Electromyographyc evaluation of movements of lower limb in double pulley system equipment: comparison between gastrocnemius (caput laterale) and gluteus maximus

It was evaluated movements of lower limb in the double pulley system equipment on ten male volunteers during contraction of gastrocnemius (caput laterale) and gluteus maximus muscles in the following movements: 1) hip extension with extended knee and erect trunk, 2) hip extension with flexed knee and erect trunk, 3) hip extension with flexed knee and erect trunk, 3) hip extension with extended knee and inclined trunk, 5) hip abduction along the midline, 7) hip abduction with extension beyond the midline, 8) adduction with hip flexion beyond the midline, 8) adduction with hip flexion beyond the midline, and 9) adduction with hip extension beyond the midline. Myoelectric signals were taken up by Lec Tec surface electrodes connected to a 6-channel Lynx electromyographic signal amplifier coupled with a computer equipped with a model CAD 10/26 analogue digital conversion board and with a specific software for signal recording and analysis. We observed weak gastrocnemius muscle activity for all movements studied. In the case of gluteus maximus, the most important potentials were observed for movement 2, while for the remaining movements the actions were of reasonable intensity. Compared to gluteus, gastrocnemius was less required for all movements.     

Interjoint coordination in lower limbs during different movements in humans

Redundancy is associated with the ability of the nervous system to select different interjoint coordinations and movement trajectories to achieve the same motor goal. The nervous system may coordinate multiple degrees of freedom (DF) by combining them in a task-specific way to control them as a unit or synergy. Some movements may be accomplished using only one synergy, whereas other movements may employ several synergies. To investigate the problem of interjoint coordination, we applied principal component (PC) analysis to eight types of movement in healthy male subjects: forward squats, backward squats, sideways squats, squats on one leg, walking three steps, stepping in place, going up a step, and going down a step. Angular changes in four DF were analyzed: thigh flexion-extension, knee flexion-extension, ankle flexion-extension, thigh abduction-adduction, with the former three DF investigated in all movements. For many movements, two synergies were sufficient to account for more than 95% of DF angular excursions. Squatting on one leg could be described using only one synergy (99%). The angle between the vectors representing PCs for movements produced with the right and left legs could be less than 10° for some movements but could reach 25° for other movements. The nervous system may thus use somewhat different interjoint coordinations while producing movements on the right and the left sides. The angle between the first PCs of different movements could be smaller than 10°. Thus there may be a common but adjustable basic synergy that is used to produce different movements. Additional synergies provide the transition from one movement to another. Electronic Publication     

Electromyographic analysis of the rectus abdominis muscle in pelvic retroversion and the decrease of the lower limbs

We often face patients searching for rehabilitation for lower back disorders during the physiotherapeutic routine, and it is known that the abdominal muscle, specially the rectus abdominis muscle, aid the stabilization of the pelvis. Therefore, this paper analyzes the electrical activity of the rectus abdominis muscle in the pelvic retroversion in dorsal decubitus and in orthostatic position and in the lowering of the lower limbs. 30 healthy students, male and female, 17 - 40 yr, divided into two groups--Group 1 : 15 volunteers (pelvic balance); Group 2 (pelvic unbalance) took part in this study. The electrical activity of the right and left supra-umbilical and infra-umbilical portions of the rectus abdominis muscle was detected. The mean RMS values from three attempts from the electromyographic traces were used for the analysis of the electrical activity. The RMS value was submitted to the normalization process. The data were submitted to statistic treatment by the Friedman test, and the analyses of the means and standard deviation towards a level of significance of 95%. The results demonstrated that the portions of the rectus abdominis muscle presented low electrical activity for the groups studied for pelvic retroversion either in dorsal decubitus or and orthostatic position. However, the decreasing movement of the lower limbs towards the portions of the rectus abdominis muscle presented more significant electrical activity whereas the lower portions presented higher activity than the higher ones for Group 2.     

Electromyographic study of the sternocleidomastoid muscle in head movements

The function of the sternocleidomastoid muscle in head movements of 30 young individuals (19-28 years old, both sexes) was studied electromyographically using a TECA TE-4 electromyograph and Beckman surface electrodes. Action potentials were found in the following head movements: free heterolateral rotation; free homolateral inclination; free and counter-resistance protraction; free and counter-resistance flexion and free extension. These movements were performed with the subjects seated and in supine position.     

Ischemic diseases of the lower limbs

On the material of 200 necropsies and 230 surgically amputated lower extremities in patients with an acute obstruction of the main arteries as well as the study of the limb muscles in the appropriate experimental models, the principal rules and the pathogenesis of the muscle damage in the ischemic disease of the lower extremities (IDLE) are described. Four clinico-anatomical variants of the acute IDLE are distinguished: (1) diffuse degenerative-necrotic muscle damage; (2) large-focal necrosis; (3) massive isolated necrosis of single muscles; (4) limb gangrene. Grave general and local somatic background in a patient, causes of death and role of the IDLE in thanatogenesis are characterized.     

不同负荷运动中下肢肌表面肌电图的变化

背景：尝试应用曲线拟合分析方法对表面肌电图进行分析和研究国内外尚处于起步阶段,将其应用于功率自行车运动至疲劳的研究鲜见报道。 目的：探讨功率自行车不同负荷运动中下肢肌中值频率值的变化特征和规律,分析肌肉疲劳拟合曲线的特点及其影响肌肉疲劳的相关因素。 方法：受试者为苏州大学体育学院8名男性青年,利用MONARK功率自行车,对受试者在不同负荷以及不同踏蹬频率下进行测试至疲劳,同时对股直肌、股外侧肌、股内侧肌、胫骨前肌、腓肠肌内侧头和腓肠肌外侧头进行表面肌电信号的采集与记录。分析中值频率指标的变化,并用minitab.15统计软件,按照在F检验的统计学差异有非常显著性意义(P < 0.001)的前提下,选取判定系数R2最大,偏差的平方和最小的原则,对实验结果进行曲线优度拟合。 结果与结论：①功率自行车150 W运动时,肌纤维的募集形式由运动初始快肌纤维募集数量逐渐增多向慢肌纤维募集比例增高转变。②功率自行车300 W运动时,肌纤维的募集形式从运动初期的快肌纤维募集为主逐渐向慢肌纤维募集比例增高转变。③功率自行车150 W运动时,肌肉疲劳的拟合曲线均为三次项曲线,提示影响肌肉疲劳的主要因素有3个。300 W运动时,肌肉疲劳的拟合曲线均为二次项曲线,提示影响肌肉疲劳的主要因素有2个。     

Stimulation-evoked eye movements with and without the lateral rectus muscle pulley

Recent studies have suggested that extraocular muscle (EOM) pulleys, composed of collagen, elastin, and smooth muscle, are among the tissues surrounding the eye. High-resolution magnetic-resonance imaging appears to indicate that the pulleys serve to both constrain and alter the pulling paths of the EOMs. The active pulley hypothesis suggests that the orbital layer of the EOMs inserts on the pulley and serves to control it. Based on anatomical data, the active pulley hypothesis also suggests that the orbital layer does not rotate the eye within the orbit; this is done by the global layer of the muscle. However, no physiological data exist to confirm this hypothesis. Here we used stimulation-evoked eye movements in anesthetized monkeys and cats before and after destruction of the lateral rectus muscle pulley by removal of the lateral bony orbit and adjacent orbital tissue. The absence of these structures resulted in increased lateral, in the primate, and medial, in the cat, eye-movement amplitude and velocity. Vertical eye movements in the cat were not significantly affected. The results indicate that these increases, confined to horizontal eye-movement amplitude and velocity, may be attributed to passive properties within the orbit. In relation to the active pulley hypothesis, we could discern no clear impact (in terms of amplitude or velocity profile of the movements) of lateral eye exposure that could be directly attributable to the active lateral pulley system.     

Electromyographic study of the trapezius muscle in free movements of the arm

The trapezius muscle (superior, middle and inferior portions) was analyzed in 20 volunteers. The electromyographic tests were carried out using a four-channel TECA TE 2-7 electromyograph with surface- and single coaxial needle electrodes. In abduction, adduction and flexion-extension, the 3 portions show increasing and decreasing activity, respectively, from the beginning until the end of these movements. In hyperextension, the 3 portions show increasing activity from the beginning until the end of the movement, with greater participation of the middle portion. Significant differences were not observed in the electromyographic profile of the trapezius, using surface and needle electrodes.     

Preferential coupling between voluntary movements of ipsilateral limbs

Single or cyclical voluntary movements of flexion and extension of the hand, performed in a parasagittal plane, are immediately and naturally coupled with the same movements of the foot only if the extremities follow simultaneously the same direction. Instead, great care and attention are required to move the two segments in opposite directions, an association which tends to reverse spontaneously to the ‘easy’ pattern. This rule is followed independently of the muscles employed, since it holds both when the hand is prone and when it is supine. The same principle also applies to many other couples of voluntary movements of the ipsilateral limbs or of different segments in the same limb.     

Spinal currents in regulation of respiratory movements (Electromyographic study)

Summary Division of the dorsal roots at the level C₅–C₇ caused a transitory reduction of electrical activity of the diaphragm on the same side. Division of the posterior roots of the level T₂–T₈ caused a disappearance or a marked reduction of the activity of the intercostal muscles on that side which was maintained the whole observation period (up to 24 h).Evidently, in respiratory control, besides afferent impulses spreading to the respiratory center via the vagus nerves, other impulses must spread from the respiratory muscles along the posterior roots.(Presented by Active Member AMN SSSR V. V. Parin) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 54, No. 12, pp. 14–17, December, 1962.     

Determination of the optimal parameters maximizing muscle activity of the lower limbs during vertical synchronous whole-body vibration

Purpose

To describe the most effective parameters maximizing muscle activity during whole-body vibration (WBV) exercises on a vertically vibrating (VV) platform.

Methods

The influence of (1) WBV vs. no vibration, (2) vibration frequency (25, 30, 35, 40 Hz), (3) platform peak-to-peak displacement (1.2, 2 mm), and (4) additional loading (no load, 17, 33 kg) on surface electromyographic (sEMG) activity of five lower limb muscles was investigated in eighteen participants.

Results

(1) Comparing WBV to no vibration, sEMG_RMS of the calf muscles was significantly higher with an additional load of 33 kg independently of the displacement and the frequency (P < 0.05). During WBV, (2) muscle activity at 40 Hz WBV was significantly higher than at 25 Hz for the gastrocnemius lateralis (GL) for all loads, and for the vastii medialis and lateralis using the 33 kg load (P < 0.05); (3) sEMG_RMS of all lower limb muscles was significantly increased with the 2 mm compared to the 1.2 mm peak-to-peak displacement (P < 0.05); (4) an effect of additional load was found in the GL, with significantly higher neuromuscular activation for the 33 kg load than no load (P < 0.05).

Conclusions

On a VV platform, we recommend the use of a high platform displacement in combination with a high vibration frequency to provoke the highest muscle activity enhancement. Without maxing out the acceleration stimuli, calf muscles’ sEMG can be enhanced with an additional load of 33 kg which corresponded to 50 % of the body mass.     

Age-related differences in corticospinal excitability and inhibition during coordination of upper and lower limbs

The ability to coordinate upper and lower limbs--a prerequisite for many everyday activities--is known to decline with age. Here we report 2 experiments in which transcranial magnetic stimulation (TMS) was used to assess corticospinal excitatory and inhibitory processes in younger and older adults during cyclical hand-foot movements. In experiment 1, motor evoked potentials (MEP) and silent period (SP) durations were measured from the active right extensor carpi radialis (ECR) muscle while it executed rhythmic oscillations in conjunction with the right or left foot. Younger adults exhibited increased SP with ipsilateral limb combinations and decreased SP with contralateral limb combinations, relative to a baseline hand only condition. Strikingly, older adults exhibited a reduced SP when ipsilateral limbs moved in opposite directions. This effect was found to be most pronounced in those older adults who exhibited poor coordination performance, suggesting that the inability to regulate inhibitory processes may underlie age-related degradation of task performance. Experiment 2 examined motor evoked potentials and SP duration in the left extensor carpi radialis which maintained a tonic contraction while the coordination task was undertaken by the right arm and right or left foot. For younger adults, coordination of ipsilateral limbs was accompanied by increased inhibition in the ipsilateral motor cortex than during the coordination of contralateral limbs. No differences in SP between conditions were noted for the older adults. In summary, older adults' reduced ability to coordinate upper and lower limbs may be related to the capacity to regulate inhibitory function in both hemispheres. This study suggests for the first time a direct link between age-related differences in interlimb coordination and the control of corticospinal inhibitory processes.