骨骼肌最大收缩力与最适初长度及其参数的研究

本实验以免载体股直肌为实验模型,研究了该肌在一定脉冲电流刺激下其初长度与收缩力、肌张力及肌力变化的相互关系。同时测定了正常生理状态下兔伸屈膝时股直肌拉长度的变化。结果表明:兔股直肌延长在1.0cm内时,肌力随初长度的延长而增大,超过1.0cm时增大已不明显(p<0.0 1),1.0cm与股直肌的生理最大延长度1.1cm相似。说明兔股直肌的初长度变化不应超过生理最大延长度。而人的骨骼肌与哺乳动物的骨骼肌没有本质的区别,因此,人骨骼肌的初长度变化也不应超过生理最大延长度。肌腱转位后的活动范围应在原位的生理活动范围内,才能发挥最佳收缩效应。     

The effects of voluntary contraction effort on quadriceps femoris electromyogram median frequency in humans: a muscle and sex comparison

The purpose of this study was to examine the effect of voluntary contraction efforts on the median frequency (f _med) of the electromyogram (EMG) recorded from the quadriceps femoris muscle in healthy men and women. A group of 30 healthy volunteers (15 men, 15 women) were assessed for EMG activity of the vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) muscles during isometric contractions with the knee at 60° flexion. Subjects performed a series of 5 s maximal voluntary isometric contractions that anchored the perceptual range with a "10" on a 10-point scale. Sub-maximal isometric contractions were then separately performed at the following perceived effort levels on the 10-point scale: 1, 2, 3, 4, 5, 6, 7, 8 and 9, in a random order. Subjects were instructed to maintain the contraction at each perceived level of effort for 5 s. The f _med of the three muscles was assessed using a power spectrum analysis performed over 11 consecutive, 512 ms, epochs overlapping each other by half their length during the middle 3 s of each contraction. The f _med for each of the 11 epochs was then determined for each muscle, followed by calculation of the means and normalized coefficients of variation [(standard deviation/mean)×100%] for each contraction. The results demonstrated that the mean f _med of VL was significantly greater than those of the other two muscles, and that f _med of RF was significantly greater than that of VM. The VL muscle demonstrated a significant increase in mean f _med across the contraction efforts, compared to the VM and RF muscles that displayed a significant decrease. The men displayed significantly higher f _med values for the VM muscle than did the women, as well as showing a significantly greater increase across the contraction efforts for the VL muscle. The variability of f _med was shown to be significantly higher for the VM muscle, compared to the VL and RF muscles. The findings of this study suggest that the f _med statistic is most sensitive to contraction intensity efforts for the VL muscle, and that men display significantly higher values for the VL and VM muscles, compared to women. Electronic Publication     

Eccentric and concentric torque-velocity characteristics of the quadriceps femoris in man

Summary The primary purpose of this investigation was to study the eccentric and concentric torque-velocity characteristics of the quadriceps femoris in man using a recently developed combined isometric, concentric and eccentric controlled velocity dynamometer (the SPARK System). A secondary purpose was to compare the method error associated with maximal voluntary concentric and eccentric torque output over a range of testing velocities. 21 males (21–32 years) performed on two separate days maximal voluntary isometric, concentric and eccentric contractions of the quadriceps femoris at 4 isokinetic lever arm velocities of 0° · s^–1 (isometric), 30° · s^–1 120° · s^–1 and 270° · s^–1. Eccentric peak torque and angle-specific torques (measured every 10° from 30° to 70°) did not significantly change from 0° · s^–1 to 270° · s^–1 (p>0.05) (with the exception of angle-specific 40° torque, which significantly increased;p<0.05). The mean method error was significantly higher for the eccentric tests (10.6%±1.6%) than for the concentric tests (8.1%±1.7%) (p<0.05). The mean method error decreased slightly with increasing concentric velocity (p>0.05), and increased slightly with increasing eccentric velocity (p>0.05). A tension restricting neural mechanism, if active during maximal eccentric contractions, could possibly account for the large difference seen between the present eccentric torque-velocity results and the classic results obtained from isolated animal muscle.     

股后区主要穿支的形态学分析与皮瓣设计

目的：为股后区穿支皮瓣的临床应用提供解剖学依据。方法：6具（12侧）动脉灌注明胶．氧化铅混悬液的新鲜成人整尸标本，解剖观测股后区外径≥0．5mm的穿支，测量其管径及其走行、分支与分布情况等。取下整个下肢被覆组织拍摄X线片，观测皮动脉的数量以及彼此间的吻合情况等。利用Photoshop与Scion Image分析穿支供血的趋向性及每个分支的供血面积等。结果：股后区共有穿支（外径≥0．5mm）27支，其中65％为皮穿支，35％为肌皮穿支。平均外径为0．8mm，平均蒂长为2．93cm。自股深动脉之穿动脉发出者平均长度为6．81cm。每侧穿动脉在股后区供血面积平均为229cm^2，平均每个穿支供血面积为43cm^2。结论：股后区的皮肤穿支管径较粗，营养皮肤面积较大，以股后诸穿支为蒂设计的穿支皮瓣可为下肢或身体其它部位皮肤移植提供：①游离皮瓣；②近端蒂皮瓣；③远端蒂皮瓣。     

Quadriceps-hamstring EMG activity during functional, closed kinetic chain exercise to fatigue

It has been hypothesized that the ability of the neuromuscular system to co-contract muscles for joint stabilization may be impaired during the development of fatigue. The purpose of this study was to examine muscle activation of the quadriceps and hamstring muscles during a prolonged closed kinetic chain exercise, the forward lunge. Eight males and two females [mean (SD) age 26.0 (2.3) years, height 177.2 (13.6) cm, body mass 82.8 (17.1) kg] with no prior knee pathology volunteered for this study. Subjects performed repeated forward lunges onto their dominant leg at the cadence of one full lunge cycle every 2 s, until the point of volitional failure. Digital switches were positioned to record foot-strike and knee-strike of the lunge leg at the midpoint of the lunge, as well as heel-strike upon return to stance. During the lunge performance, surface electromyographic (EMG) signals of the vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), and semitendinosus (ST) muscles of the supporting leg were measured. Heart rate was also monitored every 30 s during the performance. All EMG data were full-wave rectified, partitioned into up and down phases, and integrated over the entire exercise period. The results demonstrated a significant increase in activation of the VL, VM, and BF during performance of the forward lunge to volitional failure (P < 0.05). No significant increase was shown for the ST. Heart rate increased significantly over the course of the lunge. These findings suggest that activation of the VL, VM, and BF muscles occurs as a unit during performance of the forward lunge during both concentric and eccentric lunge phases. Accepted: 25 October 1999     

Distal rectus femoris surgery in children with cerebral palsy: results of a Delphi consensus project

PurposeThe purpose of this study was for an international panel of experts to establish consensus indications for distal rectus femoris surgery in children with cerebral palsy (CP) using a modified Delphi method.MethodsThe panel used a five-level Likert scale to record agreement or disagreement with 33 statements regarding distal rectus femoris surgery. The panel responded to statements regarding general characteristics, clinical indications, computerized gait data, intraoperative techniques and outcome measures. Consensus was defined as at least 80% of responses being in the highest or lowest two of the five Likert ratings, and general agreement as 60% to 79% falling into the highest or lowest two ratings. There was no agreement if neither threshold was reached.ResultsConsensus or general agreement was reached for 17 of 33 statements (52%). There was general consensus that distal rectus femoris surgery is better for stiff knee gait than is proximal rectus femoris release. There was no consensus about whether the results of distal rectus femoris release were comparable to those following distal rectus femoris transfer. Gross Motor Function Classification System (GMFCS) level was an important factor for the panel, with the best outcomes expected in children functioning at GMFCS levels I and II. The panel also reached consensus that they do distal rectus femoris surgery less frequently than earlier in their careers, in large part reflecting the narrowing of indications for this surgery over the last decade.ConclusionThis study can help paediatric orthopaedic surgeons optimize decision-making for, and outcomes of, distal rectus femoris surgery in children with CP.Level of evidenceV     

Functionally complex muscles of the cat hindlimb

The biceps femoris (BF) muscle is divided into three neuromuscular compartments defined by the innervation patterns of the main nerve branches (English and Weeks 1987). The goals of this study were i) to determine how different regions of the biceps femoris muscle are activated in the intact cat during a broad range of limb movements evoked by perturbations of stance posture, and ii) to determine the relationship between the anatomical compartments of biceps femoris and the functional units as defined in this task. Cats were trained to stand on a moveable platform with each paw on a triaxial force plate. The animal's stance was perturbed by linear translation of the platform in each of sixteen different directions in the horizontal plane. EMG activity was recorded from eight sites across the width of the left biceps femoris muscle. During quiet stance only the anterior compartment was tonically active, presumably contributing to hip extensor torque in the maintenance of stance. During platform translation, evoked EMG activity was recorded from each electrode pair for a wide range of directions of perturbation; as direction changed progressively, the amplitude of evoked activity from any electrode pair increased to a maximum and then decreased. When the EMG amplitude was plotted in polar coordinates as a function of translation direction, the region of response formed a petal shaped area in the horizontal plane, termed the EMG tuning curve. The compartments of the BF muscle were not activated homogeneously. The tuning curve of the anterior BF compartment was similar to that of other hip extensors, and coincided with the region of postero-lateral force production by the hindlimb against the support. The tuning curve of the middle BF compartment was shifted in a counterclockwise direction from that of the anterior compartment, but overlapped extensively with it; the middle BF tuning curve was similar to that of anterior gracilis. The tuning curve of the posterior biceps compartment was rotated further counterclockwise and overlapped very little with that of the middle BF compartment. The posterior BF was activated in a pattern similar to that of other knee flexors. The functional units of BF activation were not identical with the neuromuscular compartments defined by the main nerve branches. As direction of the perturbation changed, the region of BF that was activated moved progressively across the muscle. This progression of the active region was continuous across BFa and BFm, whereas there was a jump, or discontinuity at the border between BFm and BFp.(ABSTRACT TRUNCATED AT 400 WORDS)     

带血管蒂阔筋膜张肌及腱膜转位修补巨型腹股沟疝的应用解剖

目的:为带血管蒂阔筋膜张肌及腱膜转位修补巨型腹股沟疝提供解剖学基础。方法:在30例成人下肢标本上解剖观测了阔筋膜张肌的动脉血管分布,神经支配,肌腹和肌腱的长度等。结果:阔筋膜张肌动脉来源有旋股外侧动脉和臀上动脉,该肌由臀上神经支配,肌腹长度为112.31±3.13mm,髂经束的长度为315±6.8mm,额前上棘水平至腹肌外侧缘的距离,男性为168±7.5mm,女性为176±6.8mm。结论:阔筋膜张肌血供丰富,肌腱膜长,位置邻近腹股沟区,可作为巨型腹股沟疝修补的供体。     

Dietary Restriction Reduces the Prevalence of Osteonecrosis of the Caput Femoris in Spontaneously Hypertensive Rats

We investigated the effects of dietary restriction (DR), an experimental intervention known to suppress several strain-specific diseases, on the prevalence of osteonecrosis of the caput femoris in spontaneously hypertensive rats (SHR). At 6 weeks of age, the food intake of DR rats was restricted to 65% of the mean intake of control rats fed ad libitum (AL). Acute osteonecrosis of the caput femoris without reparative tissue response (RTR) was observed at 10 and 15 weeks in both DR and AL groups; no such acute lesion was seen at 20 and 30 weeks. The prevalence of osteonecrosis, osteonecrosis with/without reparative tissue response was significantly reduced in DR rats at 15 and 20 weeks, but not at 10 weeks. DR reduced the body weight by 30% and the length of the femur by 10%. Ossification of the caput femoris, known to be delayed in AL rats compared with Wistar Kyoto rats, was also restored by DR. Our results showed that dietary restriction reduced the prevalence of osteonecrosis and modulated the mechanical factors involved in the lesion. They also indicate that utilization of dietary restriction is a useful research tool for investigating the underlying mechanisms of osteonecrosis of the caput femoris in SHR. Received: 4 March 1997 / Accepted: 9 July 1998