Monoarticular Muscles Research Articles

G0200301 一関節筋と二関節筋を基準にした上肢上腕部の機能別実効筋力の計測方法

G0200301 一関節筋と二関節筋を基準にした上肢上腕部の機能別実効筋力の計測方法

LEARNING TO CONTROL THE THREE-LINK MUSCULOSKELETAL ARM USING ACTOR–CRITIC REINFORCEMENT LEARNING ALGORITHM DURING REACHING MOVEMENT

Learning to control the planar three-link musculoskeletal arm by using an Actor–Critic learning algorithm during reaching movements to stationary target is presented. The arm model used in this study includes three skeletal links (hand, forearm and upper arm), three joints (wrist, elbow and shoulder without redundancy) and six nonlinear monoarticular muscles with redundancy which are modeled based on Hill model. The learning system is composed of Actor and Critic parts. For each part, a single layer neural network is used. This learning system applies six activation commands to six muscles at each instant of time. It also uses a reinforcement (reward) feedback for learning process and controlling the arm movement direction. The results showed that with a learning rate α = 0.9 and after 20 episodes, Mean square error (MSE), average reward and average time of reaching the target are gradually converged to the values: 0.0056, 0.02262 and 187 s, respectively. After the 20th episode, the learning will be completed. The research suggests a new direction for designation of learning-based controllers for functional electrical stimulation (FES) applications and for arm movement of autonomous robots.

A Model of Muscle–Tendon Function in Human Walking at Self-Selected Speed

Although joint biomechanics and whole-body energetics are well documented for human walking, the underlying mechanisms that govern individual muscle-tendon behaviors are not fully understood. Here, we present a computational model of human walking that unifies muscle and joint biomechanics with whole-body metabolism for level-ground walking at self-selected speed. In the model, muscle-tendon units that dorsiflex the ankle, and flex and extend the knee, are assumed to act as linear springs upon neural activation; each muscle-tendon is modeled as a tendon spring in series with an isometric force source. To provide the mechanical power lost in step-to-step gait transitions, a Hill-type soleus muscle is modeled to actively plantar flex the ankle using muscle state and force as reflex feedback signals. Finally, to stabilize the trunk during stance, and to protract and retract each leg throughout the swing phase, two mono-articular Hill-type muscles actuate the model's hip joint. Following a forward dynamics optimization procedure, the walking model is shown to predict muscle and joint biomechanics, as well as whole-body metabolism, supporting the idea that the preponderance of leg muscles operate isometrically, affording the relatively high metabolic walking economy of humans.

Electromyographic Amplitude vs. Concentric and Eccentric Squat Force Relationships for Monoarticular and Biarticular Thigh Muscles

This study examined the linearity of the electromyographic (EMG) amplitude vs. concentric and eccentric squat force relationships for monoarticular and biarticular thigh muscles. Fourteen resistance-trained men (mean age ± SD: 22 ± 2 years; estimated thigh muscle cross-sectional area: 221.9 ± 22.7 cm) performed concentric and eccentric squats using a novel testing device from 10 to 90% of their maximum average force. Surface EMG signals were detected from the right vastus lateralis, rectus femoris, and biceps femoris. Linear regression was used to examine the relationships between EMG amplitude and force, and repeated measures analyses of variance were used to assess differences among the muscles. Moderate-to-high coefficients of determination were found for the vastus lateralis for both concentric and eccentric testings (r = 0.587-0.992). For the biceps femoris, the mean linear slope coefficient was significantly greater for concentric vs. eccentric testing (0.044 vs. 0.013 μV RMS·N; p = 0.002; effect size = 1.44). Although EMG amplitude for the vastus lateralis and rectus femoris increased with changes in eccentric force output, the electrical activity of the biceps femoris remained stable. These results demonstrated that the EMG amplitude vs. force relationships for the vastus lateralis were linear, despite the fact that force production during the squat is related to the activation of muscles that must simultaneously function as agonists and antagonists. Our findings for eccentric force testing are in agreement with investigations showing reduced hip extensor activity during concurrent extension at the hip and knee joints.

Muscle force distribution for adaptive control of a humanoid robot arm with redundant bi-articular and mono-articular muscle mechanism

Robot arms driven by bi-articular and mono-articular muscles have numerous advantages. If one muscle is broken, the functionality of the arm is not influenced. In addition, each joint torque is distributed to numerous muscles, and thus the load of each muscle can be relatively small. This paper addresses the problem of muscle control for this kind of robot arm. A relatively mature control method (i.e. sliding mode control) was chosen to get joint torque first and then the joint torque was distributed to muscle forces. The muscle force was computed based on a Jacobian matrix between joint torque space and muscle force space. In addition, internal forces were used to optimize the computed muscle forces in the following manner: not only to make sure that each muscle force is in its force boundary, but also to make the muscles work in the middle of their working range, which is considered best in terms of fatigue. Besides, all the dynamic parameters were updated in real-time. Compared with previous work, a novel method was proposed to use prediction error to accelerate the convergence speed of parameter. We empirically evaluated our method for the case of bending-stretching movements. The results clearly illustrate the effectiveness of our method towards achieving the desired kinetic as well as load distribution characteristics.

APPLICATION OF AN EVOLUTIONARY ACTOR–CRITIC REINFORCEMENT LEARNING METHOD FOR THE CONTROL OF A THREE-LINK MUSCULOSKELETAL ARM DURING A REACHING MOVEMENT

In this paper, the control of a planar three-link musculoskeletal arm by using a revolutionary actor–critic reinforcement learning (RL) method during a reaching movement to a stationary target is presented. The arm model used in this study included three skeletal links (wrist, forearm, and upper arm), three joints (wrist, elbow, and shoulder without redundancy), and six non-linear monoarticular muscles (with redundancy), which were based on the Hill model. The learning control system was composed of actor, critic, and genetic algorithm (GA) parts. Two single-layer neural networks were used for each part of the actor and critic. This learning control system was used to apply six activation commands to six monoarticular muscles at each instant of time. It also used a reinforcement (reward) feedback for the learning process and controlling the direction of arm movement. Also, the GA was implemented to select the best learning rates for actor–critic neural networks. The results showed that mean square error (MSE) and average episode time gradually decrease and average reward gradually increases to constant values during the learning of the control policy. Furthermore, when learning was complete, optimal values of learning rates were selected.

Hopping by a Monopedal Robot with a Biarticular Muscle by Compliance Control – An Application of an Electromagnetic Linear Actuator –

The compliance of muscles with external force and the structural stability given by biarticular muscles are important features of animals for realizing dynamic whole-body motion such as running and hopping in various environments. For this reason, we have been studying an electromagnetic linear actuator. This actuator emulates the behavior of a human muscle, such as spring-damper properties, through the quick control of output force, i.e., impedance control. It is expected to be used as an artificial muscle. In this paper, we design a monopedal robot possessing bi- and mono-articular muscles implemented by linear actuators. Thanks to the biarticular muscle, the direction of bouncing by a robot can be controlled by changing the stiffness ellipse at the endpoint, i.e., foot, of the robot. We make a simulator of the robot to evaluate dynamic characteristics and show that the robot hops stably by adjusting the stiffness ellipse. We also confirm that the behavior of the real robot is consistent with that of our simulator.

Long-term effects after conversion of biarticular to monoarticular muscles compared with musculotendinous lengthening in children with spastic diplegia

Adverse effects such as increased anterior pelvic tilt (APT) are reported after muscle-tendon lengthening (MTL) for the correction of flexed knee gait in cerebral palsy. The conversion of biarticular muscles (CBM) to monoarticular muscles represents an alternative treatment, but only few short-term results have been published, without comparison with MTL. The long-term outcome of 21 diplegic patients treated with CBM in a prospective study was compared with the results in MTL patients in a matched-pair analysis. Standardized clinical examination and three-dimensional gait analysis were done before surgery, 1 year thereafter, and at long-term follow-up a mean of 9.2 years postoperatively. Mean APT increased one year after surgery in both groups. This increase was higher in MTL patients and statistically significant only for this group. Knee flexion at initial contact and minimum knee flexion in stance were significantly decreased in both groups, while in swing the CBM group tended to show more of a decrease in knee flexion but at the cost of reduced peak flexion. Both groups showed deterioration of kinematic knee parameters through to long-term follow-up; the favourable effects of CBM disappeared, and the two groups displayed comparable average pelvic and knee kinematics. Considering individual patterns the prevalence of increased APT was lower in the CBM group 1 year after surgery, indicating that sparing the semitendinosus may have a positive effect on pelvic stability. However, after 9 years 30% of the patients in both groups showed increased APT indicative of persistent hamstring insufficiency. These results demonstrate that CBM, a significantly more extensive procedure, has no long-term advantage over MTL.

Fusimotor control of spindle sensitivity regulates central and peripheral coding of joint angles.

Proprioceptive afferents from muscle spindles encode information about peripheral joint movements for the central nervous system (CNS). The sensitivity of muscle spindle is nonlinearly dependent on the activation of gamma (γ) motoneurons in the spinal cord that receives inputs from the motor cortex. How fusimotor control of spindle sensitivity affects proprioceptive coding of joint position is not clear. Furthermore, what information is carried in the fusimotor signal from the motor cortex to the muscle spindle is largely unknown. In this study, we addressed the issue of communication between the central and peripheral sensorimotor systems using a computational approach based on the virtual arm (VA) model. In simulation experiments within the operational range of joint movements, the gamma static commands (γs) to the spindles of both mono-articular and bi-articular muscles were hypothesized (1) to remain constant, (2) to be modulated with joint angles linearly, and (3) to be modulated with joint angles nonlinearly. Simulation results revealed a nonlinear landscape of Ia afferent with respect to both γs activation and joint angle. Among the three hypotheses, the constant and linear strategies did not yield Ia responses that matched the experimental data, and therefore, were rejected as plausible strategies of spindle sensitivity control. However, if γs commands were quadratically modulated with joint angles, a robust linear relation between Ia afferents and joint angles could be obtained in both mono-articular and bi-articular muscles. With the quadratic strategy of spindle sensitivity control, γs commands may serve as the CNS outputs that inform the periphery of central coding of joint angles. The results suggest that the information of joint angles may be communicated between the CNS and muscles via the descending γs efferent and Ia afferent signals.

IS IT NECESSARY TO INCLUDE BIARTICULAR EFFECTS WITHIN JOINT TORQUE REPRESENTATIONS OF KNEE FLEXION AND KNEE EXTENSION?

The purpose of this study was to consider whether it is necessary for biarticular effects to be accounted for in subject-specific representations of maximal voluntary knee extension and knee flexion torques. Isovelocity and isometric knee torques were measured on a single participant at three different hip angles using a Contrex MJ dynamometer. Maximal voluntary torque was represented by a 19-parameter two-joint function of knee and hip joint angles and angular velocities with the parameters determined by minimising a weighted root mean square difference between measured torques and the two-joint function. The weighted root mean square difference between the two-joint function and the measured knee flexion torques was 14 Nm or 9% of maximum torque, whilst for knee extension the difference was 26 Nm or 9% of maximum torque. The two-joint representation was shown to be more accurate than an existing single-joint representation for torques measured at hip angles other than those used to derive the single-joint function parameter values. The differences between the traditionally used single-joint representation and the measured knee flexion and knee extension torques were largest for the most extended hip joint angle (15% and 18% of maximum torque respectively) while the corresponding differences for the two-joint function were 9% and 8% of maximum torque. It is concluded that a two-joint function can account for changes in knee flexion and knee extension joint torques due to both monoarticular and biarticular muscles over a range of both hip and knee angles, and this has the potential to improve the biofidelity of whole body subject-specific torque-driven simulation models.

一関節筋と二関節筋の協調による四肢の力出力分布特性

一関節筋と二関節筋の協調による四肢の力出力分布特性

二関節筋と運動制御

Recently the unique functional characteristics of bi-articular muscles have been revealed by means of EMG kinesiological analysis and control engineering analysis. A two-joint limb link mechanism provided with one antagonistic pair of bi-articular muscles passing over two adjacent joints as well as two antagonistic pairs of mono-articular muscles at both end joints could control output forces exerted at the end point of the link mechanism in an arbitral direction with only a single input command signal informing the desired direction. The output force distribution of the limb link mechanism with three pairs of six muscles showed a hexagonal shape, whereas the link mechanism without the paired bi-articular muscles and only with the two pairs of mono-articular muscles showed a tetragonal shape. Configurational characteristics of the hexagonal output force distribution indicated that an individual functionally different effective muscular strength can be evaluated from the output force values of four designated points on the output force distribution line. Such a limb link mechanism could also dissolve contact tasks in order to maintain postural stability. Clinical applications utilizing the unique control properties of bi- articular muscles may shed light on future rehabilitation medicine therapies.

Bilateral deficit in power production during multi-joint leg extensions

The purpose of this study was to determine the presence of the bilateral deficit both as a function of overall and individual joint power. Most studies addressing the deficit have assessed force; however, in most sporting events maximal power is more important than maximal force production. To address this, in the current study we assessed the bilateral deficit for multi-joint movements as measured by overall lower extremity and individual joint power. We assessed power production using an isokinetic machine permitting both unilateral and bilateral leg extensions. Several significant effects and interactions between the contraction type (unilateral, bilateral, alternating unilateral), side of the body, lower extremity joint, and percentage of a 1-RM load were revealed. All interactions were between the lower extremity joints (hip, knee, ankle) and involved the contraction protocol (P=0.001), the percentage of 1-RM load (P=0.0002), and the side of the body (P=0.0003). Taken together, the results indicate that the bilateral deficit is manifested using a measure of power, but more importantly, the deficit has differential implications based on the overall resistance, and various joints involved in the movement. In conclusion, a reduction in power generation was evidenced for both simultaneous contractions of the leg extensors as well as reciprocal contractions. With reduced contributions from the knee joint during bilateral and reciprocal contractions, combined with past research demonstrating differential activation of mono-articular knee joint muscles, evidence for reduced contributions from the peripheral nervous system are suggested based on the results of this study.

Abnormal coactivation of knee and ankle extensors is related to changes in heteronymous spinal pathways after stroke

BackgroundAbnormal coactivation of leg extensors is often observed on the paretic side of stroke patients while they attempt to move. The mechanisms underlying this coactivation are not well understood. This study (1) compares the coactivation of leg extensors during static contractions in stroke and healthy individuals, and (2) assesses whether this coactivation is related to changes in intersegmental pathways between quadriceps and soleus (Sol) muscles after stroke.MethodsThirteen stroke patients and ten healthy individuals participated in the study. Levels of coactivation of knee extensors and ankle extensors were measured in sitting position, during two tasks: maximal isometric voluntary contractions in knee extension and in plantarflexion. The early facilitation and later inhibition of soleus voluntary EMG evoked by femoral nerve stimulation were assessed in the paretic leg of stroke participants and in one leg of healthy participants.ResultsCoactivation levels of ankle extensors (mean ± SEM: 56 ± 7% of Sol EMG max) and of knee extensors (52 ± 10% of vastus lateralis (VL) EMG max) during the knee extension and the ankle extension tasks respectively were significantly higher in the paretic leg of stroke participants than in healthy participants (26 ± 5% of Sol EMG max and 10 ± 3% of VL EMG max, respectively). Early heteronymous facilitation of Sol voluntary EMG in stroke participants (340 ± 62% of Sol unconditioned EMG) was significantly higher than in healthy participants (98 ± 34%). The later inhibition observed in all control participants was decreased in the paretic leg. Levels of coactivation of ankle extensors during the knee extension task were significantly correlated with both the increased facilitation (Pearson r = 0.59) and the reduced inhibition (r = 0.56) in the paretic leg. Measures of motor impairment were more consistently correlated with the levels of coactivation of biarticular muscles than those of monoarticular muscles.ConclusionThese results suggest that the heteronymous pathways linking quadriceps to soleus may participate in the abnormal coactivation of knee and ankle extensors on the paretic side of stroke patients. The motor impairment of the paretic leg is strongly associated with the abnormal coactivation of biarticular muscles.

Rectus abdominis muscle injuries in elite handball players: management and rehabilitation.

Muscle injuries generally occur in two-joint muscles with a high percentage of type II fibers during the performance of eccentric activity. Some muscle injuries, such as those located in the adductor longus, a monoarticular muscle, as well as rectus abdominis do not fully comply with these requirements. This study examines five cases of elite handball players with ruptured rectus abdominals. Sonographically, lesions in rectus abdominis are shown as a disruption of the fibrillar pattern with a hematic suffusion that invades the entire lesion. In some of the cases, the ultrasound study was complemented with a MRI. A unified rehabilitation protocol was applied and the return to play time of each handball player ranged between 16 and 22 days, with an average of 18.2 days. Follow-up at 15 months showed no evidence of re-injury or residual discomfort and all of them are playing at their highest level. The aim of this study was to illustrate a feature of handball injury that, as in tennis and volleyball, is uncommon and so far has not been specifically reported. The phenomenon of contralateral abdominal hypertrophy in handball appears in the dominant arm as in tennis and volleyball.

Neuromuscular Activation Of Vastus Intermedius Muscle During Isometric Knee Flexion At Different Knee Joint Angles

Activation pattern of vastus intermedius (VI), which locates at deeper region of the quadriceps femoris (QF), is poorly understood during extension as well as flexion of the knee joint in humans. Montgomery et al. (1994) found that electromyographic (EMG) signal by insertion of a wire electrode directly to VI reached to 20% of maximum effort of knee extension in the initial swing phase of running. They suggested that activation of VI could control knee flexion of the knee joint in running. PURPOSE: The purpose of this study is to investigate activity of VI during isometric knee flexion using a newly developed technique to record surface EMG activity of VI (Watanabe and Akima 2009). The main hypothesis was that the VI would activate during isometric contraction of the knee flexion. METHODS: Ten healthy men (24.2±8.1 years old, 174.7±5.9 cm, 67.4±12.5 kg) performed 25%, 50%, 75% and 100% of maximal voluntary contraction (MVC) of knee flexion at 90°, 120° and 150° of knee joint angles (180° = fully extended). Surface EMG of four individual muscles, i.e. VI, vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) of the QF was recorded using the same technique to our previous studies (Watanabe & Akima 2009, 2010). Ultrasonography was used to identify the superficial region of VI for placement of a surface EMG electrode. Root mean square (RMS) of individual muscles of QF was normalized by RMS of MVC during isometric knee extension. RESULTS: At three tested knee joint angles, normalized RMS of VI was significantly higher than that of VL, VM and RF at all force levels (all p<0.05). Comparison of MVC among three different knee joint angles, normalized RMS of VI at 150° (63.0±29.7%) was significantly higher than that of 90° (29.2±19.3%) and 120° (40.4±22.7%) of knee joint angle. Overall, the highest RMS of VI was found at 150° and the lowest RMS of VI was found at 90° when comparing with the same force levels. CONCLUSIONS: An important evidence of this study is that surprisingly higher activation was found in VI, which is well known as a monoarticular muscle of knee extension, during isometric "knee flexion", and that the degree of action of VI was increased with extension of the knee joint. These results suggest that VI may contribute somehow to isometric knee flexion exercise.

2P2-I04 Mckibben型アクチュエータによる4自由度倒立振子モデルの姿勢制御 : 第1報:アクチュエータの特性実験及び倒立振子モデルの設計(ヒューマノイド)

The redundancy of human musculoskeletal system, caused by bi-articular muscles, is one of the research topics to describe such as the functional roles of the bi-articular muscles, the application for the industrial machines. In order to reveal these questions, esecially for the functional roles of bi-articular muscles in lower limb during upright standing in humans, we developed the four degree-of-freedom (DOF) inverted pendulum model. We used nine pneumatic artificial muscles (PAMs), 4/9 actuators were for the bi-articular muscles and the others as mono-articular muscles. In this paper, we demonstrated the relationships between length, load and time constant as the static characteristics of the PAMs. Last part of this paper, we described the concepts and designs of our four-DOF model..

J102032 高齢者や介護者を対象とするこ関節筋構造パワーアシスト機構の研究([J10203]ライフサポート(3))

This research is the Power Assist Suite for senior citizens and helpers that look ahead to the future being an aging society with fewer children. The most Power Assist Suits developed now have actuators to act only on each joint like the actuator acting only on the joint of knee can't act on another joint. However, the muscular arrangement of the human body has already been known, and Humans have the muscles that operate two joints adjoined (bi-articular muscles) in addition to the muscles that operate one joint (mono-articular muscles) , and bi-articular muscles gives the holding power of extremities the very important effect. We have researched the Power Assist Mechanism using bi-articular muscles structure focusing this characteristic.

Simulation study of the importance of biarticular muscles on human vertical jump performance

The aim of this study was to quantify the importance of biarticular muscles on vertical squat jump. In order to do that, we used a neuromusculoskeletal model and a forward dynamics computer simulation. In separate trials biarticular muscles were removed from the neuromusculoskeletal model, firstly only one muscle was removed each trial, and then all three biarticular muscles were removed together in one more trial. Investigated were three main groups of biarticular muscles of lower extremities: m. rectus femoris, hamstrings and m. gastrocemius. The results demonstrated that monoarticular muscles are primary producers of the force used to accelerate the body’s centre of gravity vertically. While the function of biarticular muscles is twofold: Therefore, we conclude that the most important function of biarticular muscles in a vertical jump is to help to coordinate jump movement and increase the effectiveness of the usage of muscle force to accelerate vertically the body’s centre of gravity.

遊星歯車二関節駆動アームのモータ配置と出力特性

In conventional robot arms, one motor is placed to one joint. The human upper extremities can be simplified into three antagonistic pairs of muscles, those which are a pair of shoulder mono-articular muscles, a pair of elbow mono-articular and a pair of elbow/shoulder bi-articular muscles. In the present study, it is assumed that the bi-articular muscles have a profound effect on not only the position control but power output and rigidity of the arm tip. This study reports that the system is able to imitate the function of bi-article muscles in human uppers by using rotary motors and a planetary gear.