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PubMed2005

Muscle arm development in Caenorhabditis elegans.

In several types of animals, muscle cells use membrane extensions to contact motor axons during development. To better understand the process of membrane extension in muscle cells, we investigated the development of Caenorhabditis elegans muscle arms, which extend to motor axons and form the postsynaptic element of the neuromuscular junction. We found that muscle arm development is a highly regulated process: the number of muscle arms extended by each muscle, the shape of the muscle arms and the path taken by the muscle arms to reach the motor axons are largely stereotypical. We also investigated the role of several cytoskeletal components and regulators during arm development, and found that tropomyosin (LEV-11), the actin depolymerizing activity of ADF/cofilin (UNC-60B) and, surprisingly, myosin heavy chain B (UNC-54) are each required for muscle arm extension. This is the first evidence that UNC-54, which is found in thick filaments of sarcomeres, can also play a role in membrane extension. The muscle arm phenotypes produced when these genes are mutated support a 'two-phase' model that distinguishes passive muscle arm development in embryogenesis from active muscle arm extension during larval development.

Actin Depolymerizing Factors↗
PubMed1996

XiTec XiScan 1000 mini C-arm unit.

Mini C-arm units are small, mobile fluoroscopic imaging systems-essentially miniaturized versions of mobile C-arm units. They are used most often by hand and foot surgeons to image the extremities (e.g., fingers, hand, foot). In this Evaluation, we tested the XiScan 1000 mini C-arm unit, equipped with a 6.7 cm (2.6 in) diameter image intensifier, manufactured by XiTec, Inc. (We also partially tested and rated a version of this unit with a 10 cm [4 in] image intensifier.) This study is an update of our previous mini C-arm unit Evaluation covering the FluoroScan, published in Health Devices 24(2), February 1995. Except where noted, we tested the new unit against the same criteria and using the same test methods as described in the original study. For the sake of brevity, we have not repeated our criteria or test methods in this issue. Readers wishing that information should refer to the original Evaluation or contact ECRI. In addition, the original Evaluation includes a Clinical and Technical Overview detailing many of the technical features and issues touched on below. We also draw readers' attention to other material we have published on C-arms: our Evaluation of mobile C-arms in August 1990 (19[8]), our Single Product Evaluation of the IMS Exposcop Plus mobile C-arm in March 1993 (22[3]), and our Update of the FluoroScan Evaluation in December 1995 (24[12]). Readers are cautioned not to base purchasing and use decisions on our rating alone, but on a thorough understanding of our conclusions and the issues surrounding mini C-arm units, which can be gained by reading this study and the February 1995 Evaluation in their entirety. For additional perspectives on fluoroscopy and the operation of C-arm units, refer to our earlier Evaluations of conventional C-arm units.

Evaluation Studies as Topic↗
PubMed2000

Arm restlessness in patients with restless legs syndrome.

Restless legs syndrome (RLS) is a neurologic disorder characterized principally by leg paresthesia and motor restlessness. Several clinical reports indicated that many patients with RLS also have arm paresthesia and restlessness. In the present study, the incidence of arm restlessness was assessed by questionnaire in 230 patients diagnosed with idiopathic RLS. Arm restlessness was reported by 48.7% of the patients. Patients with and without arm restlessness were compared with regard to clinical and polysomnographic parameters. No between-group differences were found for age at onset of RLS, duration of illness, gender, presence of a family history of RLS, sleep latency, total sleep time, sleep efficiency, and periodic leg movements index during sleep. However, arm restlessness was more frequent in patients with severe RLS. Interestingly, the polysomnographic data failed to differentiate the patients with arm restlessness from those without arm restlessness, except for sleep efficiency, which tended to be lower in patients with arm restlessness. In conclusion, the results of the present study are in agreement with clinical observations that a large proportion of patients with RLS have arm restlessness.

Adult↗
PubMed2002

Patterns of connections between the musculocutaneous and median nerves in the axilla and arm.

Variations in connections between the musculocutaneous and median nerves in the arm are not as uncommon as was once thought. This opinion led us to perform a study in 138 cadavers (66 male, 72 female). These variations were seen in 64 cadavers (46.4%), 9 bilaterally and 55 unilaterally (26 right and 29 left); in total, therefore, variations were observed in 73 out of 276 arms (26.4%), 42 male and 31 female. No statistically significant differences by gender and side were observed. We classify the variations in three main patterns: Pattern 1, fusion of both nerves (14 arms, 19.2%); Pattern 2, presence of one supplementary branch between both nerves (53 arms, 72.6%); and Pattern 3, two branches (5 arms, 6.8%). Pattern 2 was further subdivided into a sub-group 2a when a single root from the musculocutaneous nerve contributed to the connection (51 arms, 69.9%), and 2b when there were two roots from the musculocutaneous nerve (2 arms, 2.7%). A combination of Patterns 1 and 2a was observed in one case (1.4%). Further variations are described, published classification systems are reviewed and a meta-analysis of previous results is presented. An overall incidence of 33% of variant arms was observed. Of these variant arms, Pattern 1 represented 13.1%, Pattern 2 represented 75.4%, and Pattern 3, 8.5%, similar to our figures.

Aged↗
PubMed1990

Electromyographic activity in the shoulder-neck region according to arm position and glenohumeral torque.

The electromyographical (EMG) response to isometric ramp contractions of the right arm, the left arm, and both arms was studied using four pairs of surface electrodes above the right upper trapezius muscle (UT) of six men and six women. Contractions were made against gravity with the active arm(s) in eight positions, ranging from flexion to abduction. To describe arm positions, new, simple terminology was developed. Root mean square (rms)-converted EMG-signals were normalized (EMGnorm) with respect to a reference contraction. The EMGnorm corresponding to a 15 N.m torque in the right glenohumeral (GH) joint was strongly related to the position of the right arm (P less than 0.001). The shape of this relationship depended on the electrode position (P less than 0.001). The ratio between EMGnorm at 30 N.m and 15 N.m GH torques was related to arm position (P less than 0.001) and differed between electrodes (P less than 0.001). A left-side GH torque resulted in right-side (contralateral) EMG activity, typically corresponding to 20%-30% of that obtained during similar right-side GH torque. Bilateral GH torque implied 0%-50% increase in EMG activity as compared to that obtained with the right arm alone. The results have shown that signals from one pair of surface electrodes above UT cannot be taken as representative of the EMG activity from electrodes located elsewhere above UT. The EMG recordings reflected a complex pattern of muscular activation, significantly related to both outwardly visible factors (arm position, GH torque), and within-body servosystems (motor control reflexes).

Adult↗
PubMed1994

Cardiovascular responses of cardiac transplant patients to arm and leg exercise.

This investigation compares the cardiovascular responses of normal (n = 10) and cardiac transplant (n = 14) subjects to peak arm and leg exercise. It also tests the hypothesis that the higher heart rate (fc) in normal subjects during light (30 W) submaximal arm versus leg exercise is due to cardiac innervation. In cardiac transplant patients, power output, oxygen consumption (VO2), fc and rate pressure product were 54%, 28%, 7%, and 8% lower during peak arm than leg exercise, respectively. In normal subjects, power output, VO2, fc and rate pressure product were 61%, 33%, 8%, and 11% lower during peak arm than leg exercise, respectively. In cardiac transplant patients there was no significant difference in absolute fc during submaximal arm and leg exercise. In normal subjects, absolute fc during arm and leg exercise was [mean (SD)] 97 (4) beats.min-1 and 92 (4) beats.min-1, respectively (P = 0.07). Plasma noradrenaline was increased more during arm than leg exercise in both cardiac transplant and normal subjects. Maximal leg testing is useful when determining the capacity of cardiac transplant patients to perform arm work. The higher absolute fc reported by other investigators for normal subjects during submaximal arm versus leg exercise may be mediated by cardiac innervation.

Arm↗
PubMed2002

Hand-eye coordination for rapid pointing movements. Arm movement direction and distance are specified prior to saccade onset.

Visually guided arm movements such as reaching or pointing are accompanied by saccadic eye movements that typically begin prior to motion of the arm. In the past, some degree of coupling between the oculomotor and limb motor systems has been demonstrated by assessing the relative onset times of eye and arm movement, and by the demonstration of a gap effect for arm movement reaction times. However, measures of limb movement onset time based on kinematics are affected by factors such as the relatively high inertia of the limb and neuromechanical delays. The goal of the present study was thus to assess the relative timing of rapid eye and arm movements made to visual targets by examining electromyographic (EMG) activity of limb muscles in conjunction with eye and arm position measures. The observation of a positive correlation between eye and limb EMG onset latencies, and the presence of a gap effect for limb EMG onset times (a reduction in reaction time when a temporal gap is introduced between the disappearance of a central fixation point and the appearance of a new target) both support the idea that eye and arm movement initiation are linked. However, limb EMG onset in most cases precedes saccade onset, and the magnitude of EMG activity prior to eye movement is correlated with both the direction and amplitude of the upcoming arm movement. This suggests that, for the rapid movements studied here, arm movement direction and distance are specified prior to the onset of saccades.

Arm↗
PubMed2005

Control of double-joint arm posture in adults with unilateral brain damage.

It has been suggested that multijoint movements result from the specification of a referent configuration of the body. The activity of muscles and forces required for movements emerge depending on the difference between the actual and referent body configurations. We identified the referent arm configurations specified by the nervous system to bring the arm to the target position both in healthy individuals and in those with arm motor paresis due to stroke. From an initial position of the right arm, subjects matched a force equivalent to 30% of their maximal voluntary force in that position. The external force, produced at the handle of a double-joint manipulandum by two torque motors, pulled the hand to the left (165 degrees ) or pushed it to the right (0 degrees ). For both the initial conditions, three directions of the final force (0 degrees , +20 degrees , and -20 degrees ) with respect to the direction of the initial force were used. Subjects were instructed not to intervene when the load was unexpectedly partially or completely removed. Both groups of subjects produced similar responses to unloading of the double-joint arm system. Partial removal of the load resulted in distinct final hand positions associated with unique shoulder-elbow configurations and joint torques. The net static torque at each joint before and after unloading was represented as a function of the two joint angles describing a planar surface or invariant characteristic in 3D torque/angle coordinates. For each initial condition, the referent arm configuration was identified as the combination of elbow and shoulder angles at which the net torques at the two joints were zero. These configurations were different for different initial conditions. The identification of the referent configuration was possible for all healthy participants and for most individuals with hemiparesis suggesting that they preserved the ability to adapt their central commands-the referent arm configurations-to accommodate changes in external load conditions. Despite the preservation of the basic response patterns, individuals with stroke damage had a more restricted range of hand trajectories following unloading, an increased instability around the final endpoint position, altered patterns of elbow and shoulder muscle coactivation, and differences in the dispersion of referent configurations in elbow-shoulder joint space compared to healthy individuals. Moreover, 4 out of 12 individuals with hemiparesis were unable to specify referent configurations of the arm in a consistent way. It is suggested that problems in the specification of the referent configuration may be responsible for the inability of some individuals with stroke to produce coordinated multijoint movements. The present work adds three findings to the motor control literature concerning stroke: non-significant torque/angle relationships in some subjects, narrower range of referent arm configurations, and instability about the final position. This is the first demonstration of the feasibility of the concept of the referent configuration for the double-joint muscle-reflex system and the ability of some individuals with stroke to produce task-specific adjustments of this configuration.

Adaptation, Physiological↗
PubMed2005

Temporal coordination of the arms during bilateral simultaneous and sequential movements in patients with chronic hemiparesis.

Upper extremity (UE) hemiparesis results in decreased movement speed and impaired coordination leading to functional limitations and disability. The effects of UE hemiparesis on bilateral functional reaching have not been studied even though most activities of daily living are bilateral tasks. We examined the characteristics of bilateral simultaneous (SIM-B) and bilateral sequential paretic-lead (SEQ-P) and nonparetic-lead (SEQ-NP) functional reaching tasks at preferred and fast speeds. Sixteen patients with chronic hemiparesis completed three bilateral reaching tasks as fast as possible. A subset of eight participants attempted to complete the tasks at both preferred and fastest possible speeds. Paretic (P) and nonparetic (NP) arms were not different from each other in movement time (MT) or peak velocity in the SIM-B condition. MT and peak velocity differed between the two arms during both SEQ tasks. P MT was shorter and NP MT longer in the SIM-B task compared to SEQ-P and SEQ-NP. The P arm MT was the shortest when moving with the NP arm in a simultaneous task compared to both P and NP lead sequential movements. Despite hemiparesis, the two arms demonstrate a temporal coupling when moving simultaneously. When attempting to move at fastest speed, P arm MT time is better when reaching before or with the NP arm than when reaching after the NP arm showing coupling to the NP limb and increased speed of movement. These coupling effects support the rationale for bilateral arm training for individuals with UE hemiparesis.

Aged↗
PubMed1998

Long-term loading and regional bone mass of the arm in female volleyball players.

In the present study, we compared the bone mineral content (BMC) and bone mineral density (BMD) in the arms of 11 female volleyball players (mean age 22.0 +/- 2.6 years) training for about 8 hours/week, and 11 nonactive females aged 24.6 +/- 3.1 years (mean +/- SD) not participating in regular or organized sport activity. Using dual X-ray absorptiometry (DXA), BMC was measured in the proximal and distal humerus, and BMD in the distal radius. Isokinetic concentric peak torque (highest value attained during 5 or 10 repetitions) of the rotator muscles of the shoulder and flexor and extensor muscles of the elbow were measured using an isokinetic dynamometer. The volleyball players had significantly higher BMC (P < 0.05) at the proximal humerus of the dominant arm compared with the nonactive group, but there were no differences between the groups in BMC of the distal humerus and BMD of the distal radius. In the volleyball players, BMC was significantly higher at the proximal humerus, at the distal humerus, and at the distal radius in the dominant compared with the nondominant arm. In the nonactive group, there were no significant differences in BMC and BMD between the dominant and nondominant arm at any site measured. Except for shoulder internal rotation strength and elbow flexion strength at 90 degrees/second that was higher in the dominant arm in the volleyball players, there were no significant differences in muscle strength of the rotator muscles of the shoulder and flexor and extensor muscles of the elbow between the dominant and nondominant arm in the volleyball players and nonactive controls. In the volleyball players, but not in the nonactive controls, there were several significant relationships between shoulder and elbow strength and BMC at the distal humerus of the dominant and especially the nondominant arm. These results show that young female volleyball players have a higher bone mass in the proximal humerus, distal humerus, and distal radius in the dominant compared with the nondominant arm, and a higher bone mass in the proximal humerus compared with nonactive controls. Muscle strength of the rotator muscles of the shoulder is not related to the higher bone mass in the proximal humerus of the dominant arm. Theoretically, the observed differences in bone mass can be related to the type of loading the skeleton undergoes when playing volleyball.

Adipose Tissue↗
PubMed2006

Early self-reported impairments in arm functioning of primary breast cancer patients predict late side effects of axillary lymph node dissection: results from a population-based cohort study.

OBJECTIVES: Improvements in the life expectancy of women with breast cancer raise important questions how to improve quality of life (QoL) for women sustaining complications and side effects of cancer treatment. The presented study examined the prevalence of arm morbidity in a cohort of primary breast cancer patients over time as a result of the extent of axillary lymph node dissection. Of particular interest is the question of using a recognized QoL assessment instrument at defined assessment points as an endpoint criteria of oncological treatment. METHODS: A prospective, population-based, longitudinal cohort study of patients with primary breast cancer was performed (n = 389). QoL data (EORTC QLQ C30 + BR23) and clinical data were assessed at designated time points. Primary endpoint of this analysis was patient reported arm morbidity assessed with the three-idem scale in the BR 23 (swelling, moving, pain). RESULTS: 20% of the patients evidenced considerable impairments in arm functioning. Arm morbidity was significantly related to the number of lymph nodes dissected (P < 0.002 entire cohort, P < 0.001 lymph node negatives) and was independent of age, stage of the disease, kind of breast surgery and radiation treatment. Early impairments in arm functioning (below 50 score values) assessed within 6 months after axillary surgery was a good predictor for late arm morbidity at 12 months RR 11.5 (CI 95% 4.7-28.4), 24 months RR 6.0 (CI95% 2.8-13.3) and 36 months RR 3.8 (CI 95% 1.8-7.9). CONCLUSIONS: Arm morbidity after axillary surgery is a severe and chronic condition affecting many breast cancer patients. The recognized QoL assessment instrument depict patients with severe impairments in arm functioning after axillary lymph node dissection and predict late arm morbidity. To increase patients' quality of life it thus may serve as a valid assessment tool for screening, allowing early referral for treatment and monitoring.

Aged↗
PubMed1986

Comparison of determinants of myocardial oxygen consumption during arm and leg exercise in normal persons.

Arm exercise assumes an increasingly important role in clinical cardiology as it is used in both exercise testing and training of patients with coronary artery disease. The effects of arm exercise on myocardial oxygen consumption are not well understood; they may differ from the effects of leg exercise. Previous studies have shown that the ischemic threshold is higher in patients performing arm exercise and leg exercise at the same heart rate-blood pressure product. The contribution of other determinants of myocardial oxygen consumption--left ventricular (LV) peak meridional systolic wall stress and contractility--to these observed differences were studied. Thirty healthy subjects exercised to the same peak rate-pressure product during dynamic upper- and lower-extremity exercise. Peak workload was lower during arm exercise (100 +/- 16 W) than during leg exercise (170 +/- 21 W, p less than 0.001). LV wall stress did not differ during either form of exercise (197 +/- 44 vs 204 +/- 33 dynes/cm2 X 10(3), arm vs leg, respectively). This was also true of contractility as assessed by the velocity of circumferential fiber shortening (2.8 +/- 0.6 vs 2.5 +/- 0.4 circ/s, arm vs leg, respectively) and the preejection period/LV ejection time ratio (0.33 +/- 0.11 vs 0.31 +/- 0.07, arm vs leg, respectively). Normal subjects exercising to a similar rate-pressure product showed the same levels of LV wall stress and contractility for arm and leg exercise despite the lower workload performed with arm exercise.

Adult↗
PubMed1990

Patency of arm vein grafts used in aorto-coronary bypass surgery.

Arm veins have been used in myocardial revascularisation procedures as a last resort bypass conduit because of their associated low patency. Nevertheless, leg veins and mammary arteries, which are the most commonly used, are sometimes not sufficient, leaving little choice as to the bypass conduit. To assess the properties of arm veins in bypass surgery, we compared a group of 28 patients that underwent an arm vein graft coronary bypass procedure with a matched group of patients in which leg veins were used. In 28 patients, 40 arm vein grafts with 77 distal anastomoses were used (mean 1.9 +/- 0.9; range 1-5). A cerebrovascular accident was the cause of the sole death (2%) during the study period. The mean follow-up was 4.6 years (Standard deviation, SD: 1.5 years). More antianginal medication was used in the arm vein group (P = 0.017). Additionally, the percentage of the expected maximal frequency during exercise testing was lower in the arm vein group as compared to the leg vein group. Digital subtraction angiography showed that the patency of the arm vein bypass grafts was 47% (70% confidence limits, CL: 32%-62%) while the patency of the leg vein grafts was 77% (CL: 64%-87%), which was statistically significant (P = 0.051). Comparison of these figures with the few published reports on arm veins used as coronary bypass grafts reveals similar results. We conclude that the arm vein as a coronary bypass graft is only to be used when mammary arteries and leg veins are not available.

Arm↗
PubMed2005

Arthroscopically repaired Bankart lesions and the effect of two different arm positions on immediate postoperative evaluation with magnetic resonance arthrography.

PURPOSE: To evaluate and describe the findings of immediate postoperative magnetic resonance (MR) arthrography of repaired capsulolabral buttress using 2 different arm positions (internal rotation and external rotation) for patients who have undergone arthroscopic Bankart repair. TYPE OF STUDY: Case series. METHODS: Arthroscopically repaired Bankart lesions in 22 nonconsecutive patients were examined with axial T2-weighted MR arthrography. We studied each of the 22 shoulders on the day of surgery for each patient. We measured 3 parameters (height, slope, and medial overhang) on the axial image at the anteroinferior portion of the glenoid (near the most inferior anchor) while placing each patient's arm into 2 different positions. The first involved internal rotation and the second, external rotation of the shoulder with the arm held at the side of the trunk and the elbow at 90 degrees flexion. The mean internal rotation of the arm was 30 degrees (range, 14 degrees to 45 degrees) and the mean external rotation was 19 degrees (range, 2 degrees to 44 degrees). RESULTS: The mean labral height and slope differences between the 2 arm positions were 1.47 mm (standard deviation [SD], 0.75 mm; range, 0.6 mm to 3.5 mm; P < .001) and 6.91 degrees (SD, 3.4 degrees; range, 2.2 degrees to 11.2 degrees; P < .001), respectively. Medial overhang on the glenoid rim was 81% positive with the arm at internal rotation whereas medial overhang was 86% negative with the arm at external rotation (P < .001). On MR arthrography, internal rotation of shoulder showed the loss of the capsulolabral buttress in all patients. CONCLUSIONS: On MR arthrography, the arthroscopically repaired capsulolabral buttress was affected by rotation of the arm after Bankart repair. Internal rotation of the arm significantly decreased our ability to see the repaired capsulolabral buttress on MR arthrography. LEVEL OF EVIDENCE: Level III, diagnostic study of nonconsecutive patients.

Adolescent↗
PubMed2004

Inter-arm asymmetry in bone mineral content and bone area in postmenopausal recreational tennis players.

OBJECTIVE: To determine whether long-term recreational tennis participation is associated with increased bone and muscle mass in the dominant compared to the non-dominant arm, in postmenopausal tennis players. METHODS: Dual-energy X-ray whole body scans were performed in 10 postmenopausal tennis players (mean +/- S.D.; 59.7 +/- 4.8 years) and 12 postmenopausal non-active women (62.8 +/- 7.2 years) matched for age and height. Tennis players started in this sport at 31.4 +/- 8.8 years, and had been playing for 26.8 +/- 6.8 years, at least 3 h per week. In addition, shoulder isokinetic muscular strength was also evaluated. RESULTS: Tennis participation resulted in a lower whole mass and fat mass in both arms (P < 0.05). Dominant arm muscle mass and shoulder joint isokinetic strength were essentially similar in both groups, however, the tennis players showed 8% greater bone mineral content and 7% greater osseous area in the dominant than in the non-dominant arm (P < 0.05). No inter-arm differences were found in bone mineral density. A relationship was observed between the length of tennis participation and the degree of inter-arm asymmetry in bone mineral content (r = 0.81, P < 0.01) and bone area (r = 0.78, P < 0.01). However, the BMD of the arms was essentially similar in both groups. No differences were observed in femoral and lumbar bone mass and density between groups. CONCLUSIONS: Long-term tennis participation is associated with increased bone mass, but not BMD, in the dominant arm of postmenopausal tennis players. The magnitude of the inter-arm asymmetry of postmenopausal tennis players is proportional to the length of tennis participation.

Absorptiometry, Photon↗
PubMed2000

Hold up of dye in the arm during fluorescein angiography: a quantitative demonstration.

PURPOSE: To demonstrate a hold-up of part of the fluorescein bolus in the arm as a result of arm position. METHOD: Case report. We obtained a fluorescein angiogram with a calibrated confocal scanning laser ophthalmoscope in a 20-year-old healthy subject. During and after injection, the upper arm was held in approximately 60 degrees abduction, 65 degrees exorotation, and slight anteflexion. In the late venous phase, the subject moved the upper arm on the injected side to a more neutral, downward position. RESULTS: We measured a distinct rise in fluorescence level about 10 seconds after movement of the arm. The most likely explanation is relief of a partial obstruction of the venous drainage, which had been caused by the position of the upper arm described above. CONCLUSION: Impaired venous drainage of the injected arm caused by exorotation and abduction of the upper arm is a potentially common cause of delayed dye arrival or unexpectedly reduced contrast level during fluorescein angiography. Therefore, arm position needs attention in fluorescein angiography.

Adult↗
PubMed2002

Scaling of peak moment arms of elbow muscles with upper extremity bone dimensions.

It is often assumed that moment arms scale with size and can be normalized by body segment lengths or limb circumferences. However, quantitative scaling relationships between moment arms and anthropometric dimensions are generally not available. We hypothesized that peak moment arms of the elbow flexor and extensor muscles scale with the shorter distance (D(s)) between the elbow flexion axis and a muscle's origin and insertion. To test this hypothesis, we estimated moment arms of six muscles that cross the elbow, digitized muscle attachment sites and bone surface geometry, and estimated the location of the elbow flexion axis in 10 upper extremity cadaveric specimens which ranged in size from a 5'0" female to a 6'4" male. D(s) accurately reflected the differences in peak moment arms across different muscles, explaining 93-99% of the variation in peaks between muscles in the same specimen. D(s) also explained between 55% and 88% of the interspecimen variation in peak moment arms for brachioradialis, biceps, and ECRL. Triceps peak moment arm was significantly correlated to the anterior-posterior dimension of the ulna measured at the olecranon (r(2)=0.61, p=0.008). Radius length provides a good measure of the interspecimen variation in peaks for brachioradialis, biceps, and ECRL. However, bone lengths were not significantly correlated to triceps moment arm or anterior-posterior bone dimensions. This work advances our understanding of the variability and scaling dimensions for elbow muscle moment arms across subjects of different sizes.

Arm↗
PubMed2003

Role of sensory information in updating internal models of the effector during arm tracking.

This chapter is divided into three main parts. Firstly, on the basis of the literature, we will shortly discuss how the recent introduction of the concept of internal models by Daniel Wolpert and Mitsuo Kawato contributes to a better understanding of what is motor learning and what is motor adaptation. Then, we will present a model of eye-hand co-ordination during self-moved target tracking, which we used as a way to specifically address these topics. Finally, we will show some evidence about the use of proprioceptive information for updating the internal models, in the context of eye-hand co-ordination. Motor and afferent information appears to contribute to the parametric adjustment (adaptation) between arm motor command and visual information about arm motion. The study reported here was aimed at assessing the contribution of arm proprioception in building (learning) and updating (adaptation) these representations. The subjects (including a deafferented subject) had to make back and forth movements with their forearm in the horizontal plane, over learned amplitude and at constant frequency, and to track an arm-driven target with their eyes. The dynamical conditions of arm movement were altered (unexpectedly or systematically) during the movement by changing the mechanical properties of the manipulandum. The results showed a significant change of the latency and the gain of the smooth pursuit system, before and after the perturbation for the control subjects, but not for the deafferented subject. Moreover, in control subjects, vibrations of the arm muscles prevented adaptation to the mechanical perturbation. These results suggest that in a self-moved target tracking task, the arm motor system shares with the smooth pursuit system an internal representation of the arm dynamical properties, and that arm proprioception is necessary to build this internal model. As suggested by Ghez et al. (1990) (Cold Spring Harbor Symp. Quant. Biol., 55: 837-8471), proprioception would allow control subjects to learn the inertial properties of the limb.

Adaptation, Physiological↗