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PubMed2001

Arm to leg coordination in humans during walking, creeping and swimming activities.

In walking humans, arm to leg coordination is a well established phenomenon. The origin of this coordination, however, remains a matter for debate. It could derive from the intrinsic organisation of the human CNS, but it could also consist of a movement induced epiphenomenon. In order to establish which of these alternatives applies, we recorded arm and leg movements as well as their muscle activities during walking, creeping on all fours and swimming. The relationship between arm and leg cycle frequency observed under these various conditions was then investigated. We found that during walking, creeping on all fours or swimming, arm and leg movements remain frequency locked with a fixed relationship of 1/1, 2/1, 3/1, 4/1 or 5/1. When movements of the legs are slowed by flippers, the frequency relationship may skip to a different value, but the coordination is preserved. Furthermore, minimising the mechanical interactions between the limbs does not abolish coordination. These findings demonstrate that the arm to leg coordination observed in the walking human is also present during other human locomotor activities. The characteristics of this coordination correspond to those of a system of two coupled oscillators like that underlying quadruped locomotion.

Adult↗
PubMed2001

General coordination of shoulder, elbow and wrist dynamics during multijoint arm movements.

Studies of multijoint arm movements have demonstrated that the nervous system anticipates and plans for the mechanical effects that arise from motion of the linked limb segments. The general rules by which the nervous system selects appropriate muscle activities and torques to best deal with these intersegmental effects are largely unknown. In order to reveal possible rules, this study examined the relationship of muscle and interaction torques to joint acceleration at the shoulder, elbow and wrist during point-to-point arm movements to a range of targets in the horizontal plane. Results showed that, in general, dynamics differed between the joints. For most movements, shoulder muscle torque primarily determined net torque and joint acceleration, while interaction torque was minimal. In contrast, elbow and wrist net torque were determined by a combination of muscle and interaction torque that varied systematically with target direction and joint excursion. This "shoulder-centered pattern" occurred whether subjects reached targets using straight or curved finger paths. The prevalence of a shoulder-centered pattern extends findings from a range of arm movement studies including movement of healthy adults, neurological patients, and simulations with altered interaction effects. The shoulder-centered pattern occurred for most but not all movements. The majority of the remaining movements displayed an "elbow-centered pattern," in which muscle torque determined initial acceleration at the elbow and not at the shoulder. This occurred for movements when shoulder excursion was <50% of elbow excursion. Thus, both shoulder- and elbow-centered movements displayed a difference between joints but with reversed dynamics. Overall, these findings suggest that a difference in dynamics between joints is a general feature of horizontal plane arm movements, and this difference is most commonly reflected in a shoulder-centered pattern. This feature fits well with other general shoulder-elbow differences suggested in the literature on arm movements, namely that: (a) agonist muscle activity appears more closely related to certain joint kinematics at the shoulder than at the elbow, (b) adults with neurological damage display less disruption of shoulder motion than elbow motion, and (c) infants display adult-like motion first in the shoulder and last at the wrist.

Adult↗
PubMed2005

Comparisons of physiological and perceptual responses in healthy men and women during standardized arm cranking and task-specific pushing-pulling.

OBJECTIVE: Peak cardiorespiratory, metabolic, and perceptual responses in healthy men (n=11) and women (n=11) were compared during two different upper body exercise modes: standardized arm cranking and task-specific pushing-pulling. METHODS: Each subject completed to volitional exhaustion both an incremental arm cranking and a pushing-pulling exercise continuously, in a random order, on two separate days. Physiological responses were monitored using an automated metabolic cart and a heart rate monitor, and the rating of perceived exertion was obtained using a 15-point Borg Scale. RESULTS: Peak oxygen uptake, oxygen pulse, respiratory exchange ratio, and ventilation rate were higher and total exercise time to exhaustion was lower during arm cranking compared to pushing-pulling (P<0.05). However, heart rate was similar between exercise modes (P>0.05). Men showed greater physiological responses (absolute oxygen uptake, oxygen pulse, and ventilation rate) and longer exercise time to exhaustion than women (P<0.05). Power output during arm cranking was higher (by 79%) than pushing-pulling (P<0.01), with men demonstrating 30% greater values during both exercise modes (P<0.01). The lower power output generated during pushing-pulling resulted in a greater ratio of peak oxygen uptake to power output (by 72%; P<0.05). Interestingly, although power output and oxygen uptake were lower at the maximal workload, perceived exertion was higher (by 5%) during pushing-pulling (P<0.05). CONCLUSIONS: Based on the physiological differences, pushing-pulling is found to be metabolically less efficient than arm cranking. However, greater ratings of perceived exertion during pushing-pulling implies that the perception of effort can also be influenced by a low intensity task, such as pushing-pulling, if performed for a prolonged period. Occupational health professionals should be aware of the limitations of utilizing physiological and perceptual responses obtained only from standardized ergometric protocols in predicting the workers' performance effectiveness.

Adult↗
PubMed2004

Exercise capacity in young adults with hypertension and systolic blood pressure difference between right arm and leg after repair of coarctation of the aorta.

Coarctation of the aorta represents 5-7% of congenital heart defects. Symptoms and prognosis depend on the degree of stenosis, age at surgery, surgical method and the presence of other heart defects. Postoperative complications are hypertension, restenosis and an abnormal blood pressure response during exercise. This study includes 41 patients, 15-40 years old, operated in the period 1975-1996. All were exercised on a treadmill until maximal oxygen consumption was achieved. Blood pressure was measured in the right arm and leg before and immediately after exercise, and in the right arm during exercise. Oxygen consumption was monitored and we defined an aerobic phase, an isocapnic buffering phase and a hypocapnic hyperventilation phase. The resting systolic blood pressure correlates with the resting systolic blood pressure difference between right arm and leg. A resting systolic blood pressure difference between the right arm and leg of 0.13 kPa (1 mmHg) to 2.67 kPa (20 mmHg) corresponds with a slight increase in resting systolic blood pressure. This rise in blood pressure increases the aerobic phase of the exercise test, helping the patients to achieve higher maximal oxygen consumption. A resting systolic blood pressure difference of more than 2.67 kPa (20 mmHg) corresponds with severe hypertension and causes reduction in the aerobic phase and maximal oxygen consumption. Resting systolic blood pressure and resting systolic blood pressure difference between the right arm and leg are not indicators for blood pressure response during exercise. Exercise testing is important to reveal exercise-induced hypertension and to monitor changes in transition from aerobic to anaerobic exercise and limitation to exercise capacity.

Adolescent↗
PubMed2000

Validity of bioelectrical impedance and ultrasonographic methods for estimating the muscle volume of the upper arm.

The present study aimed to investigate the validity of bioelectrical impedance and ultrasonographic methods for predicting the muscle volume of the upper arm. Bioelectrical impedance of the right upper arm and the thickness of elbow flexor and extensor muscles were measured from 26 healthy young adult men using a specially designed bioelectrical impedance data acquisition system and brightness-mode ultrasound apparatus, respectively. As reference data, the muscle volume (MV(MRI)) of the right upper arm was determined using a magnetic resonance imaging method. The impedance index was calculated as L2/Z, where L is the upper arm length and Z is the impedance of the shoulder to the elbow. The muscle volume (MV(ULT)) was calculated as pi x (d/2)2 L, where d is muscle thickness. L2/Z and MV(ULT) were significantly correlated with MV(MRI) with correlation coefficients of 0.971 and 0.962, respectively. In these relationships, the standard errors of estimation were 44.2 cm3 (6.3%) for L2/Z and 50.7 cm3 (7.2%) for MV(ULT). There was no significant difference between the absolute errors of muscle volumes estimated by L2/Z and MV(ULT): 36.2 (4.8, SEM) cm3 for L2/Z versus 40.3 (5.8) cm3 for MV(ULT). The present results suggest that both bioelectrical impedance and ultrasonographic methods may be useful for predicting the muscle volume of the upper arm.

Adult↗
PubMed2000

Intramuscular pressure of the infra- and supraspinatus muscles in relation to hand load and arm posture.

In work engaging the upper extremities, the musculoskeletal system of the shoulder is sometimes exposed to prolonged excessive load, leading to musculoskeletal disorders of the shoulder. One way of reducing work-related shoulder disorders is to establish guidelines for working postures. The purpose of this study was to identify harmful working positions, by performing a comprehensive survey of the intramuscular pressure (IMP) in the infra- and supraspinatus muscles in relation to different arm positions and external loads. Ten healthy males participated, and the IMP in the infra- and supraspinatus muscles was studied in a total of 112 combinations of arm positions and hand loads at levels that occur frequently in industrial work. High-precision spatial recordings were accomplished with a three-dimensional motion-analysis system, and the IMP was measured using the microcapillary infusion technique. The mean IMP of the infraspinatus muscle as well as that of the supraspinatus muscle increased continuously from a resting pressure at 0 degrees of upper arm elevation to a maximal pressure at 90 degrees of upper arm elevation, for all elevation planes. The mean IMP of the supraspinatus muscle appeared to be more dependent upon the elevation plane and less dependent upon the hand load, compared to the infraspinatus muscle. Even during only moderate arm elevation, the mean IMP of the infra- and supraspinatus muscles, presented here in polar diagrams, had already exceeded the levels of reduced recovery from local muscle fatigue and blood flow impairment. The elevation angle and the hand load primarily influence the development of IMP in the infra- and supraspinatus muscles.

Adult↗
PubMed1997

Analysis of an optimal control model of multi-joint arm movements.

In this paper, we propose a model of biological motor control for generation of goal-directed multi-joint arm movements, and study the formation of muscle control inputs and invariant kinematic features of movements. The model has a hierarchical structure that can determine the control inputs for a set of redundant muscles without any inverse computation. Calculation of motor commands is divided into two stages, each of which performs a transformation of motor commands from one coordinate system to another. At the first level, a central controller in the brain accepts instructions from higher centers, which represent the motor goal in the Cartesian space. The controller computes joint equilibrium trajectories and excitation signals according to a minimum effort criterion. At the second level, a neural network in the spinal cord translates the excitation signals and equilibrium trajectories into control commands to three pairs of antagonist muscles which are redundant for a two-joint arm. No inverse computation is required in the determination of individual muscle commands. The minimum effort controller can produce arm movements whose dynamic and kinematic features are similar to those of voluntary arm movements. For fast movements, the hand approaches a target position along a near-straight path with a smooth bell-shaped velocity. The equilibrium trajectories in X and Y show an "N' shape, but the end-point equilibrium path zigzags around the hand path. Joint movements are not always smooth. Joint reversal is found in movements in some directions. The excitation signals have a triphasic (or biphasic) pulse pattern, which leads to stereotyped triphasic (or biphasic) bursts in muscle control inputs, and a dynamically modulated joint stiffness. There is a fixed sequence of muscle activation from proximal muscles to distal muscles. The order is preserved in all movements. For slow movements, it is shown that a constant joint stiffness is necessary to produce a smooth movement with a bell-shaped velocity. Scaled movements can be reproduced by varying the constraints on the maximal level of excitation signals according to the speed of movement. When the inertial parameters of the arm are altered, movement trajectories can be kept invariant by adjusting the pulse height values, showing the ability to adapt to load changes. These results agree with a wide range of experimental observations on human voluntary movements.

Arm↗
PubMed1999

Three-dimensional kinematic analysis of influence of hand orientation and joint limits on the control of arm postures and movements.

The problems related to kinematic redundancy in both task and joint space were investigated for arm prehension movements in this paper. After a detailed analysis of kinematic redundancy of the arm, it is shown that the redundancy problem is ill posed only for the control of hand orientation. An experiment was then designed to investigate the influence of hand orientation on the control of arm movements. Since movements must be made within the limits of the joints, the influence of these limits was also analyzed quantitatively. The results of the experiment confirm that the increase of movement time because of the change of object orientation is due to the lengthening of the deceleration phase disproportionately to the rest of the movement. The variation of hand path due to the change of object orientation was observed as being surprisingly small for some subjects as opposed to the large range of object orientation, implying that hand path and hand orientation could be controlled separately, thus simplifying the computational problem of inverse kinematics. Moreover, the observations from the present experiment strongly suggest that a functional segmentation of the proximal and distal joints exists and that the control of wrist motion is dissociated from the rest of joint motions. The contribution of each joint in the control of arm movements could be determined through the principle of minimum energy and minimum discomfort under the constraints of the joint limits. A simplified inverse kinematics model was tested. It shows that these hypotheses can be easily implemented in a geometric algorithm and be used to predict arm prehension postures reasonably well under the constraints of joint limits.

Adult↗
PubMed2002

Restoration of upper arm function in traction injuries to the brachial plexus.

BACKGROUND: Restoration of upper arm function presents the main priority in nerve repair of brachial plexus traction injuries. The results are predominantly influenced by the level and extent of injury, and the type of surgical procedure. The purpose of this study is to evaluate influence of these factors on final outcome. METHODS: Study included 91 surgically treated patients, including 71 patients with avulsions of one or more spinal nerve roots and 20 with peripheral traction injuries. We performed 120 nerve transfers, 25 nerve graftings and 29 neurolyses on different nerve elements depending on the type of nerve damage. Analysis of motor recovery for elbow flexion and arm abduction, isolated or in combination, was done. FINDINGS: Recovery of elbow flexion was obtained in 75% nerve transfers, and in 68,7% nerve graftings in peripheral traction injuries. Recovery of arm abduction was obtained in 78,5% nerve transfers, and in 44,4% nerve graftings in peripheral traction injuries. Neurolysis was successful in all cases. Generally, the quality of recovery was better for the musculocutaneous nerve. Useful global upper arm function was obtained in 49,3% of patients with avulsion of spinal nerve roots, and in 55% of patients with peripheral traction injuries. INTERPRETATION: Regarding upper arm function the prognosis of surgically treated patients with traction injuries to the brachial plexus is generally similar in cases with central or peripheral level of injury. However, nerve transfers of collateral branches seem to be superior to nerve grafting and may be another possibility for repair in cases with extensive nerve gaps.

Adolescent↗
PubMed2000

A case of spontaneous arm levitation in progressive supranuclear palsy.

Progressive supranuclear palsy is one of the parkinsonial syndromes causing atypical parkinsonism. In recent reports, other than subcortical involvement, also cortical structures have been shown to be involved in progressive supranuclear palsy patients. One of the clinical presentations of this involvement is spontaneous arm levitation which is a component of alien limb syndrome. Here we report a clinically diagnosed progressive supranuclear palsy patient with spontaneous arm levitation. Clinically spontaneous levitation of one arm without denial of ownership suggests the presence of spontaneous arm levitation. Spontaneous arm levitation can occur in the setting of progressive supranuclear palsy and it possibly demonstrates the cortical involvement in this disorder.

Aged↗
PubMed1992

Exercise testing and training of persons with dysvascular amputation: safety and efficacy of arm ergometry.

Recent studies indicate that most persons with dysvascular amputation also have moderate to severe cardiovascular disease with impairment in functional capacity. This may limit the ability to achieve optimal function with their prosthesis because of inadequate conditioning. We developed an exercise testing and training program using arm ergometry in conjunction with standard rehabilitation for persons with acute dysvascular amputation who were profoundly deconditioned after complicated perioperative courses. The program consisted of daily arm ergometry, performed on an interval basis, at an intensity individually optimized through exercise testing. Twenty-five patients, with a mean age of 63 years, completed the inpatient program with pretest and discharge work performance assessment. There was no significant difference between pretest and discharge assessment of baseline or peak heart rate, systolic blood pressure, diastolic blood pressure, or Borg rating of perceived exertion. Peak systolic blood pressure was elevated at discharge compared to admission testing (p less than .04). Heart rate responses were decreased during the early stages of testing when comparing discharge telemetry to admission findings. The duration of exercise increased from 12.6 minutes to 16.3 minutes (p less than .0004), and the maximum work output increased from 17.1 watts to 23.5 watts (p less than .0004). There was no significant morbidity associated with either arm ergometry testing or the exercise program. We conclude that arm ergometry testing and training is a safe and effective method for improving the efficiency of arm work in the patient with acute dysvascular amputation.

Aged↗
PubMed1988

Unit activity in the cerebellar nuclei related to arm reaching movements.

Single units in the fastigial, interpositus and dentate nuclei of two stump-tail macaque monkeys were studied in relation to a right arm, visually guided reaching task. Of 638 recorded cells, 149 showed activity changes correlated to the task, including 24 in the contralateral fastigial and interpositus. Reach-related discharge patterns fell into two broad categories, tonic and phasic. Tonic responses were maintained throughout the reach with no observable relation to kinematic parameters. Most of the task-related activity occurred during the upward lift of the arm toward the target button, with a drop-off as the arm was lowered toward the rest plate. Phasic response cells fired bursts (or suppressed discharge) at specific points in the arm trajectory, most commonly during the lift phase. Many had a sharp drop in discharge when the shoulder flexion torque was transiently reversed to decelerate the arm. For either type, restricted directional specificity was rarely seen in any nucleus, and correlations with recorded EMGs were weak. Visual responses to target button illumination were observed in both the fastigial and dentate nuclei, but did not necessarily correspond with the button giving the best movement-related response. Task-related activity changes started earliest in the fastigial nuclei and latest in the interpositus nuclei. The data suggested that cerebellar output facilitates motor centers in a rather general manner, but at precisely determined times.

Animals↗
PubMed1996

Soleus H-reflex depression induced by ballistic voluntary arm movement in human.

A biomechanical and neurophysiological analysis of anticipatory postural adjustments associated with the early phase of a voluntary arm movement was carried out in normal human subjects. Arm elevation, performed at maximal velocity, was studied with unilateral arm movement in freely and counterbalanced (suspended in a safety harness) standing humans. The ground reaction force of both legs, tangential acceleration of the shank and electromyographic activity (EMG) of the anterior deltoid (AD), biceps femoris (BF) and soleus (Sol) muscles were recorded. Sol H-reflexes of both legs were also elicited. To examine how the Ia inhibitory and presynaptic inhibitory pathways are related to anticipatory postural adjustments, additional Sol H-reflexes were elicited using the classical conditioning-test technique (time interval 2 and 15 ms, respectively). In this study, we systematically described biomechanical and EMG phenomena that precede and follow the onset of voluntary arm movements. Prior to and during the arm movement (i.e. AD activation), a sequence of EMG modifications occurred in ipsilateral BF and Sol muscles. Those modifications preceding BF activation included silent phases in Sol EMG and depression of Sol H-reflexes. By comparing EMG modifications with depressions of the Sol H-reflex, we conclude that Ia and presynaptic inhibitory pathways do not play a specific role in those Sol H-reflex depressions. Moreover, because Sol H-reflex depression occurs in both freely standing and counterbalanced postures, anticipatory postural adjustment appear to be preprogrammed in the central nervous systems unrelated to peripheral neural mechanisms. Since changes of EMG activities of ipsilateral BF and Sol appeared simultaneously and Sol H-reflex depressions were dependent on EMG activities of ipsilateral BF, control commands to anticipatory postural adjustment would excite BF and inhibit Sol.

Adult↗
PubMed1991

An improved biomechanical model for simulating the strain of the hand-arm system under vibration stress.

In order to define relationships between the vibration stress and the strain of the human hand-arm system a biomechanical model was developed. The four masses of the model representing the hand, the forearm and the upper arm were connected by dampers and springs in two perpendicular directions. Simulating muscle activity, damped torsion springs were included additionally. The motions of the model were described by a differential matrix equation which was solved by using a 'transfer matrix routine' as well as by numerical integration. Thus, functions with harmonic or transient time courses could be selected as an excitation. The simulated vibrations were compared with those of other hand-arm models. The forces and torques transmitted between the masses, and the energy dissipated by the dampers were computed for several combinations of exciter frequencies and accelerations. The dependence of torques upon excitation agreed fairly well with the behaviour of the arm muscles under vibration as described by various investigators. At frequencies above 100 Hz the energy was dissipated mainly by the dampers between the masses near to the exciter. Transferring this result to the hand-arm system it shows that at high frequencies energy is dissipated by the hand and its palmar tissues and this might be one cause for the incidence of vibration-induced white finger disease.

Arm↗
PubMed1994

Hypothetical joint-related coordinate systems in which populations of motor cortical neurons code direction of voluntary arm movements.

Results of the recent electrophysiological experiments by Caminiti et al. suggest that populations of neurons of the motor areas code direction of voluntary arm movement in an intrinsic coordinate system. In this letter I propose a set of joint-related coordinate systems that rotate with the posture of the arm in which populations of motor cortical neurons code direction of the arm movement. In these frames of reference, the movement directions represented vary with the posture of the arm but the preferred directions of the motor cortical neurons do not rotate. It is suggested that the difference in the neuronal activity for different workspaces, which was observed by Caminiti et al., is due to the dependence of the movement direction, represented in one of the joint-related coordinate systems, on the posture of the arm.

Arm↗
PubMed1992

How musculotendon architecture and joint geometry affect the capacity of muscles to move and exert force on objects: a review with application to arm and forearm tendon transfer design.

This commentary reviews musculotendon architecture and the relation between architectural parameters and the force, speed, and excursion capacity of musculotendon units. It is hoped that this review will help provide the framework within which to appreciate the importance of the data presented by Lieber et al. Muscle fiber pennation hardly affects musculotendon output of forearm and hand muscles. Instead, physiologic cross-sectional area and muscle fiber length affect force capacity and speed and excursion capacity, respectively. How muscles with equal mass can have different force, speed, and excursion capacities is explained. Since the moment arm of a muscle (the shortest distance from the musculotendon unit to the joint center of rotation) transforms muscle output into musculotendon output, it is shown why the capacity for a muscle to exert force on an object, as during grasping, is directly proportional to its moment arm and why the range of joint movement and speed over which muscles exert force is inversely proportional to the moment arm. Finally, tendon, being not stiff in forearm and hand musculotendon units, also affects their output. Criteria are given for designing tendon transfer reconstructions from architectural data and moment arm data to best replicate the biomechanical function of the replaced muscle. To have the same capacity for imparting movement to objects and exerting force on them, the donor muscle should have the same moment arm/physiologic cross-sectional area product, the same fiber length/moment arm ratio, and the same tendon length/muscle fiber length ratio as the replaced muscle.

Arm↗
PubMed2004

Development of exercise-induced arm-leg blood pressure gradient and abnormal arterial compliance in patients with repaired coarctation of the aorta.

Often, the lack of systemic arterial hypertension and the lack of a resting arm-leg blood pressure gradient are used to assess the adequacy of the anatomic result after intervention for coarctation of the aorta (CoA). Some patients with no arm-leg gradient at rest may develop a gradient with exercise, leading caregivers to question the success of the repair. It is not clear what the prevalence is of patients who have undergone a successful intervention for CoA and have no arm-leg gradient at rest but develop a significant gradient with exercise and which factors may predict the development of an arm-leg gradient with exercise. This study evaluates the prevalence and predictors of an exercise-induced arm-leg gradient in subjects who have undergone an apparently successful intervention for CoA.

Adolescent↗
PubMed2005

Influence of breech presentation on the development of fetal arm posture.

BACKGROUND: In previous research, an age-related developmental trend towards increasing arm flexion has been found for cephalic fetuses. AIM: To determine if the development of arm posture in breech fetuses is comparable to that of cephalic ones. SUBJECTS AND METHODS: Fetal arm posture was studied longitudinally by means of real-time ultrasound in 13 healthy breech and 10 healthy cephalic fetuses. Observations started from 33 weeks gestational age until birth and were performed weekly in the breech group and every 2 weeks in the cephalic group. RESULTS: No difference could be found in arm posture between the left and the right arm in either group. Both breech and cephalic fetuses showed a clear preference for flexion in elbow and finger joints at all studied ages. After 36 weeks gestational age, the breech group showed significantly less wrist flexion when compared to the cephalic group (p = 0.037). A clear preference for location of the fetal hands near the fetal head could be observed for both groups. CONCLUSIONS: As there is no evidence for an abnormal neuromotor development in healthy breech fetuses, the observed difference in wrist flexion is probably due to differences in intrauterine environment. Because of the preference for location of the hands in the vicinity of the fetal head, breech fetuses probably experience a less restricted environment (in the upper part of the uterus) than cephalic fetuses (in the lower part of the uterus).

Arm↗