Multiarticular Muscles Research Articles

Short-Term Effects of Muscular Denervation and Fasciotomy on Global Limb Variables during Locomotion in the Decerebrate Cat

The motor system is capable of preserving the trajectories during locomotion of task level variables such as limb length and limb orientation in the face of paralysis of major muscle groups. This compensation is accomplished by the adjustment of the kinematics of joints other than the one most affected by the paralysis. The conservation of these task level variables could be accomplished quickly by feedback regulation or intrinsic mechanics, or by a longer-term adaptive process. We investigated the immediate effects of denervation of the triceps surae muscles in one limb of stepping, decerebrate cats to determine whether task level variables were preserved by short-term regulatory or intrinsic mechanisms. We further investigated the effects of disruption of the crural fascia in conjunction with denervation of the triceps surae muscles to determine whether the system consisting of multi-articular muscles of the thigh and crural fascia provided some contribution toward the preservation of limb length and orientation. Denervation led to substantial increases in ankle yield during stance, as previously observed, but also to significant decreases in limb length during early stance. Disruption of the crural fascia did not lead to increased ankle yield but, instead, to evidence for decreased propulsion. The results suggest that the preservation of task level variables observed in other studies does not result from online error correction or intrinsic properties of the musculoskeletal system but, by inference, from longer-term neural adaptation.

1P1-O12 高効率推進を可能とする多関節ヘビ型ロボットの自律分散制御則(バイオロボティクス)

The mechanism of multi-articular muscles that contributes to the emergence of animal behavior has not been clarified thus far. To address this issue, we focus on the slithering motion of snakes, which have numerous antagonistic muscle-tendon chains that span several tens of vertebrae. From theoretical analyses on the basis of the continum model, the acceleration of the body in the longitudinal direction is found to be proportional to the number of segments spanned by each muscle. On the basis of this theoretical result, we propose a decentralized control scheme for the efficient locomotion of a multi-articular serpentine robot. We conduct simulations using this control scheme, and the results show that the locomotion efficiency increases as the number of segments spanned by each muscle increases.

Modeling of Multiarticular Muscles: Importance of Inclusion of Tendon–Pulley Interactions in the Finger

The purpose of this study was to examine force transmission from one of the major multiarticular muscles of the finger, flexor digitorum profundus (FDP), to the index finger. Specifically, we examined whether the popular moment arm (MA)-joint torque technique of modeling muscle force transmission can accurately represent the effects of the FDP on finger movement. A dynamic finger model employing geometric MA values (model I) was compared with another model including realistic tendon force transformation mechanisms via pulley structures and joint reaction forces (model II). Finger flexion movements generated by these models were compared with those obtained from in vivo stimulation experiments. The model with the force transformation mechanisms (model II) resulted in more realistic joint spatial coordination (i.e., proximal interphalangeal > metacarpophalangeal > or = distal interphalangeal) than the MA-based model (model I) in relation to the movement patterns evoked by stimulation. Also, the importance of the pulley structures and passive joint characteristics was confirmed in the model simulation; altering/eliminating these components significantly changed the spatial coordination of the joint angles during the resulting movements. The results of this study emphasize the functional importance of the force transformation through various biomechanical components, and suggest the importance of including these components when investigating finger motor control, such as for examining injury mechanisms or designing rehabilitation protocols.

Evidence of isometric function of the flexor hallucis longus muscle in normal gait

Studying mechanics of the muscles spanning multiple joints provides insights into intersegmental dynamics and movement coordination. Multiarticular muscles are thought to function at “near-isometric” lengths to transfer mechanical energy between the adjacent body segments. Flexor hallucis longus (FHL) is a multiarticular flexor of the great toe; however, its potential isometric function has received little attention. We used a robotic loading apparatus to investigate FHL mechanics during simulated walking in cadaver feet, and hypothesized that physiological force transmission across the foot can occur with isometric FHL function. The extrinsic foot tendons, stripped of the muscle fibers, were connected to computer-controlled linear actuators. The FHL activity was controlled using force-feedback (FC) based upon electromyographic data from healthy subjects, and subsequently, isometric positional feedback (PC), maintaining the FHL myotendinous junction stationary during simulated walking. Tendon forces and excursions were recorded, as were the strains within the first metatarsal. Forces in the metatarsal and metatarsophalangeal joint were derived from these strains. The FHL tendon excursion under FC was 6.57±3.13 mm. The forces generated in the FHL tendon, metatarsal and metatarsophalangeal joint with the FHL under isometric PC were not significantly different in pattern from FC. These observations provide evidence that physiological forces could be generated along the great toe with isometric FHL function. A length servo mechanism such as the stretch reflex could likely control the isometric FHL function during in vivo locomotion; this could have interesting implications regarding the conditions of impaired stretch reflex such as spastic paresis and peripheral neuropathies.

2A1-B11 可変弾性要素を介した制御系と機構系の有機的連関 : 2次元ヘビ型ロボットを用いた事例研究(移動知)

This study is intended to intensively discuss how control and mechanical systems should be coupled by taking a 2D serpentine robot consisting of multiple body segments as a case study. In order to realize "well-balanced" coupling between control and mechanical systems, we have investigated the role of multiarticular muscles, which specify the long-distance correlation between the body segments, in the generation of behavior. Preliminary simulation results indicate that a certain degree of long-distance correlation derived from the multiarticular muscles enhances the adaptability and the controllability without sophisticated sensory feedback mechanisms. We expect that this "embodied" intelligence allows us to significantly reduce the complexity of control systems.

Impact of finger posture on mapping from muscle activation to joint torque

The mapping from muscle activation to joint torque production can be difficult to determine for the multi-articular muscles of the fingers. This relationship was examined in vivo as a function of posture in the index finger. Five healthy adults participated in an experiment in which the seven muscles of the index finger were sequentially electrically stimulated using intramuscular electrodes. Each muscle was stimulated at 12 different finger postures consisting of specified flexion of the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints, while fingertip forces and moments were recorded. Repeated measures analysis of variance revealed that joint torques resulting from the stimulation were significantly dependent upon finger posture (p < 0.05). The magnitude of the change in joint torque across postures was generally greater than 60%. This value is much larger than the difference attributable to the increase in active muscle force that occurs at longer muscle length, in accordance with the force-length curve (10-20% for the estimated length changes). In addition, the relative distribution of the joint torques generated by a given muscle activation was dependent upon finger posture for the intrinsic muscles and the long finger flexors (p < 0.05); the ratio of one joint torque to another varied with posture for these muscles, in some cases by more than 50%. Joint torque is a product of both muscle force and the corresponding moment arm. As the change in active muscle force was limited, these data suggest that substantial changes in muscle moment arms occur with posture. Therefore, this postural dependence should be considered when constructing biomechanical models of the hand or planning tendon transfers for the fingers.

Multi-functionality of the cat medical gastrocnemius during locomotion

The functional role of biarticular muscles was investigated based on direct force measurement in the cat medial gastrocnemius (MG) and analysis of hindlimb kinematics and kinetics for the stance phase of level, uphill, and downhill walking. Four primary functional roles of biarticular muscles have been proposed in the past. These functional roles have typically been discussed independently of each other, and biarticular muscles have rarely been assigned more than one functional roles for different phases of the work cycle. The purpose of this study was to elucidate the functional role of the biarticular cat MG during locomotion. It was found that MG forces were primarily associated with the moment requirements at the ankle for most of the stance phase, but also helped to satisfy the moments at the knee in the initial phase of stance. In the second half of stance, MG transferred mechanical energy from the knee to the ankle from the knee to the ankle, while simultaneously producing a substantial amount of mechanical work. Based on these results, we hypothesize that MG's primary function is that of an ankle extensor. However, because of the coupling of the ankle extensor moment with a knee flexor moment in the initial, and a knee extensor moment in the final phase of stance, MG satisfies two joint moments in early stance, and transfers mechanical energy from the knee to the ankle in late stance. We conclude that cat MG has multiple functional roles during the stance phase of locomotion, and speculate that such multi-functionality also exists in other bi- and multi-articular muscles.

An integrative approach to the biomechanical function and neuromuscular control of the fingers

The exquisite mechanical functionality and versatility of the human hand emerges from complex neuro–musculo–skeletal interactions that are not completely understood. I have found it useful to work within a theoretical/experimental paradigm that outlines the fundamental neuro–musculo–skeletal components and their interactions. In this integrative paradigm, the laws of mechanics, the specifications of the manipulation task, and the sensorimotor signals define the interactions among hand anatomy, the nervous system, and manipulation function. Thus, our collaborative research activities emphasize a firm grounding in the mechanics of finger function, insistence on anatomical detail, and meticulous characterization of muscle activity. This overview of our work on precision pinch (i.e., the ability to produce and control fingertip forces) presents some of our findings around three Research Themes: Mechanics-based quantification of manipulation ability; Anatomically realistic musculoskeletal finger models; and Neural control of finger muscles. I conclude that (i) driving the fingers to some limit of sensorimotor performance is instrumental to elucidating motor control strategies; (ii) that the cross-over of tendons from flexors to extensors in the extensor mechanism is needed to produce force in every direction, and (iii) the anatomical routing of multiarticular muscles makes co-contraction unavoidable for many tasks. Moreover, creating realistic and clinically useful finger models still requires developing new computational means to simulate the viscoelastic tendinous networks of the extensor mechanism, and the muscle–bone–ligament interactions in complex articulations. Building upon this neuromuscular biomechanics paradigm is of immense clinical relevance: it will be instrumental to the development of clinical treatments to preserve and restore manual ability in people suffering from neurological and orthopedic conditions. This understanding will also advance the design and control of robotic hands whose performance lags far behind that of their biological counterparts.

Simulated feedforward neural network coordination of hand grasp and wrist angle in a neuroprosthesis.

This study presents a possible solution of the general problem of coordinating muscle stimulation in a neuroprosthesis when multiarticular muscles introduce mechanical coupling between joints. In a hand-grasp neuroprosthesis, extrinsic hand muscles cross the wrist joint and introduce large wrist flexion moments during grasp. In order to control hand grasp and wrist angle independently, a controller must take the mechanical coupling into account. In simulation, we investigated the use of artificial neural networks to coordinate hand and wrist muscle stimulation. The networks were trained with data that is easily obtained experimentally. Feedforward control showed excellent hand and wrist coordination when the properties of the system were fixed and there were known external loads. Predictable disturbances (e.g., gravity acting on the hand) can be compensated by sensing arm orientation. However, since wrist angle is sensitive to unpredictable disturbances (e.g., fatigue or object weight), voluntary intervention or feedback control may be required to reduce residual errors.

Electromyography of shoulder muscles in relation to force direction

In a static force task the electromyographic level of 14 shoulder muscles including 3 rotator cuff muscles was related to force direction. Surface and wire electrodes were used. The force direction of maximal electromyography (principal action) was identified for every muscle. The principal action expresses the function of a muscle in a specific situation. The deltoid was active in a force direction that could be understood from its anatomy. The trapezius and serratus were mainly involved in stabilizing the scapula in upward and outward force directions. Large multiarticular muscles such as the pectoralis and the latissimus were active in downward and forward forces. The rotator cuff seems to have a specific role in stabilizing the glenohumeral joint. These data can be compared with data of patients with shoulder disorders and with kinematic data of a shoulder model.

What can we expect from models of motor control?

AbstractThe lambda model of servocontrol seems superior to the alpha model in terms of dealing with the mechanical complexities of nonlinear and multiarticular muscles. Both, however, can be trivialized by noting that the “control variable” may simply be the sum of descending influences at propriospinal interneurons in the case of the lambda model or in the muscles themselves in the case of the alpha model. The notion that the brain explicitly computes output in terms of any such control variables may be an engineering metaphor, useful for conceptual understanding but not for generating predictive hypotheses about higher motor circuitry.

Coordination of multiple muscles in two degree of freedom elbow movements.

The present study quantifies electromyographic (EMG) magnitude, timing, and duration in one and two degree of freedom elbow movements involving combinations of flexion-extension and pronation-supination. The aim is to understand the organization of commands subserving motion in individual and multiple degrees of freedom. The muscles tested in this study fell into two categories with respect to agonist burst magnitude: those whose burst magnitude varied with motion in a second degree of freedom at the elbow, and those whose burst magnitude depended on motion in one degree of freedom only. In multiarticular muscles contributing to motion in two degrees of freedom at the elbow, we found that the magnitude of the agonist burst was greatest for movements in which a muscle acted as agonist in both degrees of freedom. The burst magnitudes for one degree of freedom movements were, in turn, greater than for movements in which the muscle was agonist in one degree of freedom and antagonist in the other. It was also found that, for movements in which a muscle acted as agonist in two degrees of freedom, the burst magnitude was, in the majority of cases, not different from the sum of the burst magnitudes in the component movements. When differences occurred, the burst magnitude for the combined movement was greater than the sum of the components. Other measures of EMG activity such as burst onset time and duration were not found to vary in a systematic manner with motion in these two degrees of freedom. It was also seen that several muscles which produced motion in one degree of freedom at the elbow, including triceps brachii (long head), triceps brachii (lateral head), and pronator quadratus displayed first agonist bursts whose magnitude did not vary with motion in a second degree of freedom. However, for the monoarticular elbow flexors brachialis and brachioradialis, agonist burst magnitude was affected by pronation or supination. Lastly, it was observed that during elbow movements in which muscles acted as agonist in one degree of freedom and antagonist in the other, the muscle activity often displayed both agonist and antagonist components in the same movement. It was found that, for pronator teres and biceps brachii, the timing of the bursts was such that there was activity in these muscles concurrent with activity in both pure agonists and pure antagonists.(ABSTRACT TRUNCATED AT 400 WORDS)

The computation of position sense from spindles in mono- and multiarticular muscles

It is known that muscle spindles provide the majority of information about limb position, but little is known about how position sense is computed from their signals. We have developed a family of musculoskeletal models in order to determine some of the fundamental properties associated with transforming noisy spindle information into putative internal coordinate frames for position sense. A two-joint model was developed containing one biarticular and two monoarticular muscles with a total of 1000 sensors distributed among them. The sensors were assumed to function like spindle secondary afferents under fusimotor control designed to optimize their ability to encode static position in the presence of constant output noise. The optimal distribution of sensors was found to depend strongly on the coordinate frame in which position was measured (intersegmental angle, segment orientation, or end-point of the limb) and on the topology of the biarticular muscle with respect to the plane of motion. A similar analysis was performed for an anthropometric model of the human arm, using previously published counts of muscle spindles. In general, the actual distribution of spindles about the elbow and shoulder does not seem to favor any single coordinate frame for position sense. We also looked at the potential accuracy in detecting changes in joint angles based on the distribution of muscle spindles throughout the human body. The distribution of spindles about individual joints accounts well for psychophysical data showing a proximodistal descending gradient of angular resolution that partially reflects the relative importance of more proximal joints for determining the location of the end-point.

Architectural features of multiarticular muscles

Most of the available information on neuromuscular organization and musculoskeletal mechanics comes from a few muscles that physiologists choose to study because they are relatively simple. They usually cross a single hinge joint, have a single band of innervation, and are composed of muscle fibres with similar lengths, all acting in parallel. In most species, such muscles are in the minority. In order to develop quantitative models of complete musculoskeletal systems, it is necessary also to study the less simple muscles. This has revealed several types of architecture that were somewhat unexpected and may have important functional consequences. Limb muscles that span more than one joint are often quite long and must withstand large length changes; their parallel fascicles often contain multiple, relatively short fibres interdigitated in-series. Axial muscles often span many joints and are composed of in-series compartments. A variety of neuromuscular architectures seems to have evolved to deal with problems of mechanical instability arising from imbalances of force between fibres, motor units and compartments. These may be prone to particular failure modes in response to athletic strain, dystrophic diseases, and functional electrical stimulation.

What Is a Joint Torque for Joints Spanned by Multiarticular Muscles?

What Is a Joint Torque for Joints Spanned by Multiarticular Muscles?

Development of Motor Patterns in Cervical Muscles of Drinking Chickens

Motor patterns of the cervical muscles are decuced by calculating changes in muscle length, and changes in torque of the vertebral joints from the cervical motion patterns measured from films of the upstroke phase of drinking chickens. These calculated motor patterns correspond well with recorded electromyograms (EMG) in 5 adult chickens for nearby and far away positioned waterboxes. It is concluded that under the conditions of the drinking upstroke changes in muscle length and increasing or high torque values primarily determine motor patterning in cervical muscles. It is shown that in adult chicken the long dorsal muscles (M. biventer cervicis and the far cranially running slips of M. longus colli dorsalis), the MM. cervicales ascendentes and M. complexus must contribute in elevating head and neck. By calculating changes in muscle length and torques during the upstroke of unrestrained hatchlings, four weeks old, and adult chichens it is investigated whether the motor patterns are expected to change during ontogeny. Calculations show that motor patterns must change due to the growth pattern of the cervical system. In the younger stages head and neck are elevated mainly by shortening of only M. biventer and the slip of M. longus colli dorsalis running from notarium to axis. Shorthening of these muscles causes rotations in the cervical joints according with a specific motion pattern (bike chain). A mechanical model illustrates that action of these long, multi-articular muscles must result in that unique pattern. In adults, however, the torques are so large that other muscles (MM. cervicales ascendentes) must become active as well. This results in a change in the kinematic pattern. Finally, it is explained what parallel relationship exists between this transition in head-neck motion and a change in ratio of mouth volume and mouth wall surface. That change in ratio requires a transition in head-neck motion to ensure that water stays in the beak during head elevation in adult chicken. That transition is similar to the transition in head-neck motion that follows from the growth pattern of the cervical column.

Combined Flexor and Extensor Release for Activation of Voluntary Movement of the Fingers in Patients With Cerebral Palsy

Twenty deformed hands of 19 Japanese patients with cerebral palsy were treated with release of the flexor digitorum profundus, the flexor digitorum sublimis, and the extensor digitorum communis. The results were satisfactory and included enhanced daily activities, voluntary grasp, and release of the fingers. Simultaneous cocontraction of the multiarticular muscles inhibits voluntary movement of the fingers and causes rigidity and involuntary movements. Use of the intrinsic muscles is facilitated by reducing hypertonicity of the multiarticular muscles and by activation of voluntary movements of the fingers. Many such patients can then become functionally independent.

Spinal cord circuits: are they mirrors of musculoskeletal mechanics?

Over the past decade, research at three different levels of sensorimotor control has revealed a degree of complexity that challenges traditional hypotheses regarding servocontrol of individual muscles: (a) The connectivity of spinal circuits is much more divergent and convergent than expected. (b) The normal and reflex-induced recruitment of individual muscles and compartments of muscles is more finely controlled than was noted previously. (c) The mechanical interactions among linked skeletal segments and their often multiarticular muscles are neither simple nor intuitively obvious. We have developed a mathematical model of the cat hind limb that permits us to examine the influence of individual muscles on posture and gait. We have used linear quadratic control theory to predict the optimal distribution of feedback from a hypothetical set of proprioceptors, given different assumptions about the behavioral goals of the animal. The changes in these predictions that result from changes in the structure and control objectives of the model may provide insights into the functions actually performed by the various circuits in the spinal cord.

Morphological organization and contractile properties of the wrist flexor muscles in the cat.

A comparison of the anatomy, fiber type profiles, and contractile properties of the wrist flexor muscles was undertaken in the cat. Isometric contractile characteristics were measured for each muscle. Three muscle fiber types, FG, FOG, and SO, were differentiated by staining cross sections of each muscle for ATPase, NADH diaphorase, SDH, and alpha-GPD activities. The wrist flexor muscles ranged from less than 1% to 49% SO fiber content; with two of the five heads of the flexor digitorium profundus (FDP) having 1% or less SO fibers (FDP1-1.07%, FDP5-0.81%) and the humeral head of the flexor carpi ulnaris muscle (FCUh) having the greatest content of SO fibers. The mean contraction time (CT) plus one-half relaxation time for an isometric twitch was correlated with the percentage of SO fibers and ranged from 40.5 to 111.8 ms. Except for the FCU (37ms), the CT was less than 25 ms for the wrist flexor muscles. The uniarticular wrist flexor muscles, the flexor carpi radialis (FCR), and the FCU had the highest percentage of SO fibers and were more fatigue-resistant that the multiarticular muscles. Considerable differences exist in muscle structure, fiber type proportions, and contractile properties between the FCR and FCU, which may be related to functional differences between the two sides of the wrist that may exist during the placement of the foot during locomotion.