Effect of strength and speed of torque development on balance recovery with the ankle strategy

In the event of an unexpected disturbance to balance, the ability to recover a stable upright stance should depend not only on the magnitude of torque that can be generated by contraction of muscles spanning the lower extremity joints but also on how quickly these torques can be developed. In the present study, we used a combination of experimental and mathematical models of balance recovery by sway (feet in place responses) to test this hypothesis. Twenty-three young subjects participated in experiments in which they were supported in an inclined standing position by a horizontal tether and instructed to recover balance by contracting only their ankle muscles. The maximum lean angle where they could recover balance without release of the tether (static recovery limit) averaged 14.9 +/- 1.4 degrees (mean +/- SD). The maximum initial lean angle where they could recover balance after the tether was unexpectedly released and the ankles were initially relaxed (dynamic recovery limit) averaged 5.9 +/- 1.1 degrees, or 60 +/- 11% smaller than the static recovery limit. Peak ankle torque did not differ significantly between the two conditions (and averaged 116 +/- 32 Nm), indicating the strong effect on recovery ability of latencies in the onset and subsequent rates of torque generation (which averaged 99 +/- 13 ms and 372 +/- 267 N. m/s, respectively). Additional experiments indicated that dynamic recovery limits increased 11 +/- 14% with increases in the baseline ankle torques prior to release (from an average value of 31 +/- 18 to 54 +/- 24 N. m). These trends are in agreement with predictions from a computer simulation based on an inverted pendulum model, which illustrate the specific combinations of baseline ankle torque, rate of torque generation, and peak ankle torque that are required to attain target recovery limits.     

排球运动起跳过程中踝关节的生物力学特性

文题释义： 急停起跳：在激烈的排球比赛中,急停起跳动作是运动员比赛过程中出色完成扣球、拦网、跳发球、跳传球等技术所必不可少的关键阶段,也是运动员获得较好起跳高度的关键实施环节。 踝关节的活动范围：研究发现长期从事举重项目的人比正常人的踝关节活动度要小,长期从事游泳项目的人比正常人的踝关节活动度要大。踝关节的活动范围往往还跟运动成绩相关联,如短跑、速滑等竞速性项目运动成绩好的运动员踝关节的活动度也相对较好。 背景：目前对踝关节的生物力学特性研究多集中于方法学的探讨,对复合动作模式下踝关节生物力学特征的研究较少。 目的：分析对排球运动员起跳落地时踝关节的运动学和动力学特性。 方法：研究选取天津体育学院排球专项运动的学生男女各20名。主要采用Vicon三维运动捕捉系统和Kistler三维测力台,同步采集受试者在起跳落地时踝关节运动学与动力学参数,总共获得3次有效数据,利用统计学方法对数据进行对比分析。研究方案的实施符合天津体育学院的相关伦理要求,所有受试者均为自愿参加,并对试验过程完全知情同意。 结果与结论：①发现在该动作模式中,踝关节跖屈角度男性明显小于女性,在起跳阶段踝关节处于内翻和内旋状态,在落地缓冲阶段踝关节处于内翻和外旋状态,且角度男性组略大于女性,此时极易造成踝关节损伤;②三维方向的峰力矩和力值男性组均大于女性;三维方向峰值力矩和力出现的时间男性组晚于女性,而且存在双腿力量不均衡以及双脚不同时着地情况。 ORCID: 0000-0003-4584-148X(鲍春雨) 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

羽毛球运动员足踝落地瞬间生物力学特征与运动风险分析

目的 探讨羽毛球运动员足踝落地瞬间生物力学特征对运动风险的影响，为避免初学者踝关节高频次、高强度触地发生运动风险提供参考。方法 采用三维测力台和动作捕捉系统，对30名羽毛球运动初学者（实验组）和30名高水平运动员（对照组）在进行蹬转（1步）起跳动作时踝关节落地瞬间的运动学与动力学数据进行采集。结果 实验组跖屈背屈角度均显著小于对照组，实验组内翻和内旋角度均显著大于对照组，外翻和外旋角度不存在显出差异。实验组向左右方向力均显著大于对照组，实验组与对照组前后方向力和垂直方向力不存在显著性差异。实验组外翻、外旋力矩均显著大于对照组，对照组内旋力矩显著高于实验组。结论 相比初学者，专业运动员踝关节运动具有良好的动态稳定性和灵活性，左右方向较小的活动幅度和受力就可以完成缓冲任务，并且专业运动员跖屈背屈角度增大，也是良好训练效果的体现，使缓冲时间稍微加长，以防止踝关节突然落地时刻的冲击。     

Neuromusculoskeletal torque-generation process has a large destabilizing effect on the control mechanism of quiet standing

The delay of the sensory-motor feedback loop is a destabilizing factor within the neural control mechanism of quiet standing. The purposes of this study were 1) to experimentally identify the neuromusculoskeletal torque-generation process during standing posture and 2) to investigate the effect of the delay induced by this system on the control mechanism of balance during quiet standing. Ten healthy adults participated in this study. The ankle torque, ankle angle, and electromyograms from the right lower leg muscles were measured. A ground-fixed support device was used to support the subject at his/her knees, without changing the natural ankle angle during quiet standing. Each subject was asked to mimic the ankle torque fluctuation by exerting voluntary ankle extension while keeping the supported standing posture. Using the rectified soleus electromyogram as the input and the ankle torque as the output, a critically damped, second-order system (twitch contraction time of 0.152 +/- 0.027 s) successfully described the dynamics of the torque-generation process. According to the performed Bode analysis, the phase delay induced by this torque-generation process in the frequency region of spontaneous body sway during quiet standing was considerably large, corresponding to an effective time delay of about 200 to 380 ms. We compared the stability of the balance control system with and without the torque-generation process and demonstrated that a much smaller number of gain combinations can stabilize the model with the torque-generation process than without it. We concluded that the phase delay induced by the torque-generation process is a more destabilizing factor in the control mechanism of quiet standing than previously assumed, which restricts the control strategies that can stabilize the entire system.     

Prophylactic ankle braces and knee varus-valgus and internal-external rotation torque

Context: Although prophylactic ankle bracing has been shown to be effective in reducing the incidence of ankle sprains,how these ankle braces might affect the other joints of the lower extremity is not clearly understood.Objective: To determine the effects of a prophylactic ankle brace on knee joint varus-valgus and internal-external rotation torque during a drop landing onto a slanted surface.Design: A repeated-measures design.Setting: Biomechanics research laboratory. Patients or Other Participants: Twenty-four physically active college students.Intervention(s): Participants were tested in a brace and no brace condition. Main Outcome Measure(s): We measured 3 dependent variables:(1) peak ankle inversion-eversion torque, (2) peak knee varus-valgus torque, and (3) peak knee internal-external rotation torque. A force plate was used to collect ground reaction force data, and 6 motion analysis cameras collected kinematic data during the unilateral drop landing. An adjustable bar was hung from the ceiling, and a slant board was positioned over the center of the force plate, so that the ankle of the participant's dominant leg would invert upon landing. Peak torque was measure din both the brace and no-brace conditions. The average of the peak values in 3 trials for both conditions was used for the statistical analysis.Results: Ankle eversion torque was significantly greater in the brace condition (F1,23 19.75, P < .01). Knee external rotation torque was significantly greater in the brace condition(F1,23 4.33, P <.05). Valgus knee torque was smaller in the brace condition, but the difference was not statistically significant(F1,23 3.45, P .08).Conclusions: This study provides an important first step in understanding the effects of prophylactic ankle bracing on other joints of the lower extremity. We found that prophylactic ankle bracing did have an effect on knee torque when the subject was landing on a slanted surface. Specifically, knee external rotation torque increased when the ankle was braced.     

腓骨支撑踝关节融合的三维有限元分析*☆

背景：利用有限元法进行模拟实验具有实验时间短、费用低、可模拟复杂边界条件、力学性能测试全面和可重复性好等优点。 目的：通过建立腓骨支撑固定融合踝关节三维有限元模型,分析其生物力学稳定性及安全性,并进一步探讨其生物力学特性。 方法：基于正常人体足踝部的三维CT断层数据集,重建踝关节几何形态,应用Abaqus6.9软件模拟踝关节4种活动模式(中立位、背屈位、内旋位和外旋位)时的受力状况,进行静力学有限元分析。 结果与结论：成功建立了腓骨支撑固定踝关节融合三维有限元模型,具有良好的几何相似性;在4种载荷下,背屈位引起的螺钉应力峰值最大,应力分布主要集中在螺钉的融合面水平,同时融合面发生的位移最大;而4枚螺钉中,胫骨后外侧螺钉应力最大;外侧支撑腓骨的应力主要集中在钉孔周围及上下钉孔之间的腓骨体部。说明踝关节行腓骨支撑固定融合时,应注意合理放置2枚交叉螺钉,避免应力过分集中,而内固定后应加强抗背屈方向的制动;在处理外侧支撑腓骨时,螺钉钉孔应避免靠近腓骨边缘且上下钉距不宜过大,可有效降低内固定失效的风险。 关键词：腓骨;踝关节;螺钉;融合;有限元;生物力学 doi:10.3969/j.issn.1673-8225.2012.13.004     

The development of balance control in children: comparisons of EMG and kinetic variables and chronological and developmental groupings

This cross-sectional study examined electromyographic (EMG) and kinetic variables during reactive balance responses in children grouped according to developmental level as compared with chronological age. Purposes were to explore relationships between the two types of variables and the effectiveness of the two grouping methods. Forty-four children between 9 months and 10 years old were tested for reactive balance control on a moveable platform. Surface electrodes measured EMG activity in the gastrocnemius (GA), hamstrings (HA), paraspinals (PS), tibialis anterior (TA), quadriceps (QA), and abdominal (AB) muscles. Timing and distance of center-of-pressure (COP) movements and peak muscle torques at the ankle, knee, and hip were also examined. Significant relationships and group differences were found between postural muscle activity and both the torque generated in the lower limbs and the timing and distance of COP adjustments employed to restabilize balance. As postural muscle activity increased and became more coordinated in timing, peak torque at the ankle and hip also increased, while the distance of and time to complete COP readjustments decreased. Children in younger/developmentally lower groups had smaller-magnitude and less-synergic muscle activity, lower peak torques, longer times to restabilize the COP, and greater COP paths than older/higher developmental groupings. Grouping by developmental level produced more statistical differences than did grouping by age. The correspondence of GA, HA, and PS muscle activity with COP measures and joint peak torques confirms that these muscles are key contributors to the balance synergy correcting for induced forward sway. Additionally, developmental level appears to be a much better predictor of balance improvement than chronological age.     

Direct measurement of human ankle stiffness during quiet standing: the intrinsic mechanical stiffness is insufficient for stability

During quiet standing the human 'inverted pendulum' sways irregularly. In previous work where subjects balanced a real inverted pendulum, we investigated what contribution the intrinsic mechanical ankle stiffness makes to achieve stability. Using the results of a plausible model, we suggested that intrinsic ankle stiffness is inadequate for providing stability. Here, using a piezo-electric translator we applied small, unobtrusive mechanical perturbations to the foot while the subject was standing freely. These short duration perturbations had a similar size and velocity to movements which occur naturally during quiet standing, and they produced no evidence of any stretch reflex response in soleus, or gastrocnemius. Direct measurement confirms our earlier conclusion; intrinsic ankle stiffness is not quite sufficient to stabilise the body or pendulum. On average the directly determined intrinsic stiffness is 91 ± 23 % (mean ± s.d. ) of that necessary to provide minimal stabilisation. The stiffness was substantially constant, increasing only slightly with ankle torque. This stiffness cannot be neurally regulated in quiet standing. Thus we attribute this stiffness to the foot, Achilles' tendon and aponeurosis rather than the activated calf muscle fibres. Our measurements suggest that the triceps surae muscles maintain balance via a spring-like element which is itself too compliant to guarantee stability. The implication is that the brain cannot set ankle stiffness and then ignore the control task because additional modulation of torque is required to maintain balance. We suggest that the triceps surae muscles maintain balance by predictively controlling the proximal offset of the spring-like element in a ballistic-like manner.     

Identification of ankle plantar-flexors dynamics in response to electrical stimulation

Modeling the muscle response to functional electrical stimulation (FES) is an essential step in the design of closed-loop controlled neuroprostheses. This study was aimed at identifying the dynamic response of ankle plantar-flexors to FES during quiet standing. Thirteen healthy subjects stood in a standing frame that locked the knee and hip joints. The ankle plantar-flexors were stimulated bilaterally through surface electrodes and the generated ankle torque was measured. The pulse amplitude was sinusoidally modulated at five different frequencies. The pulse amplitude and the measured ankle torque fitted by a sine function were considered as input and output, respectively. First-order and critically-damped second-order linear models were fitted to the experimental data. Both models fitted similarly well to the experimental data. The coefficient of variation of the time constant among subjects was smaller in the case of the second-order model compared to the first-order model (18.1% vs. 79.9%, p < 0.001). We concluded that the critically-damped second-order model more consistently described the relationship between isometric ankle torque and surface FES pulse amplitude, which was applied to the ankle plantar-flexors during quiet standing.     

外侧楔形鞋垫对足踝生物力学影响的有限元分析

目的 探究外侧楔形鞋垫对足踝内部组织(包括足骨、关节和韧带)的生物力学影响。 方法 建立并验证足踝-鞋垫-地面三维有限元模型,探究步态 3 个关键瞬间赤足模型和鞋垫干预模型的足底压力分布、关节接触压力、跖骨及主要韧带的应力。 结果 5°外侧楔形鞋垫模型足底峰值压力比赤足模型减小 65. 8% 。 鞋垫干预使楔舟关节处峰值接触压力减小;距下关节处峰值接触压力和第 4、5 跖骨处峰值应力增大。 结论 本研究量化评估了外侧楔形鞋垫对足踝各部分的生物力学影响,提出了可适当减小外侧楔形鞋垫第 4、5 跖骨处倾斜角度的设计建议。     

Development of a sliding mode control model for quiet upright stance

Human upright stance appears maintained or controlled intermittently, through some combination of passive and active ankle torques, respectively representing intrinsic and contractile contributions of the ankle musculature. Several intermittent postural control models have been proposed, though it has been challenging to accurately represent actual kinematics and kinetics and to separately estimate passive and active ankle torque components. Here, a simplified single-segment, 2D (sagittal plane) sliding mode control model was developed for application to track kinematics and kinetics during upright stance. The model was implemented and evaluated using previous experimental data consisting of whole body angular kinematics and ankle torques. Tracking errors for the whole-body center-of-mass (COM) angle and angular velocity, as well as ankle torque, were all within ∼10% of experimental values, though tracking performance for COM angular acceleration was substantially poorer. The model also enabled separate estimates of the contributions of passive and active ankle torques, with overall contributions estimated here to be 96% and 4% of the total ankle torque, respectively. Such a model may have future utility in understanding human postural control, though additional work is needed, such as expanding the model to multiple segments and to three dimensions.     

Biomechanical assessment with electromyography of post-stroke ankle plantar flexor spasticity

Spasticity has been defined as a motor disorder characterized by a velocity-dependent increase in tonic stretch reflex (muscle tone). Muscle tone consists of mechanical-elastic characteristics, reflex muscle contraction and other elements. The aims of this study were to determine whether to assess spasticity quantitatively, and to characterize biomechanical and electromyographic spasticity assessment parameters. These assessment parameters were described by investigating the correlation between clinical measures and the response to passive sinusoidal movement with consecutive velocity increments. Twenty post-stroke hemiplegic patients and twenty normal healthy volunteers were included in the study. Five consecutive sinusoidal passive movements of the ankle were performed at specific velocities (60, 120, 180, and 240 degrees/ sec). We recorded the peak torque, work, and threshold angle using a computerized isokinetic dynamometer, and simultaneously measured the rectified integrated electromyographic activity. We compared these parameters both between groups and between different velocities. The peak torque, threshold angle, work, and rectified integrated electromyographic activity were significantly higher in the post-stroke spastic group at all angular velocities than in the normal control group. The threshold angle and integrated electromyographic activity increased significantly and linearly as angular velocity increased, but the peak torque and work were not increased in the post-stroke spastic group. Peak torque, work, and threshold angle were significantly correlated to the Modified Ashworth scale, but the integrated electromyographic activity was not. The biomechanical and electromyographic approach may be useful to quantitatively assess spasticity. However, it may also be very important to consider the different characteristics of each biomechanical parameter.     

Finite element modeling of a 3D coupled foot-boot model

Increasingly, musculoskeletal models of the human body are used as powerful tools to study biological structures. The lower limb, and in particular the foot, is of interest because it is the primary physical interaction between the body and the environment during locomotion. The goal of this paper is to adopt the finite element (FE) modeling and analysis approaches to create a state-of-the-art 3D coupled foot–boot model for future studies on biomechanical investigation of stress injury mechanism, foot wear design and parachute landing fall simulation. In the modeling process, the foot–ankle model with lower leg was developed based on Computed Tomography (CT) images using ScanIP, Surfacer and ANSYS. Then, the boot was represented by assembling the FE models of upper, insole, midsole and outsole built based on the FE model of the foot–ankle, and finally the coupled foot–boot model was generated by putting together the models of the lower limb and boot. In this study, the FE model of foot and ankle was validated during balance standing. There was a good agreement in the overall patterns of predicted and measured plantar pressure distribution published in literature. The coupled foot–boot model will be fully validated in the subsequent works under both static and dynamic loading conditions for further studies on injuries investigation in military and sports, foot wear design and characteristics of parachute landing impact in military.     

Effects of five years of chronic STN stimulation on muscle strength and movement speed

This study examined the long-term effects of chronic subthalamic nucleus (STN) deep brain stimulation (DBS) using both clinical evaluation and laboratory motor control measures. Over a 5-year time period, changes in the motor section of the Unified Parkinson’s Disease Rating Scale (UPDRS) and movement speed and strength at the ankle joint were evaluated on and off STN DBS in eight patients with Parkinson’s disease (PD). Four patients were also studied at the elbow joint. Patients with PD originally received unilateral STN DBS between years 2001 and 2003. They were re-evaluated after 5 years of long-term STN DBS between years 2006–2008. At baseline (year 0) and after 5 years, patients with PD were tested off treatment and on STN DBS. In each testing condition, patients performed ballistic, single degree of freedom ankle dorsiflexion and ankle plantarflexion movements and peak velocity was calculated. Patients also performed maximal voluntary contractions at the ankle joint in both directions, and peak torque was calculated. Results showed increased motor UPDRS scores from year 0 to year 5, but STN DBS was efficacious in reducing them. In contrast to the increase in motor UPDRS scores, motor control results showed a marked improvement in peak velocity and peak torque over the 5-year time period in the off treatment condition, and STN DBS was efficacious by improving both peak velocity and peak torque. The current findings suggest that 5 years of chronic STN DBS can have beneficial effects on the motor system over the long term in discrete motor tasks in which maximal effort and maximal neural output is required.     

Multisensory control of human upright stance

The interaction of different orientation senses contributing to posture control is not well understood. We therefore performed experiments in which we measured the postural responses of normal subjects and vestibular loss patients during perturbation of their stance. Subjects stood on a motion platform with their eyes closed and auditory cues masked. The perturbing stimuli consisted of either platform tilts or external torque produced by force-controlled pull of the subjects' body on a stationary platform. Furthermore, we presented trials in which these two stimuli were applied when the platform was body-sway referenced (i.e., coupled 1:1 to body position, by which ankle joint proprioceptive feedback is essentially removed). We analyzed subjects' postural responses, i.e., the excursions of their center of mass (COM) and center of pressure (COP), using a systems analysis approach. We found gain and phase of the responses to vary as a function of stimulus frequency and in relation to the absence versus presence of vestibular and proprioceptive cues. In addition, gain depended on stimulus amplitude, reflecting a non-linearity in the control. The experimental results were compared to simulation results obtained from an 'inverted pendulum' model of posture control. In the model, sensor fusion mechanisms yield internal estimates of the external stimuli, i.e., of the external torque (pull), the platform tilt and gravity. These estimates are derived from three sensor systems: ankle proprioceptors, vestibular sensors and plantar pressure sensors (somatosensory graviceptors). They are fed as global set point signals into a local control loop of the ankle joints, which is based on proprioceptive negative feedback. This local loop stabilizes the body-on-foot support, while the set point signals upgrade the loop into a body-in-space control. Amplitude non-linearity was implemented in the model in the form of central threshold mechanisms. In model simulations that combined sensor fusion and thresholds, an automatic context-specific sensory re-weighting across stimulus conditions occurred. Model parameters were identified using an optimization procedure. Results suggested that in the sway-referenced condition normal subjects altered their postural strategy by strongly weighting feedback from plantar somatosensory force sensors. Taking this strategy change into account, the model's simulation results well paralleled all experimental results across all conditions tested.     

空心螺钉不同固定方式治疗后踝骨折的生物力学研究

目的 基于有限元方法研究空心螺钉不同角度固定对后踝骨折的生物力学影响,确定空心螺钉的最佳固定方式。方法 采用CT图像重建包含胫骨、腓骨、距骨以及相应软骨和韧带的踝关节有限元模型,在验证其有效性基础上建立1/2后踝骨折模型,分析空心螺钉不同固定方式对后踝骨折固定模型的生物力学影响。结果 与螺钉0°、5°、10°、20°固定相比,螺钉15°固定时模型位移最小。螺钉15°固定时,螺钉应力比螺钉5°、10°、20°固定模型小,比螺钉0°固定模型大。但螺钉0°固定时,踝关节接触应力峰值比正常踝关节接触应力峰值大得多,易造成创伤性骨关节炎。结论 空心螺钉治疗累及关节面不超过1/2的后踝骨折安全有效;螺钉以不同角度固定时,模型的位移和应力不同。螺钉固定角度为15°时生物力学稳定性最好,可用于指导临床手术。     

Postural feedback responses scale with biomechanical constraints in human standing

We tested whether human postural responses can be described in terms of feedback control gains, and whether these gains are scaled by the central nervous system to accommodate biomechanical constraints. A feedback control model can describe postural responses for a wide range of perturbations, but biomechanical constraints—such as on the torque that can be exerted on the ground—make a single set of feedback gains inappropriate for all perturbations. To observe how postural responses change with perturbation magnitude, we applied fast, backward perturbations of magnitudes 3–15 cm to 13 healthy young volunteers (4 men, 9 women, aged 20–32 years). We used a 3-segment, sagittal-plane biomechanical model and a linear state feedback controller to reproduce the observed postural responses. Optimization was used to identify the best-fit feedback control gains for each trial. Results showed that trajectories of joint angles and joint torques were scaled with perturbation magnitude. This scaling occurred gradually, rather than abruptly changing at magnitudes where biomechanical constraints became active. Feedback gains were found to fit reasonably well with data (R ²=0.92) and to be multivariate and heterogenic in character, meaning that the torque produced at any joint is generally a function of motions not only at the same joint, but other joints as well. Hip gains increased and ankle gains decreased nearly linearly with perturbation magnitude, in accordance with biomechanical limitations on ground reaction torque. These results indicate that postural adjustments can be described as a single feedback control scheme, with scalable heterogenic gains that are adjusted according to biomechanical constraints.     

Biomechanical study of tarsometatarsal joint fusion using finite element analysis

Complications of surgeries in foot and ankle bring patients with severe sufferings. Sufficient understanding of the internal biomechanical information such as stress distribution, contact pressure, and deformation is critical to estimate the effectiveness of surgical treatments and avoid complications. Foot and ankle is an intricate and synergetic system, and localized intervention may alter the functions to the adjacent components. The aim of this study was to estimate biomechanical effects of the TMT joint fusion using comprehensive finite element (FE) analysis. A foot and ankle model consists of 28 bones, 72 ligaments, and plantar fascia with soft tissues embracing all the segments. Kinematic information and ground reaction force during gait were obtained from motion analysis. Three gait instants namely the first peak, second peak and mid-stance were simulated in a normal foot and a foot with TMT joint fusion. It was found that contact pressure on plantar foot increased by 0.42%, 19% and 37%, respectively after TMT fusion compared with normal foot walking. Navico-cuneiform and fifth meta-cuboid joints sustained 27% and 40% increase in contact pressure at second peak, implying potential risk of joint problems such as arthritis. Von Mises stress in the second metatarsal bone increased by 22% at midstance, making it susceptible to stress fracture. This study provides biomechanical information for understanding the possible consequences of TMT joint fusion.     

优秀青少年男子篮球运动员腰腹屈伸肌群生物力学特征

背景：目前,等速测试系统在评定各专项运动员肌肉功能的应用越来越受到重视,但运用等速肌力测试技术研究优秀青少年男子篮球运动员腰腹肌力特征的报道较少。 目的：研究优秀青少年男子篮球运动员腰腹屈伸肌群生物力学特征,为篮球项目的腰腹力量训练、科学选材和预防腰腹损伤提供依据。 方法：采用Cybex-Norm等速肌力测试系统,对广州男子篮球队运动员18人测定腰腹屈伸肌群在慢速60(°)/s和快速180(°)/s的肌力和做功情况。 结果与结论：受试者腰腹屈伸肌群的峰力矩和相对峰力矩在同一测试速度下,伸肌群大于屈肌群(P < 0.01);腰腹屈伸肌群的峰力矩、相对峰力矩、总功均随着测试速度的增加呈减小趋势(P < 0.05),伸肌群的峰力矩和相对峰力矩减少更显著(P < 0.01);腰腹屈伸肌群的相对功率随着测试速度的增加而呈上升趋势(P < 0.01);外线球员腰腹屈伸肌群各测试指标成绩优于内线球员;在等速向心收缩时,随测试速度加快,腰腹屈伸肌群的峰力矩屈伸比呈递减趋势,躯干稳定性减弱。结果提示,优秀青少年男子篮球运动员腰腹伸肌群肌力大于屈肌群;外线球员腰腹屈伸肌群的肌力优于内线球员;等速快速运动时,腰腹屈伸肌群力量减小,腰腹关节屈伸肌力平衡性减弱,应加强青少年男子篮球运动员腰腹核心肌群快速力量训练。   中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

护踝对功能性踝关节不稳患者下肢运动生物力学特征的影响

目的 探究护踝对功能性踝关节不稳(functional ankle instability,FAI)患者的保护作用,为其护踝的选择提供依据。 方法 15 名 FAI 患者随机佩戴半刚性、弹性护踝及无护踝以自选速度步行和跑步,运用红外光点运动捕捉系统和三维测力台采集其下肢运动生物力学参数。 通过 3×2 重复设计的双因素方差分析检验护踝和运动模式对下肢运动学、动力学和能量吸收的影响。 结果 护踝与运动模式对本研究中所有指标均无交互作用(P>0. 05)。不论运动模式,与无护踝相比,弹性护踝显著减少了 FAI 患者踝关节内翻角峰值、内翻角速度和踝关节能量吸收(P<0. 05),同时增加了踝关节外翻力矩( P < 0. 001);而半刚性护踝增加了踝关节内翻角峰值和内翻角速度(P<0. 05)。 此外,弹性护踝可降低着地时刻的膝关节内旋力矩和外旋力矩峰值(P<0. 05)。 结论 与无护踝相比,弹性护踝通过减小踝关节内翻角、内翻角速度和能量吸收,增大踝关节外翻力矩,继而起到预防踝关节扭伤的作用。 FAI 患者佩戴半刚性护踝后需定时关注踝关节慢性损伤风险。 整体来看,弹性护踝的防护效果可能更有效,且未引起膝关节功能补偿,可作为预防 FAI 患者踝关节扭伤的有效措施。