Comparative anatomy and muscle architecture of selected hind limb muscles in the Quarter Horse and Arab

The Quarter Horse (bred for acceleration) and the Arab (bred for endurance) are situated at either end of the equine athletic spectrum. Studies into the form and function of the leg muscles in human sprint and endurance runners have demonstrated that differences exist in their muscle architecture. It is not known whether similar differences exist in the horse. Six Quarter Horse and six Arab fresh hind limb cadavers were dissected to gain information on the muscle mass and architecture of the following muscles: gluteus medius; biceps femoris; semitendinosus; vastus lateralis; gastrocnemius; tibialis cranialis and extensor digitorum longus. Specifically, muscle mass, fascicle length and pennation angle were quantified and physiological cross-sectional area (PCSA) and maximum isometric force were estimated. The hind limb muscles of the Quarter Horse were of a significantly greater mass, but had similar fascicle lengths and pennation angles when compared with those of the Arab; this resulted in the Quarter Horse hind limb muscles having greater PCSAs and hence greater isometric force potential. This study suggests that Quarter Horses as a breed inherently possess large strong hind limb muscles, with the potential to accelerate their body mass more rapidly than those of the Arab.     

Atlas of the muscle motor points for the lower limb: implications for electrical stimulation procedures and electrode positioning

The aim of the study was to investigate the uniformity of the muscle motor point location for lower limb muscles in healthy subjects. Fifty-three subjects of both genders (age range: 18–50 years) were recruited. The muscle motor points were identified for the following ten muscles of the lower limb (dominant side): vastus medialis, rectus femoris, and vastus lateralis of the quadriceps femoris, biceps femoris, semitendinosus, and semimembranosus of the hamstring muscles, tibialis anterior, peroneus longus, lateral and medial gastrocnemius. The muscle motor point was identified by scanning the skin surface with a stimulation pen electrode and corresponded to the location of the skin area above the muscle in which an electrical pulse evoked a muscle twitch with the least injected current. For each investigated muscle, 0.15 ms square pulses were delivered through the pen electrode at low current amplitude (<10 mA) and frequency (2 Hz). 16 motor points were identified in the 10 investigated muscles of almost all subjects: 3 motor points for the vastus lateralis, 2 motor points for rectus femoris, vastus medialis, biceps femoris, and tibialis anterior, 1 motor point for the remaining muscles. An important inter-individual variability was observed for the position of the following 4 out of 16 motor points: vastus lateralis (proximal), biceps femoris (short head), semimembranosus, and medial gastrocnemius. Possible implications for electrical stimulation procedures and electrode positioning different from those commonly applied for thigh and leg muscles are discussed.     

Morphological evaluation of the baboon hind limb muscles based on relative weight

Morphological features of the hind limb muscles reflect the muscular function correlating with the locomotion. In this study, the muscles of the baboon hind limb were weighed and the relative muscle weights were compared with those of the human lower extremity. In the baboon, the biceps femoris was the largest (11.60%) and the vastus lateralis (10.67%) was placed second. The gluteus medius (8.55%) among the hip muscles and the gastrocnemius (4.38%) among the leg muscles were predominant in each segment. The relative weights of the gluteus medius and the biceps femoris were especially larger in the baboon than in the human, while the gluteus maximus and the soleus were larger in the human. The baboon gluteus medius and biceps femoris chiefly generate the propulsive power during quadrupedal locomotion and the human soleus is essential for the erect bipedalism.     

Length and moment arm of human leg muscles as a function of knee and hip-joint angles

Summary Lengths of muscle tendon complexes of the quadriceps femoris muscle and some of its heads, biceps femoris and gastrocnemius muscles, were measured for six limbs of human cadavers as a function of knee and hip-joint angles. Length-angle curves were fitted using second degree polynomials. Using these polynomials the relationships between knee and hip-joint angles and moment arms were calculated. The effect of changing the hip angle on the biceps femoris muscle length is much larger than that of changing the knee angle. For the rectus femoris muscle the reverse was found. The moment arm of the biceps femoris muscle was found to remain constant throughout the whole range of knee flexion as was the case for the medial part of the vastus medialis muscle. Changes in the length of the lateral part of the vastus medialis muscle as well as the medial part of the vastus lateralis muscle are very similar to those of vastus intermedius muscle to which they are adjacent, while those changes in the length of the medial part of the vastus medialis muscle and the lateral part of the vastus lateralis muscle, which are similar to each other, differ substantially from those of the vastus intermedius muscle. Application of the results to jumping showed that bi-articular rectus femoris and biceps femoris muscles, which are antagonists, both contract eccentrically early in the push off phase and concentrically in last part of this phase.     

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。     

Muscle architecture and functional anatomy of the pelvic limb of the ostrich (Struthio camelus)

The functional anatomy of the pelvic limb of the ostrich (Struthio camelus) was investigated in order to assess musculoskeletal specialization related to locomotor performance. The pelvic limbs of ten ostriches were dissected and detailed measurements of all muscle tendon units of the pelvic limb were made, including muscle mass, muscle length, fascicle length, pennation angle, tendon mass and tendon length. From these measurements other muscle properties such as muscle volume, physiological cross-sectional area (PCSA), tendon cross-sectional area, maximum isometric muscle force and tendon stress were derived, using standard relationships and published muscle data. Larger muscles tended to be located more proximally and had longer fascicle lengths and lower pennation angles. This led to an expected proximal to distal reduction in total muscle mass. An exception to this trend was the gastrocnemius muscle, which was found to have the largest volume and PCSA and also had the highest capacity for both force and power production. Generally high-power muscles were located more proximally in the limb, while some small distal muscles (tibialis cranialis and flexor perforatus digiti III), with short fibres, were found to have very high force generation capacities. The greatest proportion of pelvic muscle volume was for the hip extensors, while the highest capacity for force generation was observed in the extensors of the ankle, many of which were also in series with long tendons and thus were functionally suited to elastic energy storage.     

膝骨关节炎患者膝关节置换后下肢肌的表面肌电图变化

背景：膝骨关节炎患者膝关节置换后下肢肌功能恢复一直存在着争议。 目的：评价膝骨关节炎患者膝关节置换手术后下肢肌肉功能。 方法：应用TELEMYO 2400R G2表面肌电图遥测仪对25例双膝骨关节炎单膝关节置换后患者在平常自然步态下进行双下肢股直肌、胫前肌、股二头肌和腓肠肌内侧的表面肌电信号测试。在肌电图测试前,对患者双膝关节功能进行美国特种外科医院膝关节评分。 结果与结论：患者置换后美国特种外科医院膝关节评置换侧平均分91.44,其优良率达100%;未置换侧平均分54.52。置换侧在疼痛、关节功能方面有明显改善;膝关节置换后置换侧股直肌、胫前肌、股二头肌的肌电振幅、肌电积分、平均频率、中位频率的(平均值、最小值、最大值)与未置换侧相比差异无显著性意义(P > 0.05);置换侧腓肠肌内侧肌电振幅值及肌电积分值显著大于未置换侧(P < 0.05);置换侧腓肠肌内侧平均频率、中位频率与未置换侧相比差异无显著性意义(P > 0.05)。提示膝关节置换后置换侧的下肢肌没有恢复到正常的功能活动水平,因此膝关节置换后康复要特别重视患者的肌肉锻炼。中国组织工程研究杂志出版内容重点：人工关节;骨植入物;脊柱;骨折;内固定;数字化骨科;组织工程全文链接：     

Differences of morphometrical parameters in hind limb muscle fibres between ovarectomized and sexually intact female dogs.

Slow and fast twitch fibres of the Mm. tibialis cranialis, semitendinosus and sartorius of seven sexually intact and seven ovarectomized female beagles were histochemically and morphometrically analysed. Along with type I and type IIA fibres, another main type II fibre (IIS), which seems to be peculiar to the dog, was found in the Mm. semitendinosus and tibialis cranialis. Type I fibers comprised 26% and type II fibres 74% of all recorded muscle fibres in the M. tibialis cranialis, 29% (type I) and 71% (type II) in the M. semitendinosus and 51% (type I) and 49% (type II) in the M. sartorius, respectively. The average single profile area and the corresponding mean diameter of fibre types I and II in the investigated hind limb muscles were generally larger in ovarectomized than in sexually intact animals. This was more evident in type II than in type I fibres. However only the type II fibres of the M. tibialis cranialis and sartorius exhibited a statistically significant increase in diameter (p < 0.01 and p < 0.05, respectively). Accordingly, the mean density (number of fibres/mm2) of both fibre types in the hind limb muscles of spayed dogs was generally reduced. Again, this reduction attained statistical relevance in the type I and II fibres of the tibialis cranialis. In addition, the fibre densities of type I in the semitendinosus and type II in the sartorius muscles were also significantly reduced in ovarectomized dogs. In conclusion, ovarectomized beagles showed a generally increased mean diameter of the investigated type I and II hind limb muscle fibres and a concomitant decreased average fibre density of the respective types when compared to sexually intact animals.     

Synchronization of lower limb motor unit activity during walking in human subjects

Synchronization of motor unit activity was investigated during treadmill walking (speed: 3-4 km/h) in 25 healthy human subjects. Recordings were made by pairs of wire electrodes inserted into the tibialis anterior (TA) muscle and by pairs of surface electrodes placed over this muscle and a number of other lower limb muscles (soleus, gastrocnemius lateralis, gastrocnemius medialis, biceps femoris, vastus lateralis, and vastus medialis). Short-lasting synchronization (average duration: 9.6 +/- 1.1 ms) was observed between spike trains generated from multiunit electromyographic (EMG) signals recorded by the wire electrodes in TA in eight of nine subjects. Synchronization with a slightly longer duration (12.8 +/- 1.2 ms) was also found in 13 of 14 subjects for paired TA surface EMG recordings. The duration and size of this synchronization was within the same range as that observed during tonic dorsiflexion in sitting subjects. There was no relationship between the amount of synchronization and the speed of walking. Synchronization was also observed for pairs of surface EMG recordings from different ankle plantarflexors (soleus, medial gastrocnemius, and lateral gastrocnemius) and knee extensors (vastus lateralis and medialis of quadriceps), but not or rarely for paired recordings from ankle and knee muscles. The data demonstrate that human motor units within a muscle as well as synergistic muscles acting on the same joint receive a common synaptic drive during human gait. It is speculated that the common drive responsible for the motor unit synchronization during gait may be similar to that responsible for short-term synchronization during tonic voluntary contraction.     

穿戴塑料踝足矫形器对下肢肌肉疲劳性的影响

背景：目前尚未见到系统研究踝足矫形器对下肢肌肉影响的文献。 目的：提取正常人穿戴固定踝足矫形器时的下肢肌电信号,分析固定踝足矫形器对下肢肌肉疲劳性的影响。 方法：选择5名健康男性受试者参加试验,每名受试者分别进行3组试验：①第1组,在不穿戴任何矫形器的情况下以自然步态行走。②第2组,受试者穿戴平跟踝足矫形器以自然步态行走(此时矫形器踝部包裹超过踝中心1 cm,记1.0 cm),穿戴同一矫形器但在踝部去掉1.0 cm、踝部塑料边缘刚好通过踝中心时采集(记     0 cm),在踝部再去掉1.0 cm后以自然步态行走(记-1.0 cm)。③第3组,受试者穿戴1.5 cm正常跟高踝足矫形器以自然步态行走,穿戴同一矫形器,但跟高分别改为1.0,2.0 cm后以自然步态行走。行走中采用肌电采集仪检测受试者下肢股二头肌、股直肌、胫骨前肌、腓肠肌的表面肌电信号。 结果与结论：①正常不穿戴任何矫形器时,4块肌肉的肌电信号是最弱的。②对于任何一块肌肉,正常不穿戴矫形器时所对应肌电值比穿戴不同硬度矫形器时所对应的肌电值要小。③对于股二头肌,正常不穿戴矫形器时所对应的积分肌电值与穿戴正常跟高矫形器时所对应的值很接近,同时这两个值要比穿戴不正常跟高矫形器时所对应的积分肌电值小。表明固定塑料踝足矫形器会引起股二头肌、股直肌、胫骨前肌、腓肠肌的疲劳,当固定塑料踝足矫形器的跟高不合适时会进一步增加股二头肌的疲劳程度。中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程全文链接：     

Muscle architecture of biceps brachii, triceps brachii and supraspinatus in the horse

Three muscles from the proximal equine forelimb were dissected in order to investigate their potential to contribute to proximal limb mechanics. Muscle mass, fibre length, tendon mass and tendon length were measured from biceps brachii, triceps brachii, supraspinatus and lacertus fibrosus (biceps lateral head mass 171-343.4 g and fibre length 0.5-0.8 cm; biceps medial head mass 283-500 g and fibre length 2.2-4 cm; biceps tendon mass 121.8-260 g and tendon length 35-44 cm; triceps long head mass 3200-6663 g and fibre length 19-26.3 cm; triceps lateral head mass 513.8-1240 g and fibre length 17.5-24 cm; triceps medial head mass 85.2-270.6 g and fibre length 9-16.8 cm; supraspinatus mass 793-1546 g and fibre length 4.7-12.4 cm; lacertus fibrosus mass 4.6-12.4 g and length 10-16 cm). Physiological cross-sectional area (PCSA) and maximum isometric force were estimated for each muscle, and moment arm measurements were taken at the shoulder and elbow joints. Biceps has a greater isometric force-generating capacity than supraspinatus. It also appears to have a larger shoulder moment arm, so could therefore have the potential to make a greater contribution to the shoulder moment than supraspinatus. Supraspinatus is likely to function primarily as a shoulder stabilizer rather than a shoulder extensor. Biceps also functions as an elbow flexor and data here indicate that it has a greater PCSA and isometric force-generating capacity than its antagonist triceps brachii. Calculation of tendon forces showed that the biceps tendon can withstand much greater forces than lacertus fibrosus. This study will enable further investigation into the interaction between energy recycling in elastic tissues and the generation and absorption of mechanical work by adjacent muscle groups in the equine forelimb.     

基于AnyBody仿真和肌电测试分析不同体质量指数男性青年球类运动中的生物力学特征

文题释义： Anybody仿真：使用数学建模技术模拟人体肌肉骨骼在不同载荷中的情况,计算各块肌肉和关节的受力、变形、肌腱的弹性能、拮抗肌肉运动和其他对于工作中的人体有用的特性,以计量方式计算出人体对于环境的反应,兼与人机工程学和生物力学分析,为人体运动建模、人机工程学产品性能改进和生物医学工程研究提供平台。 均方根振幅：是将振幅平方的平均值开平方,把振幅值平均然后开方,最原始的是针对正弦波推导出来的,但实际上对所有的波形都适用,均方根值(RMS)也称作为效值,表示在一段周期内,参加肌肉活动的肌肉瞬间肌电图振幅均方根值,是一定时间内肌电位值平方和的平方根。 背景：Anybody肌肉骨骼建模系统,使用数学建模技术模拟人体骨骼、肌肉和环境的关系,可对人体的逆向动力学进行研究,得出下肢三关节最大肌肉力等指标。 目的：研究24名不同体质量指数男大学生在坐瑞士球一个动作周期的下肢肌肉力值,及受试者在坐瑞士球与平凳的均方根肌电平均值对比情况。 方法：将24名男大学生按体质量指数分为正常组、超重组、肥胖组,用BTS三维红外动作捕捉系统、Kistler 三维测力台、BTS表面肌电测试系统,同步记录动力学和肌电参数,以单因素方差分析定性比较不同组间肌力和肌电参数差异,用定量差异分析法对比均值差异。 结果与结论：①肌肉力量方面,由坐到站过程中,正常组与肥胖组相比,股直肌、半膜肌、股二头肌长头、腘肌、比目鱼肌、胫骨前肌差异显著(P < 0.05,0.47≤QD<0.80),股方肌与耻骨肌的两组肌肉力差异极其显著(P < 0.01,QD≥0.80);超重组与肥胖组肌肉力相比,股方肌具有显著性差异(P < 0.05,0.47≤QD<0.80),由站到坐过程中,正常组与肥胖组相比,缝匠肌、拇长伸肌、腓肠肌肌肉力差异显著(P < 0.05,0.47≤QD<0.80);②均方根肌电值方面,坐平凳状态下,由坐到站过程中,正常组与肥胖组相比,股二头肌和腓肠肌差异显著(P < 0.05,0.47≤QD<0.80),由站到坐过程中,正常组与肥胖组相比,股直肌差异显著(P < 0.05,0.47≤QD<0.80);坐瑞士球状态下,由坐到站过程中,正常组与肥胖组相比,胫骨前肌、股二头肌差异显著(P < 0.05,0.47≤QD<0.80);由站到坐过程中,正常组与肥胖组相比,腓肠肌、右竖脊肌肌电值差异显著(P < 0.05,0.47≤QD<0.80)。提示：①各组由坐到站过程中主导发力肌肉是臀中肌、股外侧肌、股二头肌长头、股直肌、腓肠肌、胫骨前肌、比目鱼肌,由站到坐过程中下肢臀中肌、股外侧肌和股二头肌长头、腓肠肌、胫骨前肌、比目鱼肌主导发力;②与坐平凳相比,受试者在坐瑞士球时胫骨前肌、股直肌、股二头肌、腓肠肌均方根肌电值高。ORCID: 0000-0003-0520-5606(庞博) 中国组织工程研究杂志出版内容重点：人工关节;骨植入物;脊柱;骨折;内固定;数字化骨科;组织工程     

Gait and surface electromyography characteristics in hurdle athletes in a total gait cycle北大核心

BACKGROUND: In recent years, the technical parameters about hurdle athletes are mainly obtained through video analysis and DLT algorithm. However, the gait and surface electromyography (sEMG) characteristics during normal walking are little reported. OBJECTIVE: To explore the changes of the gait and lower limb sEMG signals relative to gait period in hurdle athletes. METHODS: Eight male professional hurdlers were selected to perform gait and lower limb sEMG tests on the trail, and the differences in gait and sEMG signals were analyzed by mathematical statistics. RESULTS AND CONCLUSION: The gait parameters of hurdlers showed no significant differences (except step length). In the total gait cycle, along with the gait changing, the right and left side muscles of the same name moved alternately. The median frequency and average power frequency of the tapping leg in the lower limb muscles were greater than those of the swinging leg (except biceps femoris, tibialis anterior and lateral gastrocnemius), but the mean EMG and EMG integral values of the tapping leg were smaller than those of the swinging leg. At the stand phase, the median frequency and average power frequency of the tapping leg in the lower limb muscles were greater than those of the swinging leg (except tibialis anterior), but the mean EMG and EMG integral values of the tapping leg were smaller than those of the swinging leg (except soleus). At the swing phase, the median frequency and average power frequency of the tapping leg in the lower limb muscles were greater than those of the swinging leg (except tibialis anterior and lateral gastrocnemius), but the mean EMG and EMG integral values of the tapping leg were smaller than those of the swinging leg (except soleus). To conclude, there are different degrees of differences in the frequency domain and time domain of the lower limb muscles between tapping and swinging legs. Additionally, the muscle strength of the tapping leg is less than that of the swinging leg. © 2017, Journal of Clinical Rehabilitative Tissue Engineering Research. All rights reserved.     

Modulation of locomotor activity in complete spinal cord injury

The aim of this study was to evaluate the modulation of muscle activity during locomotor-like movements by different walking speeds in subjects with a motor complete spinal cord injury (SCI) compared to actively- and passively-walking control subjects without neurological deficit. Stepping movements on a treadmill were induced and assisted by a driven gait orthosis. Electromyographic (EMG) muscle activity of one leg (rectus and biceps femoris, tibialis anterior and gastrocnemius) was recorded and analyzed at three stepping velocities with similar body weight support in both subject groups. In SCI subjects, the EMG amplitude of biceps femoris, tibialis anterior and gastrocnemius was in general similar or weaker than in passively- and actively-stepping control subjects, but that of rectus femoris was larger. The degree of co-activation between tibialis anterior and gastrocnemius was higher in SCI than in control subjects. A significant velocity-dependent EMG modulation was present in all four-leg muscles in both subject groups. In SCI subjects, this EMG modulation was similar to that in actively stepping control subjects. It is concluded that in complete spastic SCI subjects, spinal neuronal circuits underlying locomotion can to a large extent adequately respond to a change in external drive to adapt the neuronal pattern to a new locomotion speed. The application of various speeds might enhance the effect of locomotor training in incomplete SCI subjects.     

自然行走对人体足底压力与下肢表面肌电信号影响的研究

目的 探究自然行走对正常人足底压力与下肢肌肉表面肌电信号(sEMG)的影响.方法 分别测量28例健康青年男性受试者在30 min平地自然行走前后足底压力与下肢肌肉的sEMG,得到行走前后峰值压强、冲量等足底压力参数及胫骨前肌、腓肠肌、股直肌与股二头肌的表面肌电时域参数积分肌电(iEMG)和频域参数平均功率频率(MPF),并检验峰值压强与身高、体质量的相关性.结果 平地自然行走开始时和30 min后,其左、右侧的峰值压强、冲量等各特征参数的差异均有统计学意义(均P＜0.05),不同参数的左、右侧差异分别体现在足底不同区域,而在跖骨区M3、M4、M5处各参数均表现出左侧大于右侧;行走前后左侧胫骨前肌、腓肠肌、骨直肌与股二头肌sEMG的iEMG均大于右侧;行走前后左侧胫骨前肌、腓肠肌的MPF大于右侧,其差异具有统计学意义(P＜0.05).30 min行走后右足脚趾区Toe2-5的峰值压强降低,其差异具有统计学意义(P＜0.05);各肌肉表面肌电iEMG无显著性变化,左侧股直肌的表面肌电信号的MPF显著性下降;峰值压强与身高、体质量均呈弱相关.结论 正常人自然行走中,足底压力和下肢表面肌电均具有左右侧的差异;30 min自然行走尚未导致足底压力出现明显疲劳状态的相应结果,因此自然行走30 min可维持步态的稳定性;30 min行走将导致左侧股直肌出现疲劳.     

Evaluation of the ability to make non-invasive estimation of muscle contractile properties on the basis of the muscle belly response

The histochemical and biomechanical relationships of limb muscles are examined in two groups of 15 men aged between 17 and 40 years. Seven muscles are chosen: biceps brachii, triceps brachii (TB), flexor digitorum superficialis, extensor digitorum, biceps femoris, tibialis anterior and gastrocnemius caput mediale (GCM). The aim of the preliminary study is to evaluate an alternative method based on a tensiomyographic (TMG) non-invasive measurement technique. The percentage of type I muscle fibres obtained with the histochemical method is 2.2 times higher for the slowest measured muscle (GCM) than for the fastest (TB). The contraction time of a muscle belly twitch response measured by TMG is 1.9 times higher for GCM than for TB. Statistical analysis of the data obtained by tensiomyographic and histochemical techniques shows a significant correlation between the contraction time of muscle response measured by TMG and the percentage of type I muscle fibres (correlation coefficient equals 0.93). Results of the study suggest using the TMG measuring technique as a basis for the estimation of the percentage of type I muscle fibres.     

Muscle moment arms of the gibbon hind limb: implications for hylobatid locomotion

Muscles facilitate skeletal movement via the production of a torque or moment about a joint. The magnitude of the moment produced depends on both the force of muscular contraction and the size of the moment arm used to rotate the joint. Hence, larger muscle moment arms generate larger joint torques and forces at the point of application. The moment arms of a number of gibbon hind limb muscles were measured on four cadaveric specimens (one Hylobates lar, one H. moloch and two H. syndactylus). The tendon travel technique was used, utilizing an electro‐goniometer and a linear voltage displacement transducer. The data were analysed using a technique based on a differentiated cubic spline and normalized to remove the effect of body size. The data demonstrated a functional differentiation between voluminous muscles with short fascicles having small muscle moment arms and muscles with longer fascicles and comparatively smaller physiological cross‐sectional area having longer muscle moment arms. The functional implications of these particular configurations were simulated using a simple geometric fascicle strain model that predicts that the rectus femoris and gastrocnemius muscles are more likely to act primarily at their distal joints (knee and ankle, respectively) because they have short fascicles. The data also show that the main hip and knee extensors maintain a very small moment arm throughout the range of joint angles seen in the locomotion of gibbons, which (coupled to voluminous, short‐fascicled muscles) might help facilitate rapid joint rotation during powerful movements.     

Atrophy of the lower limbs in elderly women: is it related to walking ability?

This study investigated the relationship between walking ability and age-related muscle atrophy of the lower limbs in elderly women. The subjects comprised 20 young women and 37 elderly women who resided in nursing homes or chronic care institutions. The elderly subjects were divided into three groups according to their walking ability. The muscle thickness of the following ten lower limb muscles were measured by B-mode ultrasound: the gluteus maximus, gluteus medius, gluteus minimus, psoas major, rectus femoris, vastus lateralis, vastus intermedius, biceps femoris, gastrocnemius and soleus. Compared to the young group, muscle thicknesses of all muscles except the soleus muscle were significantly smaller in all the elderly groups. There were no significant differences between the fast- and slow-walking groups in the thickness of any muscle. In the dependent elderly group, noticeable muscle atrophy was observed in the quadriceps femoris muscle. The results of this study suggest that the elderly who are capable of locomotion, regardless of their walking speed, show a moderate degree of age-related atrophy, while those who do not walk exhibit more severe atrophy, especially in the quadriceps femoris muscle.     

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。     

Differences in leg muscle activity during running and cycling in humans

Delta (Δ) efficiency is defined as the ratio of an increment in the external mechanical power output to the increase in metabolic power required to produce it. The purpose of the present study was to investigate whether differences in leg muscle activity between running and cycling can explain the observed difference in Δ efficiency between the two activities. A group of 11 subjects performed incremental submaximal running and cycling tests on successive days. The Δ efficiencies during running and cycling were based on five exercise stages. Electromyograph (EMG) measurements were made of three leg muscles (gastrocnemius, vastus lateralis and biceps femoris). Kendall's correlation coefficients between the mean EMG activity and the load applied were calculated for each muscle, for both running and cycling. As expected, the mean Δ efficiency during running (42%) was significantly greater than that during cycling (25%). For cycling, all muscles showed a significant correlation between mean EMG activity and the load applied. For running, however, only the gastrocnemius muscle showed a significant, but low correlation (r=0.33). The correlation coefficients of the vastus lateralis and biceps femoris muscles were not significantly different from 0. The results were interpreted as follows. In contrast to cycling, which includes only concentric contractions, during running up inclines eccentric muscle actions play an important role. With steeper inclines, more concentric contractions must be produced to overcome the external force, whereas the amount of eccentric muscle actions decreases. This change in the relative contribution of concentric and eccentric muscle actions, in combination with the fact that eccentric muscle actions require much less metabolic energy than concentric contractions, can explain the difference between the running and cycling Δ efficiency. Electronic Publication