Flexors

Distribution by Scientific Domains
Distribution within Life Sciences

Kinds of Flexors

  • elbow flexor
  • knee flexor
  • plantar flexor
  • wrist flexor

  • Terms modified by Flexors

  • flexor digitorum muscle
  • flexor halluci longu
  • flexor muscle
  • flexor tendon

  • Selected Abstracts


    Differential age-related changes in motor unit properties between elbow flexors and extensors

    ACTA PHYSIOLOGICA, Issue 1 2010
    B. H. Dalton
    Abstract Aim:, Healthy adult ageing of the human neuromuscular system is comprised of changes that include atrophy, weakness and slowed movements with reduced spinal motor neurone output expressed by lower motor unit discharge rates (MUDRs). The latter observation has been obtained mostly from hand and lower limb muscles. The purpose was to determine the extent to which elbow flexor and extensor contractile properties, and MUDRs in six old (83 ± 4 years) and six young (24 ± 1 years) men were affected by age, and whether any adaptations were similar for both muscle groups. Methods:, Maximal isometric voluntary contraction (MVC), voluntary activation, twitch contractile properties, force,frequency relationship and MUDRs from sub-maximal to maximal intensities were assessed in the elbow flexors and extensors. Results:, Both flexor and extensor MVCs were significantly (P < 0.05) less (,42% and ,46% respectively) in the old than in the young. Contractile speeds and the force,frequency relationship did not show any age-related differences (P > 0.05). For the elbow flexors contraction duration was ,139 ms and for the extensors it was ,127 ms for both age groups (P > 0.05). The mean MUDRs from 25% MVC to maximum were lower (,10% to ,36%) in the old than in the young (P < 0.01). These age-related differences were larger for biceps (Cohen's d = 8.25) than triceps (Cohen's d = 4.79) brachii. Conclusion:, Thus, at least for proximal upper limb muscles, mean maximal MUDR reductions with healthy adult ageing are muscle specific and not strongly related to contractile speed. [source]


    Orthopaedic issues in the musculoskeletal care of adults with cerebral palsy

    DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 2009
    HELEN M HORSTMANN MD
    Aims, Orthopaedic care of adults with cerebral palsy (CP) has not been well documented in orthopaedic literature. This paper focuses on some of the common problems which present themselves when adults with CP seek orthopaedic intervention. In particular, we review the most common orthopaedic issues which present to the Penn Neuro-Orthopaedics Program. Method, A formal review of consecutive surgeries performed by the senior author on adults with CP was previously conducted. This paper focuses on the health delivery care for the adult with orthopaedic problems related to cerebral palsy. Ninety-two percent of these patients required lower extremity surgery. Forty percent had procedures performed on the upper extremities. Results, The majority of problems seen in the Penn Neuro-Orthopaedics Program are associated with the residuals of childhood issues, particularly deformities associated with contractures. Patients are also referred for treatment of acquired musculoskeletal problems such as degenerative arthritis of the hip or knee. A combination of problems contribute most frequently to foot deformities and pain with weight-bearing, shoewear or both, most often due to equinovarus. The surgical correction of this is most often facilitated through a split anterior tibial tendon transfer. Posterior tibial transfers are rarely indicated. Residual equinus deformities contribute to a pes planus deformity. The split anterior tibial tendon transfer is usually combined with gastrocnemius-soleus recession and plantar release. Transfer of the flexor digitorum longus to the os calcis is done to augment the plantar flexor power. Rigid pes planus deformity is treated with a triple arthrodesis. Resolution of deformity allows for a good base for standing, improved ability to tolerate shoewear, and/or braces. Other recurrent or unresolved issues involve hip and knee contractures. Issues of lever arm dysfunction create problems with mechanical inefficiency. Upper extremity intervention is principally to correct contractures. Internal rotation and adductor tightness at the shoulder makes for difficult underarm hygiene and predispose a patient to a spiral fracture of the humerus. A tight flexor, pronation pattern is frequently noted through the elbow and forearm with further flexion contractures through the wrist and fingers. Lengthenings are more frequently performed than tendon transfers in the upper extremity. Arthrodesis of the wrist or on rare occasions of the metacarpal-phalangeal joints supplement the lengthenings when needed. Conclusions, The Penn Neuro-Orthopaedics Program has successfully treated adults with both residual and acquired musculoskeletal deformities. These deformities become more critical when combined with degenerative changes, a relative increase in body mass, fatigue, and weakness associated with the aging process. [source]


    Superficial digital flexor tendon lesions in racehorses as a sequela to muscle fatigue: A preliminary study

    EQUINE VETERINARY JOURNAL, Issue 6 2007
    M. T. Butcher
    Summary Reasons for performing study: Racing and training related lesions of the forelimb superficial digital flexor tendon are a common career ending injury to racehorses but aetiology and/or predisposing causes of the injury are not completely understood. Objectives: Although the injury takes place within the tendon, the lesion must be considered within the context of the function of the complete suspensory system of the distal limb, including the associated muscles. Methods: Both muscle and tendon function were investigated in vivo using implanted strain gauges in 3 Thoroughbred horses walking, trotting and cantering on a motorised treadmill. These data were combined with assessments of muscle architecture and fibre composition to arrive at an overview of the contribution of each muscle-tendon unit during locomotion. Results: The superficial digital flexor muscle has fatigue-resistant and high force production properties that allow its tendon to store and return elastic energy, predominantly at the trot. As running speed increases, deep digital flexor tendon force increases and it stabilises hyperextension of the fetlock, thus reinforcing the superficial digital flexor in limb load support. The deep digital flexor muscle has fast contracting properties that render it susceptible to fatigue. Conclusion: Based on these measurements and supporting evidence from the literature, it is proposed that overloading of the superficial digital flexor tendon results from fatigue of the synergistic, faster contracting deep digital flexor muscle. Potential relevance: Future research investigating distal limb system function as a whole should help refine clinical diagnostic procedures and exercise training approaches that will lead to more effective prevention and treatment of digital flexor tendon injuries in equine athletes. [source]


    The pathophysiology of spasticity

    EUROPEAN JOURNAL OF NEUROLOGY, Issue 2002
    G. Sheean
    Spasticity is only one of several components of the upper motor neurone (UMN) syndrome, known collectively as the `positive' phenomena, that are characterized by muscle overactivity. Other components include tendon hyper-reflexia, clonus, the clasp-knife phenomenon, flexor and extensor spasms, a Babinski sign, and spastic dystonia. Spasticity is a form of hypertonia due to hyperexcitable tonic stretch reflexes. It is distinguished from rigidity by its dependence upon the speed of the muscle stretch and by the presence of other positive UMN signs. Hyperactive spinal reflexes mediate most of these positive phenomena, while others are due to disordered control of voluntary movement or abnormal efferent drive. An UMN lesion disturbs the balance of supraspinal inhibitory and excitatory inputs, producing a state of net disinhibition of the spinal reflexes. These include proprioceptive (stretch) and nociceptive (flexor withdrawal and extensor) reflexes. The clinical syndrome resulting from an UMN lesion depends more upon its location and extent, and the time since it occurred, than on the pathology of the lesion. However, the change in spinal reflex excitability cannot simply be due to an imbalance in supraspinal control. The delayed onset after the lesion and the frequent reduction in reflex excitability over time, suggests plasticity in the central nervous system. Knowledge of the electrophysiology and neurochemistry of spinal reflexes, together with the action of antispasticity drugs, helps us to understand the pathophysiology of spasticity. [source]


    Corticospinal control of antagonistic muscles in the cat

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2007
    Christian Ethier
    Abstract We recently suggested that movement-related inter-joint muscle synergies are recruited by selected excitation and selected release from inhibition of cortical points. Here we asked whether a similar cortical mechanism operates in the functional linking of antagonistic muscles. To this end experiments were done on ketamine-anesthetized cats. Intracortical microstimulation (ICMS) and intramuscular electromyographic recordings were used to find and characterize wrist, elbow and shoulder antagonistic motor cortical points. Simultaneous ICMS applied at two cortical points, each evoking activity in one of a pair of antagonistic muscles, produced co-contraction of antagonistic muscle pairs. However, we found an obvious asymmetry in the strength of reciprocal inhibition; it was always significantly stronger on physiological extensors than flexors. Following intravenous injection of a single bolus of strychnine, a cortical point at which only a physiological flexor was previously activated also elicited simultaneous activation of its antagonist. This demonstrates that antagonistic corticospinal neurons are closely grouped, or intermingled. To test whether releasing a cortical point from inhibition allows it to be functionally linked with an antagonistic cortical point, one of three GABAA receptor antagonists, bicuculline, gabazine or picrotoxin, was injected iontophoretically at one cortical point while stimulation was applied to an antagonistic cortical point. This coupling always resulted in co-contraction of the represented antagonistic muscles. Thus, antagonistic motor cortical points are linked by excitatory intracortical connections held in check by local GABAergic inhibition, with reciprocal inhibition occurring at the spinal level. Importantly, the asymmetry of cortically mediated reciprocal inhibition would appear significantly to bias muscle maps obtained by ICMS in favor of physiological flexors. [source]


    Differential maturation of motoneurons innervating ankle flexor and extensor muscles in the neonatal rat

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2000
    L 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]


    Low Serum Vitamin D Does Not Predict New Disability or Loss of Muscle Strength in Older Women

    JOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 5 2002
    René Verreault MD
    OBJECTIVES: To determine whether serum levels of 25-hydroxyvitamin D (25(OH)D) and parathyroid hormone (PTH) predict accelerated decline in muscular strength or onset of new disability in mobility and upper extremity functioning over a 3-year follow-up. DESIGN: A community-based prospective cohort study. PARTICIPANTS: Six hundred twenty-eight moderately to severely disabled women aged 65 and older living in the community. MEASUREMENTS: Subjects were divided into three groups of baseline 25(OH)D serum levels (deficiency: <25 nmol/L; low normal: 25,52 nmol/L; high normal: ,53 nmol/L) and into tertiles of PTH levels. Objective performance measures (hip flexor, knee extensor, and grip strengths; walking speed; and time for repeated chair stands) and disability in activities involving mobility and upper extremity function were assessed at baseline and every 6 months for 3 years. Decline in performance measures and onset of new disability were compared between 25(OH)D and PTH groups using random effects models and proportional hazards models, respectively, while adjusting for age, race, education, body mass index, baseline performance, and chronic conditions. RESULTS: The annual rate of decline over 3 years in muscular strength, walking speed, and time to perform repeated chair stands was similar across 25(OH)D groups. We observed a nonsignificantly faster decline in proximal muscle strength and walking speed with increasing PTH levels. There was no association for either measure between serum levels and the risk of incident disability in activities relating to mobility and upper extremity function. CONCLUSION: This study does not support the hypothesis that vitamin D deficiency is associated with loss in muscular strength and decline in mobility and upper extremity functioning over time in older women who were moderately to severely disabled at baseline. [source]


    Fibre type composition of the human psoas major muscle with regard to the level of its origin

    JOURNAL OF ANATOMY, Issue 6 2009
    Juraj Arbanas
    Abstract The aim of our study was to explore the fibre type composition of the human psoas major muscle at different levels of its origin, from the first lumbar to the fourth lumbar vertebra, and to compare the muscle fibre size and distribution of different fibre types between levels with respect to its complex postural and dynamic function. Muscle samples were collected from 15 young males (younger than 35 years). Serial transverse sections (5 ,m) of the samples were cut by cryomicrotome. Type I, IIA and IIX muscle fibres were typed using myosin heavy chain identification. The serial sections were analysed using a light microscope with a magnitude of 100×. The differences between measurements were evaluated using a repeated-measures anova and Scheffé test for post-hoc analysis. Our study showed that the human psoas major muscle was composed of type I, IIA and IIX muscle fibres. It had a predominance of type IIA muscle fibres, whereas type I muscle fibres had the largest cross-sectional area. Type IIX muscle fibres were present as a far smaller percentage and had the smallest cross-sectional area. Moreover, the fibre type composition of the psoas major muscle was different between levels of its origin starting from the first lumbar to the fourth lumbar vertebra. We conclude that the fibre type composition of the psoas major muscle indicated its dynamic and postural functions, which supports the fact that it is the main flexor of the hip joint (dynamic function) and stabilizer of the lumbar spine, sacroiliac and hip joints (postural function). The cranial part of the psoas major muscle has a primarily postural role, whereas the caudal part of the muscle has a dynamic role. [source]


    Impact of gravity loading on post-stroke reaching and its relationship to weakness

    MUSCLE AND NERVE, Issue 2 2007
    Randall F. Beer PhD
    Abstract The ability to extend the elbow following stroke depends on the magnitude and direction of torques acting at the shoulder. The mechanisms underlying this link remain unclear. The purpose of this study was to evaluate whether the effects of shoulder loading on elbow function were related to weakness or its distribution in the paretic limb. Ten subjects with longstanding hemiparesis performed movements with the arm either passively supported against gravity by an air bearing, or by activation of shoulder muscles. Isometric maximum voluntary torques at the elbow and shoulder were measured using a load cell. The speed and range of elbow extension movements were negatively impacted by actively supporting the paretic limb against gravity. However, the effects of gravity loading were not related to proximal weakness or abnormalities in the elbow flexor,extensor strength balance. The findings support the existence of abnormal descending motor commands that constrain the ability of stroke survivors to generate elbow extension torque in combination with abduction torque at the shoulder. Muscle Nerve, 2007 [source]


    Intraspinally mediated state-dependent enhancement of motoneurone excitability during fictive scratch in the adult decerebrate cat

    THE JOURNAL OF PHYSIOLOGY, Issue 15 2010
    Kevin E. Power
    This is the first study to report on the increase in motoneurone excitability during fictive scratch in adult decerebrate cats. Intracellular recordings from antidromically identified motoneurones revealed a decrease in the voltage threshold for spike initiation (Vth), a suppression of motoneurone afterhyperpolarization and activation of voltage-dependent excitation at the onset of scratch. These state-dependent changes recovered within 10,20 s after scratch and could be evoked after acute transection of the spinal cord at C1. Thus, there is a powerful intraspinal system that can quickly and reversibly re-configure neuronal excitability during spinal network activation. Fictive scratch was evoked in spinal intact and transected decerebrate preparations by stroking the pinnae following topical curare application to the dorsal cervical spinal cord and neuromuscular block. Hyperpolarization of Vth occurred (mean ,5.8 mV) in about 80% of ipsilateral flexor, extensor or bifunctional motoneurones during fictive scratch. The decrease in Vth began before any scratch-evoked motoneurone activity as well as during the initial phase in which extensors are tonically hyperpolarized. The Vth of contralateral extensors depolarized by a mean of +3.7 mV during the tonic contralateral extensor activity accompanying ipsilateral scratch. There was a consistent and substantial reduction of afterhyperpolarization amplitude without large increases in motoneurone conductance in both spinal intact and transected preparations. Depolarizing current injection increased, and hyperpolarization decreased the amplitude of rhythmic scratch drive potentials in acute spinal preparations indicating that the spinal scratch-generating network can activate voltage-dependent conductances in motoneurones. The enhanced excitability in spinal preparations associated with fictive scratch indicates the existence of previously unrecognized, intraspinal mechanisms increasing motoneurone excitability. [source]


    Endogenous extracellular serotonin modulates the spinal locomotor network of the neonatal mouse

    THE JOURNAL OF PHYSIOLOGY, Issue 1 2010
    Mary J. Dunbar
    Serotonin (5-HT) can potently activate and modulate spinal locomotor circuits in a variety of species. Many of these findings have been obtained by applying serotonin exogenously to the isolated spinal cord of in vitro preparations, which has the drawback of indiscriminately activating extrasynaptic receptors and neurons. To investigate the role of endogenously released serotonin in modulating locomotor networks, the selective serotonin reuptake inhibitor citalopram was used. Fictive locomotion was elicited by either electrical stimulation of the brainstem or the sacral 4 (S4) dorsal root. The addition of 20 ,m of citalopram caudal to thoracic segment 5 (T5) had an overall inhibitory effect on the lumbar central pattern generator (CPG). Left,right and flexor,extensor coupling were significantly decreased, and there was also a phase shift in the flexor,extensor relationship. In addition, there was a significant decrease in burst amplitude. These effects were observed during both afferent and brainstem evoked fictive locomotion. When citalopram was added in the presence of 5-HT1A and 5-HT1B antagonists, the inhibitory effects were largely reversed. The remaining excitatory effects were mediated by 5-HT7 and 5-HT2 receptors. These results suggest that endogenous 5-HT release can modulate locomotor-like activity early in neonatal development. [source]


    Jaccoud's arthropathy in systemic lupus erythematosus: Differentiation of deforming and erosive patterns by magnetic resonance imaging

    ARTHRITIS & RHEUMATISM, Issue 1 2003
    Benedikt Ostendorf
    Objective To evaluate alterations of the soft tissues, tendons, and bones as detected by magnetic resonance imaging (MRI) in patients with systemic lupus erythematosus (SLE),associated arthritis of the finger joints. Methods Both hands of 14 patients with SLE of various activities and durations and with arthritis and/or deformities of the finger joints were examined by MRI and conventional radiography. Coronal T1-weighted spin-echo (with and without gadolinium contrast), axial T2-weighted turbo spin-echo, coronal fat-suppressed short tau inversion recovery, and 3-dimensional double-echo steady-state sequences were acquired and analyzed, and the findings were compared with those from conventional radiographs. Results MRI detected periarticular capsular swelling in all 14 patients, joint effusion in 7, edematous tenosynovitis in 6, proliferative tenosynovitis (flexor and/or extensor tendons) in 4, and intraarticular signs of synovial membrane hypertrophy in 10 patients, 9 of whom showed enhancement after administration of contrast medium. Bony erosions were identified in 8 patients by MRI; conventional radiography missed these erosions in 2 of the 8 patients. Four of the 14 patients were designated as Jaccoud's arthropathy index,positive, and all 4 showed severe edematous tenosynovitis and capsular swelling, but no signs of bony erosions despite longstanding disease (mean 21.5 years). Four of the 10 patients with mild deformity exhibited prominent soft tissue pathology, with minimal destruction of bone; the other 6 patients had bony alterations that resembled rheumatoid arthritis. Conclusion In SLE patients with arthritis of the finger joints, MRI detects characteristic signs of soft tissue pathology (e.g., capsular swelling, edematous and proliferative tenosynovitis, synovial hypertrophy) and bony alterations (e.g., erosions, some of which are missed by conventional radiography). MRI thus helps to distinguish different types of lupus arthritis/Jaccoud's arthropathy, which allows more differentiated treatment strategies and monitoring. [source]


    The contribution of the palmaris longus muscle to the strength of thumb abduction

    CLINICAL ANATOMY, Issue 4 2010
    Hope Gangata
    Abstract The palmaris longus muscle (PLM) is described as a weak flexor of the wrist and a tensor of the palmar aponeurosis, but not a thumb abductor. The PLM is believed to aid thumb abduction through its insertion onto the thenar eminence. Two groups, both right hand dominant, were selected from 1,200 sampled participants. The first group comprised of 38 subjects with unilateral presence of the PLM and was used to determine the strength of thumb abduction. The second group comprised of 30 subjects, with bilateral presence of the PLM, and it was used to calculate the effects of hand dominance. A significant number of subjects with bilateral absence of the PLM were observed and undocumented. Using a dynamometer in subjects with unilateral presence of the PLM, the force of thumb abduction was significantly greater on the hand with a PLM than the one without it (P = 0.014), irrespective of hand dominance. In the second sample with bilateral PLM, thumb abduction on the dominant hand was 10% stronger than on the nondominant hand and was similar to the universally accepted average of 10% increase in grip strength of the dominant hand. Thus, 10% was deducted from all the dominant hands, and the force of thumb abduction remained greater on the hand with PLM than the hand without it (P = 0.049). The results of this study demonstrated the PLM to be involved in thumb abduction, and the authors therefore recommend that this action of the muscle be universally accepted by anatomists and hand surgeons. Clin. Anat. 23:431,436, 2010. © 2010 Wiley-Liss, Inc. [source]


    The frequency of absence of palmaris longus in a South African population of mixed race

    CLINICAL ANATOMY, Issue 4 2010
    Robert Ndou
    Abstract The palmaris longus (PL) is a weak flexor of the wrist that may be harvested as a tendon graft and used in surgical procedures for reconstructive purposes. The PL is congenitally absent in 15% of the worldwide population. However, the frequency of absence varies considerably among different population groups, being as high as 63.9% in the Turkish population and as low as 3% in the black population in the Republic of Congo. In this study, South African persons of mixed race (n = 201) were assessed by two anatomists for the presence of the PL tendon using three clinical tests, namely the Traditional Test, Mishra's Test II, and the Gangata Test. The most reliable of the three tests used was determined using Kendall's coefficient of concordance. Of the total number of subjects used, 11.5% had absence (either bilaterally or unilaterally) of the PL tendon. There was a 5.5% bilateral absence of the PL. The study revealed that the PL tendon may present in six different patterns according to the clinical assessment tests applied, the presence or absence of the PL alongside the flexor capi radialis, and the degree of prominence of PL, if present. Using the Kendall's coefficient of concordance, the Mishra's Test II, and the Gangata Test, both involving abduction of the thumb, were found to be most effective in revealing the PL. The frequency of absence of the PL in South Africans of mixed race has been determined. Clin. Anat. 23:437,442, 2010. © 2010 Wiley-Liss, Inc. [source]


    A case of an accessory brachialis muscle

    CLINICAL ANATOMY, Issue 6 2006
    Marios Loukas
    Abstract Functionally, the brachialis muscle serves a critical role as the primary flexor of the arm at the elbow. However, few reports exist in the literature, which describe variations of this muscle. We present a case of an accessory brachialis muscle (AcBr), found during routine dissection at Harvard Medical School during 2003. The AcBr originated medially from the mid-shaft of the humerus and the medial intermuscular septum. During its course medially, toward the elbow, the AcBr crossed both the brachial artery and the median nerve. The distal tendon split to surround the median nerve before inserting into the common tendon of the antebrachial flexor compartment muscles. Embryological origins and clinical considerations including median nerve entrapment are considered. Clin. Anat. 19:550,553, 2006. © 2005 Wiley-Liss, Inc. [source]


    Differential age-related changes in motor unit properties between elbow flexors and extensors

    ACTA PHYSIOLOGICA, Issue 1 2010
    B. H. Dalton
    Abstract Aim:, Healthy adult ageing of the human neuromuscular system is comprised of changes that include atrophy, weakness and slowed movements with reduced spinal motor neurone output expressed by lower motor unit discharge rates (MUDRs). The latter observation has been obtained mostly from hand and lower limb muscles. The purpose was to determine the extent to which elbow flexor and extensor contractile properties, and MUDRs in six old (83 ± 4 years) and six young (24 ± 1 years) men were affected by age, and whether any adaptations were similar for both muscle groups. Methods:, Maximal isometric voluntary contraction (MVC), voluntary activation, twitch contractile properties, force,frequency relationship and MUDRs from sub-maximal to maximal intensities were assessed in the elbow flexors and extensors. Results:, Both flexor and extensor MVCs were significantly (P < 0.05) less (,42% and ,46% respectively) in the old than in the young. Contractile speeds and the force,frequency relationship did not show any age-related differences (P > 0.05). For the elbow flexors contraction duration was ,139 ms and for the extensors it was ,127 ms for both age groups (P > 0.05). The mean MUDRs from 25% MVC to maximum were lower (,10% to ,36%) in the old than in the young (P < 0.01). These age-related differences were larger for biceps (Cohen's d = 8.25) than triceps (Cohen's d = 4.79) brachii. Conclusion:, Thus, at least for proximal upper limb muscles, mean maximal MUDR reductions with healthy adult ageing are muscle specific and not strongly related to contractile speed. [source]


    Myotonic dystrophy: muscle involvement in relation to disease type and size of expanded CTG-repeat sequence

    DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 7 2005
    Anna-Karin Kroksmark PT Msc
    This study aimed to: classify a cohort of children and adolescents with myotonic dystrophy (dystrophia myotonica: DM) into congenital and childhood onset forms; estimate CTG expansion size; and quantify muscle strength, contractures, and motor function in children with DM and compare results with those of controls. Participants were clinically examined, medical records were reviewed, and isometric muscle strength, contractures, and motor function were measured. Participants were: 42 children with DM (18 females, 24 males; mean age 8y 9mo [SD 4y 7mo], range 10mo to 17y) and 42 age- and sex-matched, healthy controls. Children with DM were divided into three groups: severe congenital (n=13), mild congenital (n=15), and childhood (n=14). Children with childhood DM were significantly weaker than controls (wrist and ankle dorsiflexors [p=0.0044, p=0.0044 respectively]; hip abductors and flexors [p=0.0464, p=0.0217]; and knee flexors and extensors: [p=0.0382, p=0.0033]). Children with mild congenital DM were significantly weaker than controls in all assessed muscle groups Contractures and skeletal deformities were more frequent at time of investigation than at birth, suggesting that foot and spine deformities in particular increase over time. Motor function score was significantly lower for children with DM than for controls. Children with severe congenital DM had the lowest motor function, with correlation between motor function and size of CTG repeat (p=-0.743). Children found jumping, heel standing, and head lifting the most difficult items to perform but few had difficulty walking, running, or stair climbing. DM in children is a heterogeneous disorder with a wide spectrum of muscle involvement, and owing to increased risk of contractures and skeletal deformities, regular follow-ups are recommended. [source]


    Relation between spasticity and strength in individuals with spastic diplegic cerebral palsy

    DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 3 2002
    Sandy A Ross MHS PT PCS
    The relation between spasticity and strength in individuals with cerebral palsy (CP) has not been extensively researched. Knee and ankle spasticity and strength were quantified in a retrospective analysis of 60 individuals with spastic diplegic CP (mean age 12 years, range 3 to 38) and a group of 50 individuals without disabilities (WD group; mean age 12 years, range 4 to 36). Spasticity was measured using a KinCom dynamometer that stretched the passive knee flexors or ankle plantarflexors at different speeds and recorded the amount of resistive torques. For the strength tests, the participant performed a maximum contraction of the knee flexors/extensors and ankle plantarflexors/dorsiflexors throughout their range of motion at a speed of 10/s on the dynamometer. Pearson's correlation coefficient was used to determine if a relation existed between spasticity and strength within the same muscle group and in opposing muscle groups at the knee and ankle joints. A t-test was performed to determine if greater spasticity and less strength existed at the ankles compared with the knees in those with CP. Results show that there was no relation between spasticity and strength either within the same muscle group or at opposing muscle groups at the knee and ankle joints in persons with CP. Individuals with spastic diplegic CP were more involved (greater spasticity, less strength) distally at the ankles compared with the knees. The findings conflict with the literature, which contains several assumptions, one of which is that a spastic muscle is a strong muscle and that spasticity causes weakness in the opposing muscle group. We found no relation between spasticity and strength in individuals with CP. Our findings support the literature, which states that individuals with spastic diplegic CP are more involved distally compared with proximally in the lower extremities. [source]


    Computerized Tremor Analysis of Valproate-induced Tremor: A Comparative Study of Controlled-release versus Conventional Valproate

    EPILEPSIA, Issue 2 2005
    Martina Rinnerthaler
    Summary:,Purpose: Valproate (VPA) induces postural tremor in 6,45% of patients. The characteristics of VPA-induced tremor have not yet been quantitatively assessed, and it is not known whether tremor prevalence or severity is affected by VPA formulation (controlled-release CR-VPA vs. conventional VPA). The aim of this study was quantitatively to assess tremor in epilepsy patients receiving VPA and to compare the effects of two VPA formulations (CR-VPA vs. VPA) on tremor severity. Methods: In a prospective study, 18 consecutive patients with newly diagnosed focal or generalized epilepsy were assigned to receive alternately either VPA (n = 10) or CR-VPA (n = 8) monotherapy. Computerized tremor analysis was performed at baseline 1 day before initiating VPA treatment and repeated after a seizure-free period of ,8 weeks, during which VPA doses had remained stable. Rest and postural tremor were recorded by accelerometry, and surface electromyograms (EMGs) were recorded from the wrist flexors and extensors. Results: At baseline, the two groups had similar postural tremor amplitudes. At follow-up, the CR-VPA group had remained at the same level, whereas VPA subjects exhibited a significant increase in tremor amplitudes (p < 0.05) despite comparable VPA doses and comparable plasma VPA concentrations at the time of tremor testing. Conclusions: This is the first study to assess quantitatively VPA-induced tremor by standardized tremor analysis. These results suggest that CR-VPA may cause less tremorigenic activity as compared with standard VPA. The mechanisms underlying this difference are unclear but may include greater peak,trough variation with VPA than with CR-VPA. [source]


    Corticospinal control of antagonistic muscles in the cat

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2007
    Christian Ethier
    Abstract We recently suggested that movement-related inter-joint muscle synergies are recruited by selected excitation and selected release from inhibition of cortical points. Here we asked whether a similar cortical mechanism operates in the functional linking of antagonistic muscles. To this end experiments were done on ketamine-anesthetized cats. Intracortical microstimulation (ICMS) and intramuscular electromyographic recordings were used to find and characterize wrist, elbow and shoulder antagonistic motor cortical points. Simultaneous ICMS applied at two cortical points, each evoking activity in one of a pair of antagonistic muscles, produced co-contraction of antagonistic muscle pairs. However, we found an obvious asymmetry in the strength of reciprocal inhibition; it was always significantly stronger on physiological extensors than flexors. Following intravenous injection of a single bolus of strychnine, a cortical point at which only a physiological flexor was previously activated also elicited simultaneous activation of its antagonist. This demonstrates that antagonistic corticospinal neurons are closely grouped, or intermingled. To test whether releasing a cortical point from inhibition allows it to be functionally linked with an antagonistic cortical point, one of three GABAA receptor antagonists, bicuculline, gabazine or picrotoxin, was injected iontophoretically at one cortical point while stimulation was applied to an antagonistic cortical point. This coupling always resulted in co-contraction of the represented antagonistic muscles. Thus, antagonistic motor cortical points are linked by excitatory intracortical connections held in check by local GABAergic inhibition, with reciprocal inhibition occurring at the spinal level. Importantly, the asymmetry of cortically mediated reciprocal inhibition would appear significantly to bias muscle maps obtained by ICMS in favor of physiological flexors. [source]


    Differential maturation of motoneurons innervating ankle flexor and extensor muscles in the neonatal rat

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2000
    L 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]


    Evidence from proprioception of fusimotor coactivation during voluntary contractions in humans

    EXPERIMENTAL PHYSIOLOGY, Issue 3 2008
    Trevor J. Allen
    In experiments on position sense at the elbow joint in the horizontal plane, blindfolded subjects were required to match the position of one forearm (reference) by placement of their other arm (indicator). Position errors were measured after conditioning elbow muscles of the reference arm with an isometric contraction while the arm was held either flexed or extended. The difference in errors after the two forms of conditioning was large when the conditioned muscles remained relaxed during the matching process and it became less when elbow muscles were required to lift a load during the match (10 and 25% of maximal voluntary contraction, respectively). Errors from muscle conditioning were attributed to signals arising in muscle spindles and were hypothesized to result from the thixotropic property of passive intrafusal fibres. Active muscle does not exhibit thixotropy. It is proposed that during a voluntary contraction the errors after conditioning are less, because the spindles become coactivated through the fusimotor system. The distribution of errors is therefore seen to be a reflection of fusimotor recruitment thresholds. For elbow flexors most, but not all, fusimotor fibres appear to be recruited by 10% of a maximal contraction. [source]


    Exercise Heat Stress does not Reduce Central Activation to non-exercised Human Skeletal Muscle

    EXPERIMENTAL PHYSIOLOGY, Issue 6 2003
    Julian Saboisky
    In this study we measured the central activation ratio (CAR) of the leg extensors and the elbow flexor muscles before and after exhaustive exercise in the heat to determine whether exercise-induced hyperthermia affects the CNS drive to exercised (leg extensors) and/or non-exercised (forearm flexors) muscle groups. Thirteen subjects exercised at fixed intensities representative of a percentage of peak power output (PPO) for 10 min periods (50%, 40%, 60%, 50%) and then at 75% PPO until exhaustion in ambient conditions of 39.3 ± 0.8 °C and 60.0 ± 0.8% relative humidity. Before and immediately following exercise subjects performed a series of maximal voluntary contractions (MVCs) with the leg extensors (exercised muscles) and forearm flexors (non-exercised muscles). The degree of voluntary activation during the sustained MVCs was assessed by superimposing electrical stimulation to the femoral nerve and the biceps brachii. Exercise to exhaustion increased the rectal temperature from 37.2 ± 0.2 to 38.8 ± 0.2 °C (P < 0.0001). The mean heart rate at the end of exercise to exhaustion was 192 ± 3 beats min,1. Leg extensor voluntary force was significantly reduced from 595 ± 143 to 509 ± 105 N following exercise-induced hyperthermia but forearm flexor force was similar before and after exercise. The CAR of the leg extensors decreased from 94.2 ± 1.3% before exercise to 91.7 ± 1.5% (P < 0.02) following exercise-induced hyperthermia. However, the CAR for the forearm flexors remained at similar levels before and after exercise. The data suggest that the central nervous system selectively reduces central activation to specific skeletal muscles as a consequence of exercise-induced hyperthermia. [source]


    Contractile Properties, Fatigue and Recovery are not Influenced by Short-Term Creatine Supplementation in Human Muscle

    EXPERIMENTAL PHYSIOLOGY, Issue 4 2000
    J. M. Jakobi
    There have been several studies on the effect of short-term creatine (Cr) supplementation on exercise performance, but none have investigated both voluntary and stimulated muscle contractions in the same experiment. Fourteen moderately active young men (19-28 years) were randomly assigned, in a double blind manner, to either a creatine (Cr) or placebo (P) group. The subjects supplemented their regular diet 4 times a day for 5 days with either 5 g Cr + 5 g maltodextrin (Cr group), or 5 g maltodextrin (P group). Isometric maximal voluntary contraction (MVC), muscle activation, as assessed using the modified twitch interpolation technique, electrically stimulated contractile properties, electromyography (EMG), endurance time and recovery from fatigue were measured in the elbow flexors. The fatigue protocol involved both voluntary and stimulated contractions. Following supplementation there was a significant weight gain in the Cr group (1.0 kg), whereas the P group did not change. For each group, pre-supplementation measures were not significantly different from post-supplementation for MVC, twitch and tetanic tensions at rest, time to peak tension, half-relaxation time and contraction duration. Prior to Cr supplementation time to fatigue was 10 ± 4 min (mean ± S.E.M.) for both groups, and following supplementation there was a non-significant increase of 1 min in each group. MVC force, muscle activation, EMG, stimulated tensions and durations were similar for the Cr and P groups over the course of the fatigue protocol and did not change after supplementation. Furthermore, recovery of MVC, stimulated tensions and contractile speeds did not differ as a result of Cr supplementation. These results indicate that short-term Cr supplementation does not influence isometric elbow flexion force, muscle activation, stimulated contractile properties, or delay time to fatigue or improve recovery. [source]


    Impact of low cost strength training of dorsi- and plantar flexors on balance and functional mobility in institutionalized elderly people

    GERIATRICS & GERONTOLOGY INTERNATIONAL, Issue 1 2009
    Fernando Ribeiro
    Aim: To evaluate the effects of a low cost strength training program of the dorsi- and ankle plantar flexors on muscle strength, balance and functional mobility, in elderly institutionalized subjects; and to determine the association between strength gain and balance and/or functional mobility gain. Methods: Forty-eight volunteers were recruited and equally divided into two groups: intervention (aged 78.44 ± 3.84 years) and control (aged 79.78 ± 3.90 years). Both groups were tested at baseline and outcome for ankle dorsi- and plantar flexors muscle strength, balance and functional mobility. The intervention group participated in a 6-week program, three-sessions-per-week, of resisted ankle dorsi- and plantar flexion exercises using elastic bands. Results: In the intervention group, maximal isometric dorsi- (from 8.4 ± 0.45 to 12.6 ± 0.95 kg; P , 0.001) and plantar flexors strength (from 13.0 ± 0.85 to 17.5 ± 0.93 kg; P , 0.001), balance (from 14.6 ± 0.54 to 22.3 ± 1.81 cm; P , 0.001) and functional mobility (from 18.4 ± 0.51 to 11.0 ± 0.66 s; P , 0.001) increased significantly after the 6-week strength training program. In the control group, no significant differences were detected. In the intervention group, a significant correlation between plantar flexor strength gain and balance gain was found (r = 0.826; P = 0.01). Conclusion: The proposed low cost strength training of dorsi- and plantar flexors improved strength, balance and functional mobility in institutionalized elderly people; moreover, the improvement in plantar flexor strength was associated with the improvement in balance. [source]


    Improving functional magnetic resonance imaging motor studies through simultaneous electromyography recordings

    HUMAN BRAIN MAPPING, Issue 9 2007
    Bradley J. MacIntosh
    Abstract Specially designed optoelectronic and data postprocessing methods are described that permit electromyography (EMG) of muscle activity simultaneous with functional MRI (fMRI). Hardware characterization and validation included simultaneous EMG and event-related fMRI in 17 healthy participants during either ankle (n = 12), index finger (n = 3), or wrist (n = 2) contractions cued by visual stimuli. Principal component analysis (PCA) and independent component analysis (ICA) were evaluated for their ability to remove residual fMRI gradient-induced signal contamination in EMG data. Contractions of ankle tibialis anterior and index finger abductor were clearly distinguishable, although observing contractions from the wrist flexors proved more challenging. To demonstrate the potential utility of simultaneous EMG and fMRI, data from the ankle experiments were analyzed using two approaches: 1) assuming contractions coincided precisely with visual cues, and 2) using EMG to time the onset and offset of muscle contraction precisely for each participant. Both methods produced complementary activation maps, although the EMG-guided approach recovered more active brain voxels and revealed activity better in the basal ganglia and cerebellum. Furthermore, numerical simulations confirmed that precise knowledge of behavioral responses, such as those provided by EMG, are much more important for event-related experimental designs compared to block designs. This simultaneous EMG and fMRI methodology has important applications where the amplitude or timing of motor output is impaired, such as after stroke. Hum Brain Mapp 2006. © 2006 Wiley-Liss, Inc. [source]


    Muscle Strength After Resistance Training Is Inversely Correlated with Baseline Levels of Soluble Tumor Necrosis Factor Receptors in the Oldest Old

    JOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 2 2004
    Helle Bruunsgaard MD
    Objectives:, To test the hypothesis that physical exercise induces an antiinflammatory response that is associated with reduced chronic activation of the tumor necrosis factor (TNF)-alpha system in frail elders and that the increase in muscle strength after resistance training is limited by systemic low-grade inflammation. Design:, A 12-week controlled resistance-training study. Setting:, Nursing homes in Copenhagen, Denmark. Participants:, Twenty-one frail nursing home residents aged 86 to 95 completed the study. Intervention:, Ten participants were randomized to a program of resistance training of knee extensors and flexors three times a week for 12 weeks; the remaining 11 participants served as a control group who joined social activities supervised by an occupation therapist. Measurements:, Muscle strength, plasma levels of TNF-,, soluble TNF receptor (sTNFR)-1, and interleukin (IL)-6 were measured before and at the end of the intervention period. Results:, The training program improved muscle strength but did not affect plasma levels of TNF-, and sTNFR-I or IL-6. However, plasma levels of sTNFR-I at baseline were inversely correlated with the increase in muscle strength. Conclusion:, Low-grade activation of the TNF system could limit the increase in muscle strength after resistance training in the oldest old. Furthermore, data suggest that theantiinflammatory response induced by 12 weeks of resistance training is not sufficient to reduce chronic activation of the TNF system, but the small sample size limited this interpretation. [source]


    The Relationship Between Lower Body Strength and Obstructed Gait in Community-Dwelling Older Adults

    JOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 3 2002
    Ecosse L. Lamoureux PhD
    OBJECTIVES: To determine the relationship between lower body strength of community-dwelling older adults and the time to negotiate obstructed gait tasks. DESIGN: A correlational study. SETTING: The Biomechanics Laboratory, Deakin University, Australia. PARTICIPANTS: Twenty-nine women and 16 men aged 62 to 88 were recruited using advertisements placed in local newspapers. The participants were independent community dwellers, healthy and functionally mobile. MEASUREMENTS: Maximal isometric strength of the knee extensors and dynamic strength of the hip extensors, hip flexors, hip adductors, hip abductors, knee extensors, knee flexors, and ankle plantar flexors were assessed. The times to negotiate four obstructed gait tasks at three progressively challenging levels on an obstacle course and to complete the course were recorded. The relationship between strength and the crossing times was explored using linear regression models. RESULTS: Significant associations between the seven strength measures and the times to negotiate each gait task and to walk the entire course at each level were obtained (r = ,0.38 to ,0.55; P < .05). In addition, the percentage of the variance explained by strength (R2), consistently increased as a function of the progressively challenging level. This increase was particularly marked for the stepping over task (R2 = 19.3%, 25.0%, and 27.2%, for levels 1, 2, and 3, respectively) and the raised surface condition (R2 = 17.1%, 21.1%, and 30.8%, for levels 1, 2, and 3, respectively). CONCLUSION: The findings of the study showed that strength is a critical requirement for obstructed locomotion. That the magnitude of the association increased as a function of the challenging levels suggests that intervention programs aimed at improving strength would potentially be effective in helping community-dwelling older adults negotiate environmental gait challenges. J Am Geriatr Soc 50:468,473, 2002. [source]


    Mechanical constraints on the functional morphology of the gibbon hind limb

    JOURNAL OF ANATOMY, Issue 4 2009
    Anthony J. Channon
    Abstract Gibbons utilize a number of locomotor modes in the wild, including bipedalism, leaping and, most of all, brachiation. Each locomotor mode puts specific constraints on the morphology of the animal; in some cases these may be complementary, whereas in others they may conflict. Despite several studies of the locomotor biomechanics of gibbons, very little is known about the musculoskeletal architecture of the limbs. In this study, we present quantitative anatomical data of the hind limb for four species of gibbon (Hylobates lar, H. moloch, H. pileatus and Symphalangus syndactylus). Muscle mass and fascicle lengths were obtained from all of the major hind limb muscles and the physiological cross-sectional area was calculated and scaled to remove the effect of body size. The results clearly indicate that, for all of the species studied, the major hip, knee and ankle extensors are short-fascicled and pennate. The major hip and knee flexors, however, are long-fascicled, parallel muscles with relatively small physiological cross-sectional areas. We hypothesize that the short-fascicled muscles could be coupled with a power-amplifying mechanism and are predominantly useful in leaping. The long-fascicled knee and hip flexors are adapted for a wide range of joint postures and can play a role in flexing the legs during brachiation. [source]


    Morphology and function of the forelimb in arboreal frogs: specializations for grasping ability?

    JOURNAL OF ANATOMY, Issue 3 2008
    Adriana S. Manzano
    Abstract Frogs are characterized by a unique morphology associated with their saltatory lifestyle. Although variation in the form and function of the pelvic girdle and associated appendicular system related to specialized locomotor modes such as swimming or burrowing has been documented, the forelimbs have typically been viewed as relatively unspecialized. Yet, previous authors have noted versatility in forelimb function among arboreal frogs associated with feeding. Here we study the morphology and function of the forelimb and hand during locomotion in two species of arboreal frogs (Litoria caerulea and Phyllomedusa bicolor). Our data show a complex arrangement of the distal forelimb and hand musculature with some notable differences between species. Analyses of high-speed video and video fluoroscopy recordings show that forelimbs are used in alternating fashion in a diagonal sequence footfall pattern and that the position of the hand is adjusted when walking on substrates of different diameters. Electromyographic recordings show that the flexors of the hand are active during substrate contact, suggesting the use of gripping to generate a stabilizing torque. Measurements of grasping forces in vivo and during stimulation experiments show that both species, are capable of executing a so-called power grip but also indicates marked differences between species, in the magnitude of forces generated. Stimulation experiments showed an increased control of digit flexion in the more specialized of the two species, allowing it to execute a precision grip paralleled only by that seen in primates. [source]