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Extensor Muscles (extensor + muscle)
Selected AbstractsAnatomical and Descriptive Study of the Radial Extensor Muscle (M. Extensor Carpi Radialis)ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 6 2000F. Cossu Summary The M. extensores carpi radiales have been studied in detail in humans. The aim of this study was to carry out a comparative anatomical study of these muscles using four species , rabbit, cat, dog and sheep , and to propose a ,systematization' in a few standard models according to the morphological variations seen. In these species, there is marked morphological evolution, with two muscles in humans, one in sheep and a more or less distinct division of the muscle in the rabbit, cat and dog. Examination of the vascularization and nerve supply enables us to determine degrees of division in species with similar muscle morphology. Thus we were able to distinguish three morphological types which allow us to infer the morphological evolution of the M. extensores carpi radiales and to estimate the point at which one muscle became two. However, there is a strong chance that some process of convergence may have occurred, and in pentadactyl species many elements represent the plesiomorphis and are therefore of little use in constructing a classification on the basis of evolution. [source] Functional anatomy and muscle moment arms of the pelvic limb of an elite sprinting athlete: the racing greyhound (Canis familiaris)JOURNAL OF ANATOMY, Issue 4 2008S. B. Williams Abstract We provide quantitative anatomical data on the muscle,tendon architecture and geometry of the pelvic limb of an elite sprint athlete, the racing greyhound. Specifically, muscle masses, muscle lengths, fascicle lengths, pennation angles and muscle moment arms were measured. Maximum isometric force and power of muscles, the maximum muscle torque at joints and tendon stress and strain were estimated. We compare data with that published for a generalized breed of canid, and other cursorial mammals such as the horse and hare. The pelvic limb of the racing greyhound had a relatively large volume of hip extensor muscle, which is likely to be required for power production. Per unit body mass, some pelvic limb muscles were relatively larger than those in less specialized canines, and many hip extensor muscles had longer fascicle lengths. It was estimated that substantial extensor moments could be created about the tarsus and hip of the greyhound allowing high power output and potential for rapid acceleration. The racing greyhound hence possesses substantial specializations for enhanced sprint performance. [source] The effect of strength training on the force of twitches evoked by corticospinal stimulation in humansACTA PHYSIOLOGICA, Issue 2 2009T. J. Carroll Abstract Aim:, Although there is considerable evidence that strength training causes adaptations in the central nervous system, many details remain unclear. Here we studied neuromuscular responses to strength training of the wrist by recording electromyographic and twitch responses to transcranial magnetic stimulation (TMS) and cervicomedullary stimulation of the corticospinal tract. Methods:, Seventeen participants performed 4 weeks (12 sessions) of strength training for the radial deviator (RD) muscles of the wrist (n = 8) or control training without external load (n = 9). TMS recruitment curves were constructed from stimuli at five to eight intensities ranging between 15% below resting motor threshold and maximal stimulator output, both at rest and during isometric wrist extension (EXT) and RD at 10% and 50% of maximal voluntary contraction (MVC). Responses to weak TMS and cervicomedullary stimulation (set to produce a response of 10% maximal M wave amplitude during 10% MVC EXT contraction) were also compared at contraction strengths ranging from 10% to 75% MVC. Results:, Isometric strength increased following strength training (10.7% for the RD MVC, 8.8% for the EXT MVC), but not control training. Strength training also significantly increased the amplitude of TMS- and cervicomedullary-evoked twitches during low-force contractions. Increases in the force-generating capacity of the wrist extensor muscles are unlikely to account for this finding because training did not affect the amplitude of twitches elicited by supra-maximal nerve stimulation. Conclusion:, The data suggest that strength training induces adaptations that increase the net gain of corticospinal-motor neuronal projections to the trained muscles. [source] Therapeutic effects of functional electrical stimulation of the upper limb of eight children with cerebral palsyDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 11 2000P A Wright BSc PhD Functional electrical stimulation (FES) of the upper limb has been used for patients with a variety of neurological conditions, although few studies have been conducted on its use on the upper limb of children with cerebral palsy (CP). The aim of this study was to investigate the effect of cyclic FES on the wrist extensor muscles of a group of eight children (five boys, three girls) with hemiplegic CP (mean age 10 years). The study design involved a baseline (3 weeks), treatment (6 weeks), and follow-up (6 weeks). FES was applied for 30 minutes daily during the treatment period of the study. Improvements in hand function (p,0.039) and active wrist extension (p=0.031) were observed at the end of the treatment period. These improvements were largely maintained until the end of the follow-up period. No significant change was observed in the measurements of wrist extension moment during the treatment period (p=0.274). Hand function in this group of children improved after they were exposed to FES of wrist extensor muscles. This suggests that FES could become a useful adjunct therapy to complement existing management strategies available for this patient population. [source] Differential maturation of motoneurons innervating ankle flexor and extensor muscles in the neonatal ratEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2000L Vinay Abstract The first postnatal week is a critical period for the development of posture in the rat. The use of ankle extensor muscles in postural reactions increases during this period. Changes in excitability of motoneurons are probably an important factor underlying this maturation. The aim of this study was to identify whether variations in the maturation exist between motor pools innervating antagonistic muscles. Intracellular recordings in the in vitro brain stem,spinal cord preparation of neonatal rats (from postnatal day 0,5) were used to examine the developmental changes in excitability of motoneurons innervating the ankle flexors (F-MNs) and the antigravity ankle extensors (E-MNs). No significant difference in resting potential, action potential threshold, input resistance or rheobase was observed at birth. The age-related increase in rheobase was more pronounced for F-MNs than for E-MNs. The development of discharge properties of E-MNs lagged behind that of F-MNs. More F-MNs than E-MNs were able to fire repetitively in response to current injection at birth. F-MNs discharged at a higher frequency than E-MNs at all ages. Differences in the duration of action potential afterhyperpolarization accounted, at least partly, for the differences in discharge frequency between E-MNs and F-MNs at birth, and for the age-related increase in firing rate. These results suggest that E-MNs are more immature at birth than F-MNs and that there is a differential development of motoneurons innervating antagonistic muscles. This may be a critical factor in the development of posture and locomotion. [source] Human jaw muscle strength and size in relation to limb muscle strength and sizeEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 5 2004M. C. Raadsheer The aim of the present study was to investigate to what extent general factors (e.g. genotype, hormones) and factors at the craniofacial level (e.g. craniofacial size, jaw muscle architecture) contribute to the size and strength of the jaw muscles. A strong relationship of jaw muscle size and strength with that of other muscles would argue for general influences, whereas a weak relationship would argue for craniofacial influences. In 121 adult individuals, moments of maximal bite force, arm flexion force and leg extension force were measured. In addition, thicknesses of jaw muscles, arm flexor muscles and leg extensor muscles were measured using ultrasound. Relationships were assessed by using a principal component analysis. In females, one component was found in which all force moments were represented. Bite force moment, however, loaded very low. In males, two components were found. One component loaded for arm flexion and leg extension moments, the other loaded for bite force moments. In both females and males, only one component was found for the muscle thicknesses in which all muscle groups loaded similarly. It was concluded that the size of the jaw muscles was significantly related to the size of the limb muscles, suggesting that they were both subject to the same general influences. Maximal voluntary bite force moments were not significantly related to the moments of the arm flexion and leg extension forces, suggesting that besides the general influence on the muscle size, variation in bite force moment was also influenced by local variables, such as craniofacial morphology. [source] Functional anatomy and muscle moment arms of the pelvic limb of an elite sprinting athlete: the racing greyhound (Canis familiaris)JOURNAL OF ANATOMY, Issue 4 2008S. B. Williams Abstract We provide quantitative anatomical data on the muscle,tendon architecture and geometry of the pelvic limb of an elite sprint athlete, the racing greyhound. Specifically, muscle masses, muscle lengths, fascicle lengths, pennation angles and muscle moment arms were measured. Maximum isometric force and power of muscles, the maximum muscle torque at joints and tendon stress and strain were estimated. We compare data with that published for a generalized breed of canid, and other cursorial mammals such as the horse and hare. The pelvic limb of the racing greyhound had a relatively large volume of hip extensor muscle, which is likely to be required for power production. Per unit body mass, some pelvic limb muscles were relatively larger than those in less specialized canines, and many hip extensor muscles had longer fascicle lengths. It was estimated that substantial extensor moments could be created about the tarsus and hip of the greyhound allowing high power output and potential for rapid acceleration. The racing greyhound hence possesses substantial specializations for enhanced sprint performance. [source] Bradykinesia, muscle weakness and reduced muscle power in Parkinson's disease,MOVEMENT DISORDERS, Issue 9 2009Natalie E. Allen BAppSc (Physio) Hons Abstract Muscle power (force × velocity) could clarify the relationship between weakness and bradykinesia in Parkinson's disease (PD). The aims of this study were to determine if patients with PD were weaker and/or less powerful in their leg extensor muscles than a neurologically normal control group and to determine the relative contributions of force and movement velocity/bradykinesia to muscle power in PD. Forty patients with PD and 40 controls were assessed. Strength in Newtons (N) was measured as the heaviest load the participant could lift. Power in Watts (W) was measured by having the participant perform lifts as fast as possible. The PD group were 172 N weaker (95% CI 28,315) and 124 W less powerful at peak power (95% CI 32,216) than controls. However, velocity at maximal power was only reduced compared with controls when lifting light to medium loads. When lifting heavy loads bradykinesia was no longer apparent in the PD group. These results suggest that reduced muscle power in PD at lighter loads arises from weakness and bradykinesia combined, but at heavier loads arises only from weakness. The absence of bradykinesia in the PD group when lifting heavy loads warrants further investigation. © 2009 Movement Disorder Society [source] Impaired heteronymous somatosensory motor cortical inhibition in dystoniaMOVEMENT DISORDERS, Issue 11 2003Laura Bertolasi MD Abstract A typical pathophysiological abnormality in dystonia is cocontraction of antagonist muscles, with impaired reciprocal inhibitory mechanisms in the spinal cord. Recent experimental data have shown that inhibitory interactions between antagonist muscles have also a parallel control at the level of the sensorimotor cortex. The aim of this work was to study heteronymous effects of a median nerve stimulus on the corticospinal projections to forearm muscles in dystonia. We used the technique of antagonist cortical inhibition, which assesses the conditioning effect of median nerve afferent input on motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) in ipsilateral forearm extensor muscles at rest. Nine healthy subjects and 10 patients with torsion dystonia participated in the study. MEPs and somatosensory evoked potentials were normal in patients. In healthy subjects, median nerve stimulation at 15- to 18-msec intervals inhibited the test MEPs in forearm extensors. In dystonic patients, median nerve stimulation delivered at the same conditioning,test intervals elicited significantly less inhibition of the test MEP. On the whole, these data suggest an impaired sensory,motor integration in dystonia and, more specifically, the decreased antagonistic cortical inhibition could suggest that functional interactions between antagonist muscles are primarily impaired at the cortical level. © 2003 Movement Disorder Society [source] Comparative Analysis of Muscle Architecture in Primate Arm and ForearmANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 2 2010Yasuhiro Kikuchi With 7 figures and 3 tables Summary A comparative study of myological morphology, i.e. muscle mass (MM), muscle fascicle length and muscle physiological cross-sectional area (an indicator of the force capacity of muscles), was conducted in nine primate species: human (Homo sapiens), chimpanzee (Pan troglodytes), gibbon (Hylobates spp.), papio (Papio hamadryas), lutong (Trachypithecus francoisi), green monkey (Chlorocebus aethiops), macaque monkey (Macaca spp.), capuchin monkey (Cebus albifrons) and squirrel monkey (Saimiri sciureus). The MM distributions and the percentages in terms of functional categories were calculated as the ratios of the muscle masses. Moreover, individual normalized data were compared directly amongst species, independent of size differences. The results show that the different ratios of forearm-rotation muscles between chimpanzee and gibbons may be related to the differences in their main positional behaviour, i.e. knuckle-walking in chimpanzees and brachiation in gibbons, and the different frequencies of arm-raising locomotion between these two species. Moreover, monkeys have larger normalized MM values for the elbow extensor muscles than apes, which may be attributed to the fact that almost all monkeys engage in quadrupedal locomotion. The characteristics of the muscle internal parameters of ape and human are discussed in comparison with those of monkey. [source] Reliability of knee extension and flexion measurements using the Con-Trex isokinetic dynamometerCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 6 2007Nicola A. Maffiuletti Summary The aim of this study was to evaluate the reliability of isokinetic and isometric assessments of the knee extensor and the flexor muscle function using the Con-Trex isokinetic dynamometer. Thirty healthy subjects (15 males, 15 females) were tested and retested 7 days later for maximal strength (isokinetic peak torque, work, power and angle of peak torque as well as isometric maximal voluntary contraction torque and rate of torque development) and fatigue (per cent loss and linear slope of torque and work across a series of 20 contractions). For both the knee extensor and the flexor muscle groups, all strength data , except angle of peak torque , demonstrated moderate-to-high reliability, with intraclass correlation coefficients (ICC) higher than 0·86. The highest reliability was observed for concentric peak torque of the knee extensor muscles (ICC = 0·99). Test,retest reliability of fatigue variables was moderate for the knee extensor (ICC range 0·84,0·89) and insufficient-to-moderate for the knee flexor muscles (ICC range 0·78,0·81). The more reliable index of muscle fatigue was the linear slope of the decline in work output. These findings establish the reliability of isokinetic and isometric measurements using the Con-Trex machine. [source] | |||||||||||||