原地摆臂纵跳和抱头纵跳动力学特征的比较

运用三维测力台(Kistler)和红外光点自动捕捉测试系统(Qualisys-MCU500)对北京体育大学男子排球队9名运动员分别进行了摆臂纵跳和抱头纵跳的测试,结果表明:摆臂纵跳蹬伸过程中最大力值大于抱头纵跳,但是由于蹬伸后半段时间的延长使后半段蹬伸力的梯度值没有明显增加;落地时地面最大冲击力与纵跳高度无关;摆臂纵跳的冲量值大于抱头纵跳,但研究结果发现纵跳高度与冲量并没有显著性相关关系.     

原地连续纵跳的运动生物力学特征研究

为研究原地连续纵跳的运动生物力学特征,运用录像拍摄与三维测力同步测试的方法对其研究发现,不同频率作用下的时间参数存在一定差异,随着纵跳频率的增加,时间参数都表现出逐渐减小的趋贽.同一频率作用下随着运动时间的延长,支撑时间逐渐增人.蹬伸力峰值随着连续纵跳运动时间的延长呈现明显逐渐减小的趋势,不同频率原地连续纵跳蹬伸力峰值对起跳效果的影响程度是不同的;缓冲冲量和蹬伸冲量随运动时间的延长,也都呈现出明显的逐渐减小的趋势,并且运动前期的恢复系数人于1.     

沙滩原地纵跳与硬地原地纵跳动力学机制的比较研究

运用三维测力台，对我国12名沙滩女子排球运动员进行了沙滩和硬地2种介质上原地起跳的动力学测试。结果表明，沙滩原地纵跳和硬地原地纵跳的起跳用力方式相同，但动力学机制存在显著性差异，这是沙滩训练弹跳力的重要动力学依据。     

不同快慢节奏对连续性原地纵跳影响的实验研究

采用录像和测力同步测试的方法，对10名受试者以80、120、160次，min3种不同节奏的连续性原地纵跳动作进行实验测试，结果表明：随着节奏的加快．支撑时间显著缩短；人体腾空的高度、质心下降与上升的最大速度等有显著性的下降；踝、膝、髋3个关节的屈曲程度，膝关节的伸屈角速度都有显著地下降；人体的刚度系数变大，弹性变小。     

运动性疲劳对纵跳动力学特征的影响

为揭示下肢运动性疲劳对纵跳的动力学特征的影响,22名男性体育教育专业大学生志愿参加了实验。结果表明,随着下肢负荷时间的增加纵跳的垂直方向分力和冲量下降,而左右、前后方向分力和冲量增加,三个方向的力矩随负荷时间的延长而增加。     

膝关节损伤对排球运动员急停纵跳的影响

目的:对辽宁省排球队女运动员下肢急停纵跳落地时的力矩和最大关节角度进行研究,以期对有膝关节损伤的排球运动员进行科学训练提供参考。方法:以14名辽宁省排球队女运动员为研究对象,将运动员分为两组,其中无伤组8人,损伤组6人,采用三维测力平台和红外光电运动捕捉系统,记录受试者在完成急停纵跳动作落地时的髋关节、膝关节、踝关节的力矩以及最大关节角度数据。结果:在急停纵跳落地时,损伤膝关节的旋转、收展力矩大于无伤组,屈伸力矩小于无伤组,损伤组的髋关节的屈伸、收展、旋转力矩均大于无伤组;损伤组的踝关节旋转力矩小于无伤组,收展力矩和屈伸力矩大于无伤组。损伤组的踝关节在屈伸、收展和旋转时的最大关节角度大于无伤组;损伤组的膝关节在屈伸和收展时的最大关节角度大于无伤组,旋转时小于无伤组;损伤的髋关节屈伸和收展时的最大关节角度大于无伤组,髋关节旋转时的最大关节角度左侧小于无伤组,右侧大于无伤组。结论:膝关节损伤的运动员完成急停纵跳动作落地时,通过代偿性改变增大髋关节力矩、增加膝关节旋转和收展力矩,增大踝关节收展和屈伸力矩,增加膝关节和髋关节在屈伸和收展时活动角度,增加膝关节屈伸和收展时活动角度来完成动作。     

男大学生部分身体形态指标和原地纵跳能力的相关性

采用实验法，按原地纵跳能力把受试者分为优秀组和一般组，研究不同组间受试者的身体形态指标和原地纵跳能力的相关性。结果发现：相对跟腱长和原地纵跳能力成反比，组间只有大腿围、小腿围和原地纵跳能力有显著性差异。表明：跟腱相对较短而腓肠肌相对较长者，有更好的原地纵跳能力；跟腱长Ⅱ相对长反映原地纵跳能力可能更合适；初级选材用形态学指标推断运动能力，可能只在特定的年龄、人群中适用，同时还要考虑运动训练对运动能力的影响。     

不同弹跳能力的3名运动员其原地纵跳的运动生物力学指标的比较

根据力学原理,本文建立了不同运动员间进行原地纵跳运动生物力学指标同步比较的方法。三名不同弹跳能力的运动员其原地纵跳进行了测力与录相同步分析。研究表明,能力强者在技术上表现出髋、膝、踝关节处极强的协调发力能力,而能力差者均出现滞后或超前的不协调性发力;不同能力的运动员在膝关节处发力较为接近,肩关节均是提前发力。但能力强者具有较强的肩关节发力能力,能力最差者则在肩、踝等关节处发力能力明显不足。     

负荷时间长短对纵跳能力影响的动力学研究

分析受试者在功率自行车上不同运动负荷时间后纵跳的动力学特征变化规律 ,研究结论 :①大强度持续运动约 3min左右 ,纵跳的爆发力、平均功率、平均力值等动力学指标显著上升 ;运动 5min后 ,上述指标的变化情况正好相反 ;②只有在适宜的运动负荷时间后 ,纵跳的动力学特征才进入有利于运动能力发挥的较好的组合状态     

1次力竭性运动前后纵跳某些动力学特征的研究

对12名男性受试者1次力竭性功率自行车运动前后纵跳的某些动力学特征测定,发现力竭性运动后纵跳的垂直方向的分力、冲量值下降(P<0.05);而水平方向的分力、冲量值增加(P<0.05)。     

Acute kinematic and kinetic adaptations to wearable resistance during vertical jumping

One variation of vertical jump (VJ) training is resisted or weighted jump training, where wearable resistance (WR) enables jumping to be overloaded in a movement specific manner. A two-way analysis of variance with Bonferroni post hoc contrasts was used to determine the acute changes in VJ performance with differing load magnitudes and load placements. Kinematic and kinetic data were quantified using a force plate and contact mat. Twenty sport active subjects (age: 27.8?±?3.8 years; body mass (BM): 70.2?±?12.2?kg; height: 1.74?±?0.78?m) volunteered to participate in the study. Subjects performed the counter movement jump (CMJ), drop jump (DJ) and pogo jump (PJ) wearing no resistance, 3% or 6% BM affixed to the upper or lower body. The main finding in terms of the landing phase was that the effect of WR was non-significant (P?>?.05) on peak ground reaction force. With regard to the propulsive phase the main findings were that for both the CMJ and DJ, WR resulted in a significant (P?<?.05) decrease in jump height (CMJ: ?12% to ?17%, DJ: ?10% to ?14%); relative peak power (CMJ: ?8% to ?17%, DJ: ?7% to ?10%); and peak velocity (CMJ: ?4% to ?7%, DJ: ?3% to ?8%); while PJ reactive strength index was significantly reduced (?15% to ?21%) with all WR conditions. Consideration should be given to the inclusion of WR in sports where VJ’s are important components as it may provide a novel movement specific training stimulus.

Highlights

• WR of 3 or 6 % BM provided a means to overload the subjects in this study resulting in decreased propulsive power and velocity that lead to a reduced jump height and landing force.

• Specific strength exercises that closely mimic sporting performance are more likely to optimise transference, therefore WR with light loads of 3–6% body mass (BM)appear a suitable tool for movement specific overload training and maximising transference to sporting performance.

• Practitioners can safely load their athletes with upper or lower body WR of 3–6% BM without fear of overloading the athletesover and above the landing forces they are typically accustomed too.

• As a training stimulus it would seem the WR loading provides adequate overload and athletes should focus on velocity of movement to improve power output and jump height i.e. take-off velocity.

     

Temporal and kinetic analysis of unilateral jumping in the vertical,horizontal, and lateral directions

Abstract

The aims of this study were to: (1) assess the reliability of various kinetic and temporal variables for unilateral vertical, horizontal, and lateral countermovement jumps; (2) determine whether there are differences in vertical ground reaction force production between the three types of jumps; (3) quantify the magnitude of asymmetry between limbs for variables that were established as reliable in a healthy population and whether asymmetries were consistent across jumps of different direction; and (4) establish the best kinetic predictor(s) of jump performance in the vertical, horizontal, and lateral planes of motion. Thirty team sport athletes performed three trials of the various countermovement jumps on both legs on two separate occasions. Eccentric and concentric peak force and concentric peak power were the only variables with acceptable reliability (coefficient of variation = 3.3–15.1%; intra-class correlation coefficient = 0.70–0.96). Eccentric and concentric peak vertical ground reaction force (14–16%) and concentric peak power (45–51%) were significantly (P < 0.01) greater in the vertical countermovement jump than in the horizontal countermovement jump and lateral countermovement jump, but no significant difference was found between the latter two jumps. No significant leg asymmetries (–2.1% to 9.3%) were found in any of the kinetic variables but significant differences were observed in jump height and distance. The best single predictors of vertical countermovement jump, horizontal countermovement jump, and lateral countermovement jump performance were concentric peak vertical power/body weight (79%), horizontal concentric peak power/body weight (42.6%), and eccentric peak vertical ground reaction force/body weight (14.9%) respectively. These findings are discussed in relation to monitoring and developing direction-specific jump performance.     

Influence of lumbar spine extension on vertical jump height during maximal squat jumping

Abstract

The purpose of this study was to determine the influence of lumbar spine extension and erector spinae muscle activation on vertical jump height during maximal squat jumping. Eight male athletes performed maximal squat jumps. Electromyograms of the erector spinae were recorded during these jumps. A simulation model of the musculoskeletal system was used to simulate maximal squat jumping with and without spine extension. The effect on vertical jump height of changing erector spinae strength was also tested through the simulated jumps. Concerning the participant jumps, the kinematics indicated a spine extension and erector spinae activation. Concerning the simulated jumps, vertical jump height was about 5.4 cm lower during squat jump without trunk extension compared to squat jump_. These results were explained by greater total muscle work during squat jump, more especially by the erector spinae work (+119.5 J). The erector spinae may contribute to spine extension during maximal squat jumping. The simulated jumps confirmed this hypothesis showing that vertical jumping was decreased if this muscle was not taken into consideration in the model. Therefore it is concluded that the erector spinae should be considered as a trunk extensor, which enables to enhance total muscle work and consequently vertical jump height.     

Effect of 6-weeks WBVT on the behaviour of the lower limb muscle fibres during vertical jumping

The purpose of the current study was to examine the effect of 6 weeks of whole body vibration training (WBVT) on body composition, muscle activity of the gastrocnemius and vastus lateralis, gastrocnemius muscle architecture (static and dynamic) and ground reaction forces (performance jump) during the take-off phase of a countermovement jump in young healthy adult males. A total of 33 men (23.31 ± 5.62 years) were randomly assigned to a whole body vibration group (experimental group, EG_WBVT: n = 17; 22.11 ± 4.97 years) or a control group (CG: n = 16; 24.5 ± 6.27 years). The total duration of the intervention phase (WBVT) was 6 weeks with a frequency of 3 sessions per week. Statistically significant differences were observed (P ≤ 0.05) between pre- and post-test in the power peak (Δ 1.91 W · kg^?1; P = 0.001), take-off velocity (0.1 cm · s^?1; P = 0.002) and jump height (Δ 0.4 cm; P = 0.002) for EG_WBVT. There were no statistically significant differences in any of the body composition and muscle architecture variables. Moreover, no significant differences were found between EG_WBVT and CG nor changes in muscle activity during take-off phase of the gastrocnemius and vastus lateralis pre- versus post-training. This study suggests that a 6-week WBVT programme with increasing intensity improves jump performance but does not alter muscle activity nor muscle architecture in healthy young men.     

Sex and acute weighted vest differences in force production and joint work during countermovement vertical jumping

It is unclear whether weighted vest (WV) use improves countermovement vertical jump (CMVJ) performance by enhancing stretch-shortening cycle (SSC) function via increased storage and utilisation of elastic strain energy. In is also unknown whether WV use stimulates different responses in men and women. WV effects on energy storage and utilisation during CMVJ were examined in men and women. Nine men (25 ± 3 y; 89.7 ± 18.7 kg; 1.8 ± 0.1 m) and 12 women (24 ± 3 y; 62.7 ± 10.3 kg; 1.6 ± 0.1 m) performed CMVJ wearing a WV with (loaded) and without (unloaded) 10% added mass while kinematic and ground reaction force (GRF) data were obtained. A longer eccentric sub-phase and increased storage of elastic strain energy occurred when loaded. Increased positive joint work occurred during the concentric portion of loaded CMVJ. Women exhibited less positive hip work and greater positive ankle work than men during the unloading and eccentric sub-phases, respectively. Joint work was similar between sexes during the concentric sub-phase, likely due to decreased trunk extension excursion in men when loaded. Women and men employ different SSC strategies during the CMVJ, though the different strategies do not alter energy storage or concentric mechanical output.     

Perceptions of change and certainty regarding the self-as-exerciser: a multistudy report

The purpose of these studies was to examine the relationship between perceptions of exercise-related changes (i.e., perceived mastery and physical change) and certainty with regard to the self-as-exerciser. It was hypothesized that seeing "change" would be associated with more favorable levels of exercise self-certainty and behavior relative to "no change." Online surveys were repeatedly administered across 4 months (Study 1) and 4 weeks (Study 2) to 196 university students (M(age) = 20.17), and 250 community dwellers (M(age) = 38.44), respectively. Data were analyzed via latent variable modeling procedures. Consistent with hypotheses, latent classes (i.e., subgroups) reflecting interindividual differences in levels and trajectories of perceived change were associated with distinct patterns of self-certainty and exercise behavior. The findings suggest that adults who experience mastery of skills and physiological changes also have greater self-certainty and exercise more regularly than those who do not see progress or feel as certain of their exercise identity.     

浅析跳台滑雪运动后继乏人的问题

就目前跳台滑雪存在的人才匮乏、发展受阻的情况,对梯队结构和场地设施的基本状况进行了调查,结果表明,基础训练薄弱、场地设施落后、普及面较小、选才难、训练方法落后和经费不足等问题比较突出.通过分析,提出了解决问题的几点建议.     

Segmental and kinetic contributions in vertical jumps performed with and without an arm swing

To determine the contributions of the motions of the body segments to the vertical ground reaction force (Fz), the joint torques produced by the leg muscles, and the time course of vertical velocity generation during a vertical jump, 15 men were videotaped performing countermovement vertical jumps from a force plate with and without an arm swing. Linear kinematic, Fz, and joint torque data were computed and compared using repeated measures analysis of variance. Maximum jump height was significantly larger in the arm swing jumps compared to the no arm swing jumps and was due to both a higher height of the center of mass (CM) at takeoff (54%) and a larger vertical velocity of the CM at takeoff (46%). The net vertical impulse created during the propulsive phase of the arm swing jumps was greater due to a trend of an increased duration (0.021 s) of the propulsive phase and not to larger average values of Fz. In the arm swing jumps, the arm motion resulted in the arms making a larger maximal contribution to Fz during the middle of the propulsive phase and decreased the negative contribution of the trunk-head and thigh to Fz late in the propulsive phase. Last, the arm swing decreased the extensor torques at the hip (13%), knee (10%), and ankle (10%) early in the propulsive phase but augmented these same extensor torques later in the propulsive phase.