起跳的使用频率上比NBA低。相差最大的是横向移动急停起跳,NBA的控球后卫、得分后卫、小前锋使用该步法的频率分别是CBA相同队员的1.6倍、2.1倍、3.9倍。提示：CBA队员应该增加运动中起跳的次数,尤其要加强对横向移动急停起跳的训练与应用。同时要加强对横向移动急停起跳的生物力学研究,为提高训练效果、预防损伤、研发符合篮球运动特点的篮球鞋提供理论依据。     

对《田径竞赛规则》中有关抢跑规则的再研究

通过调查分析 ,对现行《田径竞赛规则》中有关抢跑的规则提出了疑义 ,并提出了在国内中、小型比赛中第 1次抢跑犯规以后 ,无论哪个运动员再抢跑犯规 (不论该运动员是第几次犯规 )均应取消比赛资格和在国际比赛、国内大型比赛中使用一次性起跑规则的建议     

Aerodynamic force data for a V-style ski jumping flight

To determine the flight of a ski jumper it is essential to know what aerodynamic forces are acting on the ski jumper. However, few data on this are available, especially for a V-style ski jumping flight. We have measured the aerodynamic forces during the free flight phase for a V-style, as well as a parallel-style, ski jump by employing a full-size model in a wind tunnel. The aerodynamic force data, (drag, lift and pitching moment) were obtained to create an aerodynamic database. These forces are given in polynomial form as functions of the angle of attack, the body-ski (forward leaning) angle and the ski-opening (V-style) angle. Using the polynomial form database is a convenient way of obtaining the aerodynamic forces. Moreover, the wind tunnel was equipped with a ground effect plate to measure the aerodynamic forces during the landing phase. It was found that the difference between the lift with and without the ground effect plate increases with the ski-opening angle. The longitudinal stability in the pitching motion of a body-ski combination is also discussed on the basis of the pitching moment data. This indicates that a stable pitching oscillation of the body-ski combination may arise around an equilibrium point in the angle of attack, the trim angle of attack, during flight.     

从"李小鹏跳"看世界跳马比赛的创新与发展

从体操新规则实施前后跳马动作的对比,研究了“李小鹏跳”的发展与创新历程。结果表明：世界男子跳马今后的发展将是多度转体动作与多周空翻动作的较量,多度转体动作略有优势,各国运动员应根据各自特点选用不同类型的动作。     

不同形式跳深练习发展弹跳力的实证研究

跳深作为一种超等长练习形式,可有效发展肌肉的收缩速度与收缩能力,提高肌肉力量与弹跳力。本文通过实验法、文献资料法、数理统计法分析得出,不同跳深高度、跳深形式练习的选择对发展肌肉弹跳力不同,向上跳还是向前跳,单腿还是双腿,应依据运动竞赛项目的发力工作方式而定。     

煤矿主斜井皮带多电动机驱动功率分配探讨

对煤矿主斜井皮带三台电动机拖动系统和电动机功率分配不平衡问题,从电动机特性和机械传动两方面进行理论探讨,提出了调节功率平衡的方法。