太极拳转体动作中下肢关节活动顺序性和肌肉力表现及肌肉激活特征

目的 分析太极拳转体与弓步动作中下肢关节活动顺序性、肌肉力表现和肌肉激活程度的差异,揭示太极拳转体动作的特征。 方法 募集 20 名练习时长超过 3 年的健康太极拳练习者,采用三维运动捕捉系统、测力台和表面肌电同步采集转体与弓步两种动作运动学、动力学和肌肉激活信息,并通过 OpenSim 仿真软件获取下肢肌力。结果 与弓步相比,转体动作髋、踝关节外旋幅度显著增大;膝关节外展和外旋力矩显著增大,股二头肌、半腱肌和内外侧腓肠肌峰值肌力显著增强,股二头肌、内外侧腓肠肌峰值肌力时刻显著提前,而股内外侧肌和胫骨前肌峰值肌力显著减小,胫骨前肌肌力最早达到峰值;股二头肌、股内外侧肌和内侧腓肠肌的平均激活水平和激活时间显著增加。 结论 太极拳转体动作由踝、髋关节依次转动组成,肌肉力表现的独特性在于重心两次转移致使支撑腿内外侧肌力曲线呈双峰型,因为全足着地延迟方式引发了腓肠肌与股四头肌激活顺序和肌肉平均激活水平改变。研究结果提示全足着地延迟方式具有调节肌肉激活顺序的作用,合理利用有助于提升临床康复效果。     

基于AnyBody仿真的太极拳不同步型特征

目的 对比太极拳初学者和专业者不同步型的下肢运动学、动力学、肌肉力参数差异,为太极拳科学化及制定运动处方提供依据。方法 以练习时长超过3年的30名太极拳练习者为专业组,30名无太极拳经历初学者作为对照组。用BTS红外捕捉系统、Kistler三维测力台采集太极拳动作数据,以AnyBody 7.0建模仿真系统计算运动学、动力学、肌力参数。结果 专业组独立步膝关节屈伸角度、膝关节X轴受力明显大于对照组（P＜0.01）。弓步、虚步、开立步、马步、仆步、独立步中,专业组下肢肌力均为大于对照组。专业组马步半膜肌、半腱肌、股二头肌肌力大于对照组（P＜0.05）,专业组仆步臀大肌、臀中肌、臀小肌、阔筋膜张肌、股外侧肌、股二头肌肌力大于对照组（P＜0.05）,独立步股外侧肌、股内侧肌、股二头肌、胫骨前肌肌力大于对照组（P＜0.05）。结论 太极拳练习时,膝关节为主要发力关节,专业者下肢用力明显大于初学者。独立步对髋关节影响较大,弓步、仆步对膝关节影响较大。不同水平太极拳练习者对下肢肌肉的激活程度不同,初学者练习时要针对不同动作影响刺激的肌肉,有针对性地区分练习,进而促进下肢肌肉协同用力。     

搂膝拗步膝踝关节预激活与共收缩的表面肌电分析

目的 分析长期太极拳练习者进行搂膝拗步和正常行走时下肢膝、踝关节肌群预激活与共收缩的表面肌电（surface electromyography, sEMG）特征,探讨太极预防跌倒的神经肌肉控制策略。方法 采用Vicon运动捕捉系统、Kistler测力板和Noraxon表面肌电图系统同步采集搂膝拗步和正常行走时股直肌、股二头肌、胫骨前肌、外侧腓肠肌的sEMG信号和体位信息。通过股直肌和股二头肌、胫骨前肌和外侧腓肠肌两对肌肉的积分肌电分别计算膝、踝关节预激活和共收缩。结果 与正常行走相比,搂膝拗步在4个阶段的平均用时显著增加;搂膝拗步在4个阶段内时间百分比存在显著性差异;搂膝拗步膝关节共收缩水平和预激活水平降低,踝关节共收缩水平和预激活水平升高。结论 长期的太极拳练习可能使膝关节周围肌肉的激活水平提高,增强肌肉群之间的协同作用,以帮助稳定关节。研究结果为神经肌肉控制障碍疾病的康复评估和训练提供参考。     

亚洲蹲和西方蹲的下肢关节运动学和肌肉激活比较

目的分析比较亚洲蹲和西方蹲动作中下肢关节运动学和肌肉激活程度的差异。方法以11名健康成年人为研究对象,采用三维运动捕捉系统、测力台和表面肌电同步采集两种下蹲动作的运动学、动力学和肌肉激活信息,并通过OpenSim计算下肢肌力。结果在膝关节弯曲角度峰值时刻,亚洲蹲骨盆前倾,而西方蹲骨盆后倾;此外,与亚洲蹲相比,西方蹲具有显著较小的髋关节屈角、较大的膝关节屈角、较大的髋关节外展角和内旋角。在自重深蹲的下降期和上升期中,西方蹲的比目鱼肌力峰值均显著大于亚洲蹲,西方蹲的胫骨前肌力均显著小于亚洲蹲,峰值时刻未见统计学差异。结论在亚洲蹲中,胫骨前肌激活和近侧端关节前屈可能有利于稳定;而在脚跟抬起的西方蹲中,比目鱼肌激活显著,但两者近端肌肉激活模式相同。研究结果为临床深蹲康复方案制定或深蹲训练方式的选择提供理论指导。     

痉挛型脑瘫儿童手术后表面肌电信号和关节角度评估

目的 通过表面肌电(surface electromyography, sEMG)和关节角度评估脑瘫儿童手术后运动功能。方法 采集16名痉挛型脑瘫患儿手术前后直线行走时股直肌、股二头肌、半腱肌、胫骨前肌、腓肠肌内外侧sEMG和髋、膝、踝关节角度,计算各步态时期sEMG均方根、积分肌电值和关节角度均值,进行肌力肌张力评估。结果 手术后,患儿下肢肌肉肌张力均显著降低(P<0.05),股直肌和股二头肌在摆动阶段肌力减小。胫骨前肌在摆动中末期肌力增大(P<0.05)。髋、膝关节屈曲角降低(P<0.05)。踝关节背屈角增大(P<0.05),内翻角减小(P<0.05)。结论 治疗后患者蹲伏步态和马蹄内翻足均得到改善,运动功能得到提升。sEMG结合关节角度分析可对患者肌肉功能进行定量评估,为临床诊断提供参考。     

太极拳白鹤亮翅对下肢肌电活动的影响

目的通过对比太极拳初学者和太极拳运动员白鹤亮翅动作关节角度活动变化、压力中心(center of pres-sure,COP)变化和肌肉活动特点,分析运动员是如何通过肌肉活动控制其白鹤亮翅的姿势平衡。方法太极拳运动员和初学者分两组各10人。记录太极白鹤亮翅动作时双下肢10块骨骼肌表面肌电图、双下肢3大关节的二维角运动和COP在侧方和前后的移位。每次试验8 s完成,重复5次。统计处理后,做肌电运动和平衡分析;其中肌电数据做标准化处理,并比较太极拳运动员和初学者的异同。结果运动员组支撑腿胫骨前肌、股二头肌、臀中肌)的肌电活动表现为显著高于初学者同侧腿骨骼肌的肌电活动;运动员组虚步腿的腓肠肌和股直肌的肌电活动显著高于初学组同侧同名肌。运动员组下肢3大关节最大平均活动角度比初学组大,支撑腿髋关节显著高于初学组同侧同关节。运动员组COP前后方向位移显著小于初学组。结论运动员可以通过肌肉活动的增强对抗COP的移位,保持姿势平衡稳定,而初学者COP前后移位失控时并没表现出积极的肌肉活动。初步解释了太极拳练习能提高人体下肢肌肉力量和平衡控制能力的原因。     

冲击载荷作用下运动员下肢动态响应的逆向动力学仿真

目的分析冲击载荷作用下羽毛球运动员下肢关节肌肉的动态响应变化。方法基于Any Body Modeling System软件建立人体肌骨模型,采用实测表面肌电信号进行验证,以运动捕捉系统和测力台测量数据进行模型驱动,对羽毛球右前场蹬跨步上网过程中下肢肌肉肌力、关节力和关节力矩进行逆向动力学仿真与分析。结果所建人体下肢肌骨模型经肌电信号验证有效。羽毛球蹬跨步上网过程中,髋、踝关节Z方向内力峰值显著高于X和Y方向内力峰值,而膝关节X方向内力峰值显著高于Y和Z方向内力峰值;缓冲期,髋关节X、Y、Z方向依次表现为内收力矩、伸髋力矩和内旋力矩,膝关节X、Y、Z方向依次表现为外展力矩、屈膝力矩、外旋力矩,踝关节X、Y方向依次表现为内翻力矩、跖屈力矩,且髋、膝、踝关节X方向力矩峰值显著高于Y和Z方向;股外侧肌、股二头肌、胫骨前肌、腓肠肌内侧在对抗地面冲击载荷时的肌力发挥较大,股直肌、半膜肌、比目鱼肌发挥的作用相对较小。结论建立的下肢肌骨模型可为冲击载荷作用下运动员下肢生物力学特性分析提供技术平台。为避免运动损伤,类似羽毛球前场蹬跨步上网冲击动作中尤其要重视触地瞬间地面反作用力载荷对髋、膝、踝关节前后及内外侧方向生物力学性质的影响,同时在对羽毛球运动员进行专项训练时切勿忽视对股外侧肌、股二头肌、胫骨前肌的专项力量发展。     

下肢姿势肌的肌电,特别论及腓肠肌

本文以Ediswan脑电墨水描记仪,肌内电极,观察了15例健康青年男子在不同姿势和运动时的下肢姿势肌——股四头肌、股二头肌、半腱肌、腓肠肌及比目鱼肌的电位活动。分析的初步结果是:一、腓肠肌对膝关节的作用1.在下肢支撑体重时:如立正站立时的电位表明腓肠肌拉大腿下端向后,协同股二头肌及半腱肌对抗股四头肌以强固膝关节。在下蹲时膝关节屈曲和起立时膝关节伸展的运动中,腓肠肌都出现了电位活动。在站立位身体前倾时,腓肠肌与比目鱼肌亦都出现了明显的电位活动。腓肠肌内侧头和外侧头在小腿内旋和外旋时皆有电位活动。2.在站立时一个下肢支撑体重:另一个下肢和地面垂直,慢屈及伸小腿时以及在坐位,大腿和地面平行慢伸和屈小腿时,腓肠肌都未出现电位活动。二、腓肠肌对踝关节的作用腓肠肌协同比目鱼肌蹠屈足,当走步支撑腿后蹬及站立位时它可提足跟向上。在直立姿势中,腓肠肌和比目鱼肌都参加强固踝关节,并调节小腿在足骨上的位置关系。三、我们对于股四头肌、股二头肌及半腱肌在膝关节所起的作用上亦做了电位观察。     

脑卒中患者步态启动时早期姿势调节阶段时间和强度参数特点

背景：早期姿势调节为即将执行的动作或面临的姿势干扰做出准备，从而有助于更好地执行动作以及减少干扰对姿势造成的不稳定影响。目的：探索不同平衡能力的脑卒中患者在以舒适速度启动步行时下肢关键肌在早期姿势调节阶段的时间和强度参数特点。方法：观察16例脑卒中恢复期患者早期姿势调节特点，根据有无跌倒史及Berg平衡量表得分分为无跌倒组8例和跌倒组8例。使用Noraxon惯性传感器、Noraxon Ultium EMG无线表面肌电仪采集步态启动过程中患者身体运动学数据和表面肌电数据。分析早期姿势调节阶段下肢胫骨前肌、腓肠肌内外侧、股直肌、股外侧肌和股二头肌6块关键肌的肌肉激活时间和激活顺序，以及步态启动前4个时间窗(各150 ms)的标准化的肌电积分值。结果与结论：(1)有跌倒史的患者在步态启动时，下肢6块关键肌的肌肉激活时间均早于无跌倒组，胫骨前肌、腓肠肌外侧头和股外侧肌的激活时间显著早于无跌倒组(P <0.01,P <0.05)；无跌倒组的肌肉激活顺序呈现出了比较规律的先激活伸肌后激活屈肌、大腿部肌肉激活早于小腿肌肉激活的特点；而跌倒组小腿部伸肌的激活要早于大腿部伸肌的激活，股外侧肌...     

人体膝关节股胫关节运动特性分析

目的　分析人体正常膝关节和人工膝关节高屈曲活动下股胫关节的运动,为膝关节运动特性研究、假体设计提供参考。 方法　选取健康志愿者,利用CT和MRI扫描数据建立正常全膝关节三维有限元模型以及TKA术后有限元模型,采取三束股四头肌肌力非同步变力加载,模拟人体下蹲运动,以分析股胫关节的相对运动特性,并检索相关研究结果以便对比分析。 结果　获得正常膝关节以及TKA术后人体下蹲过程中股骨相对胫骨的三维相对运动数据,结果表明,TKA术前、后股胫关节相对运动的总体趋势相近,同时在前后位移、远近位移、内外位移、内收外展和内外旋等最大值方面存在差异;同时通过对比分析TKA前后股胫关节相对运动以及相关文献数据,发现结果存在不同程度差异。 结论　究其原因,正常膝关节相对运动差异主要在于股胫关节各个运动方向上和不同屈曲度时约束程度的改变;人工膝关节相对运动差异主要来源于膝关节型面和结构的改变;同时与坐标系的定义、在体和离体的差异、负荷加载的差异相关。本研究针对人体正常膝关节和TKA术后膝关节股胫关节运动进行有限元仿真分析,对膝关节运动特性研究具有一定的参考价值。     

Gait modification with subject-specific foot progression angle in people with moderate knee osteoarthritis: Investigation of knee adduction moment and muscle activity

BackgroundSubject-specific foot progression angle (SSFPA) as a personalized gait modification is a novel approach to specifically reducing knee adduction.ObjectiveThis study aimed to investigate the effect of gait modification with SSFPA on the knee adduction moment and muscle activity in people with moderate knee osteoarthritis (KOA).MethodsIn this clinical trial, nineteen volunteers with moderate KOA were instructed to walk in four different foot progression angle conditions (5° toe-out, 10° toe-out, 5° toe-in, and 10° toe-in) to determine SSFPA that caused the greatest reduction in the greater peak of the knee adduction moment (PKAM). Immediately and after 30 minutes of gait modification with SSFPA, peak root means square (PRMS) and medial and lateral co-contraction index (CCI) were evaluated in the knee muscles.ResultWalking with 10° toe-in showed the most reduction in the greater PKAM (17.52 ± 15.39%) compared to 5° toe-in (7.1 ± 19.14%), 10° toe-out (1.26 ± 23.13%), and 5° toe-out (7.64 ± 16.71%). As the immediate effect, walking with SSFPA caused a 20.71 ± 12.07% reduction in the greater PKAM than the basic FPA (p < 0.001). After 30 minutes of gait retraining, the greater PKAM decreased by 10.36 ± 26.24%, but this reduction was not significant (p = 0.17). In addition, PRMS of lateral gastrocnemius increased (p = 0.04), and lateral CCI increased 10.72% during late stance (p = 0.04).ConclusionOur findings suggest the immediate effect of gait modification with SSFPA on decreasing the knee adduction moment. After gait retraining with SSFPA, the increase of lateral muscle co-contraction may enhance lateral knee muscle co-activity to unload the medial knee compartment.Clinical Trial Register Number: IRCT20101017004952N8.     

老年人搂膝拗步动作的下肢运动协调特征分析

目的 探讨65岁以上健康老年人进行太极拳搂膝拗步动作时下肢运动的协调性和稳定性。方法 30名太极拳练习者随机完成步行和搂膝拗步动作,采用Vicon三维动作捕捉系统收集下肢运动学数据。结果 搂膝拗步动作时,矢状面关节角度和髋-膝和膝-踝关节相位值变换频繁,髋-膝和膝-踝关节的平均相对相角绝对值以及髋、膝关节平均标准差显著小于步行。结论 与步行相比,太极拳搂膝拗步动作时髋-膝和膝-踝关节呈现出更协调稳定的关节间运动模式。太极拳锻炼可能会为老年人提供一种特定的协调训练方式,提高姿势稳定性,预防跌倒发生。     

Motor unit recruitment in human medial gastrocnemius muscle during combined knee flexion and plantarflexion isometric contractions

Previous work on multifunctional muscle has suggested that motor unit recruitment during a combined force task is the result of an interactive effect of weighted inputs acting simultaneously on the motoneuron pool. The present study shows that a similar effect describes motor unit activation in a two-joint muscle as forces are combined at both proximal and distal attachments. The recruitment thresholds of single motor units in medial gastrocnemius muscle were determined during combined knee flexion and plantarflexion isometric contractions. Slow isometric ramp contractions in knee flexion were produced while maintaining various background levels of plantarflexion force. The combination of knee flexion and plantarflexion forces at which a motor unit initially discharged was used to characterize recruitment as represented by the slope of the regression line fit to the individual data points. Each subject completed two experiments; one at each of two knee joint angles, with the ankle joint fixed at 90°. The effect of knee angle was assessed by comparing the slopes of the regression lines that characterized motor unit recruitment at each knee angle. Motor units in medial gastrocnemius were recruited when the linear sum of the forces exerted in plantarflexion and knee flexion exceeded a certain threshold of combined force. Specifically, the apparent force threshold of recruitment in knee flexion decreased as the level of force maintained in plantarflexion increased. Further, evidence is provided indicating that the linear relationship describing recruitment in two-joint muscle is dependent upon joint angle. The basis for the alteration in force threshold is thought to be related to changes in muscle length and mechanical advantage which might adjust the relative weighting of inputs that determine muscle activation patterns. These results indicate a possible common strategy employed by the nervous system in coordinating the activation of motor units to perform a specific task.     

A mathematical modelling study investigating the influence of knee joint flexion angle and extension moment on patellofemoral joint reaction force and stress

BackgroundPatellofemoral pain (PFP) is the most common orthopaedic condition among runners. Individuals with PFP exhibit greater patellofemoral joint (PFJ) reaction force and stress when compared with pain-free controls. However, it is not clear whether PFJ reaction force and stress are the highest (or lowest) when knee joint flexion angle and extension moment are in which combinations. We aimed to investigate the influence of knee joint flexion angle and extension moment on PFJ reaction force and stress.MethodsA PFJ sagittal model was used to quantify PFJ reaction force and stress. Based on the public dataset of the previous study, peak knee joint flexion angle and extension moment at various running speeds was calculated. Based on the calculated peak value, simulation ranges were set to knee joint flexion angle of 10–45° and extension moment of 0–240 Nm. The quadriceps force, effective lever arm length at quadriceps muscle, and PFJ contact area were determined as a function of the knee joint flexion angle and extension moment, and finally PFJ forces and stress were estimated.ResultsPFJ reaction force increased as the knee flexion angle and extension moment increased. Although PFJ stress also increased as the knee extension moment increased, it was at the highest and lowest at 10° and about 30° knee joint flexion angles, respectively.ConclusionsIncorporating knee flexion posture (approximately 30°) during running may help in reducing PFJ stress, which would be useful in the prevention of pain and act as an optimal treatment program for PFP.     

Knee rotation associated with dynamic knee valgus and toe direction

BackgroundDynamic knee valgus contributes to injuries of the anterior cruciate ligament (ACL). However, it is unclear how the knee rotates during dynamic knee valgus. Knee rotation significantly affects ACL strain. To understand knee rotation during dynamic knee valgus should help the clinician evaluate dynamic alignment. The purpose of this study was to determine how the knee rotates during dynamic knee valgus and whether the knee rotation is affected by toe direction (foot rotation).MethodsSixteen females performed dynamic knee valgus in three toe directions (neutral, toe-out, and toe-in) while maintaining the knee flexion angle at 30°. The knee rotation angle was evaluated using a 7-camera motion analysis system. Knee rotation was compared between the start position and the dynamic knee valgus position, as well as among the three toe directions, using repeated measures ANOVA models.ResultsThe knee significantly rotated externally in the dynamic knee valgus position compared with the start position in two toe directions (neutral and toe-out). A similar tendency was observed with the toe-in condition. Toe direction significantly affected the knee rotation angle. For toe-out and toe-in conditions, external and internal shifts of knee rotation compared with neutral were observed.ConclusionsThe knee rotates externally during dynamic knee valgus, and the knee rotation is affected by toe direction.Clinical RelevanceBecause of knee abduction and external rotation, the ACL may impinge on the femoral condyle in the case of dynamic valgus, especially in the toe-out position.     

Females with knee osteoarthritis use a detrimental knee loading strategy when squatting

BackgroundThe purpose of this study was to identify sex differences in lower limb kinematics, kinetics, and muscle activation patterns between individuals with osteoarthritis and healthy controls during a two-legged squat.MethodThirty OA (15 females) and 30 healthy (15 females) participants performed three 2-legged squats. Sagittal and frontal plane hip, knee, and ankle kinematics and kinetics were calculated. Two-way ANOVAs (Sex X OA Status) were used to characterize differences in squatting strategies between sexes and between those with and without knee OA.ResultsA greater decrease in sagittal hip, knee, and ankle range of motion and knee joint power was observed in the OA participants compared to the healthy controls. Females with OA had significantly reduced hip and knee adduction angles compared to the healthy females and males with OA. Females also had decreased hip power, hip flexion, and hip adduction moments and knee adduction moments compared to their male counterparts, with the greatest deficits observed in the females with OA. Females with OA also had the highest magnitude of muscle activation for the quadriceps, hamstrings, and gastrocnemius throughout the squat, while males with OA showed increased activation of the vastus lateralis and medial gastrocnemius compared to the healthy males.ConclusionsOA significantly altered biomechanics and neuromuscular control during the squat, with males employing a hip-dominant strategy, allowing them to achieve a greater lower limb range of motion.     

What predicts the first peak of the knee adduction moment?

BackgroundThe first peak of the knee adduction moment curve during walking has been shown to be a good clinical surrogate measure of medial tibiofemoral joint loading and osteoarthritis. Defining the relative contributions of the variables that dictate the knee adduction moment, such as center of mass, center of pressure, vertical ground reaction force, and knee adduction angle (i.e. lower limb alignment), has not been formally investigated within the same cohort of individuals. Therefore, the goal of this study was to determine which of these variables is the biggest determinant of the first peak of knee adduction moment curve.MethodsInstrumented gait analysis was collected for 30 individuals. Variables significantly correlated with the peak knee adduction moment were input into a stepwise multi-variable linear regression model.ResultsThe knee adduction angle predicted 58% of the variance in the first peak knee adduction moment and the vertical ground reaction force magnitude predicted the second most variance (20%).ConclusionsThe most effective way to modify the peak knee adduction moment may be to change the knee adduction angle (e.g. offloader brace), followed by changing the vertical magnitude of the ground reaction force (e.g. cane use).Clinical relevanceDefining the major determinants of the knee adduction moment may help guide clinicians in choosing conservative interventions to reduce it in conditions such as medial tibiofemoral osteoarthritis.     

Individual and cumulative measures of knee joint load associate with T2 relaxation times of knee cartilage in young,uninjured individuals: A pilot study

BackgroundArticular cartilage structure and chondrocyte health are sensitive and reliant on dynamic joint loading during activities. The purpose of this pilot study was to determine the association between measures of individual and cumulative knee joint loading with T2 relaxation times in the knee cartilage of young individuals without knee injury.MethodsTwelve participants (17–30 years old) without history of knee injury or surgery completed MRI, physical activity (PA), and biomechanical gait testing. T2 relaxation times were calculated in the cartilage within the patella and lateral and medial compartments. Accelerometry was used to measure mean daily step counts, minutes of PA, and % sedentary time over 7 days. Vertical ground reaction force, external knee joint moments and peak knee flexion angle were measured during stance phase of gait using three-dimensional motion capture. Cumulative knee joint loading was calculated as daily step count by external knee joint moment impulse. The relationship between measures of knee joint loading and T2 relaxation times was assessed using Pearson correlations.ResultsHigher T2 relaxation times in the femoral and tibial cartilage were consistently correlated to greater body mass, daily step counts, moderate and vigorous PA, and peak knee joint moments (r = 0.10–0.84). Greater cumulative knee flexion and adduction loading was associated with higher T2 relaxation times in the femoral and tibial cartilage (r = 0.16–0.65).ConclusionPreliminary findings suggest that individual loading factors and cumulative knee joint loading are associated with higher T2 relaxation times in the articular cartilage of young, healthy knees.