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Carpi Radialis Muscle (carpi + radiali_muscle)
Selected AbstractsModulation of spinal inhibitory reflex responses to cutaneous nociceptive stimuli during upper limb movementEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2008Romildo Don Abstract In the present study we investigated the probability, latency and duration of the inhibitory component of the withdrawal reflex elicited by painful electrical stimulation of the index finger in humans. The stimulus consisted of a train of high-intensity pulses. The investigation was carried out in several upper limb muscles during isometric contractions of different strengths and during a motor sequence consisting of reaching, picking up and transporting an object. We used a new algorithm to detect and characterize the inhibitory reflex. The reflex was found in all muscles except the brachioradialis at all the isometric contraction strengths, and showed a distal-to-proximal gradient of latency and duration. Conversely, during movement the reflex probability was high (> 80%) in the anterior deltoid and triceps muscles during reaching, in the extensor carpi radialis muscle during transporting of the object, and in the first interosseous muscle during both picking up and transporting of the object. This modulation of inhibitory reflex transmission in the upper limb muscles suggests that the motor response is organized in such a way as to inhibit the overall ongoing motor task by interrupting motion during reaching and by releasing the object during transporting. This pattern of modulation appears to differ markedly from that previously reported for the excitatory component of the withdrawal reflex. Study of the nociceptive inhibitory reflexes during movement offers new and more profound insights into the functional anatomical organization of the spinal interneuronal network mediating sensory,motor integration. [source] Effects of endodontic instrument handle diameter on electromyographic activity of forearm and hand musclesINTERNATIONAL ENDODONTIC JOURNAL, Issue 2 2001T. Ozawa Abstract Aim To determine the influence of the handle diameter of endodontic instruments on forearm and hand muscle activity using electromyographic (EMG) recording. Methodology Size 45 K-type files were fitted with four different handle diameters; 3.5, 4.0, 5.0, and 6.0 mm. Seven dentists then attempted to negotiate to the working length acrylic resin root canals with each of the four handle sizes using a reaming motion. EMG activities were recorded from the flexor pollicis brevis muscle (f.p.b.), the flexor carpi radialis muscle (f.c.r.), and the brachioradialis muscle (b) with bipolar surface electrodes. The time taken to negotiate the canals, the area of integrated EMG that corresponded to the amount of EMG activity required during penetration and the maximum amplitude of EMG were measured using the EMG data. Results were analysed statistically using a one-way factorial anova test and multiple comparison tests. Results Reaming time and integrated EMG area of each muscle decreased with an increase in handle diameter. The most significant difference in time and area of integrated EMG was detected between handles of 6 mm and 3.5 mm diameter (time: P < 0.01, area of the f.p.b.: P < 0.01, area of the f.c.r. and b: P < 0.05), and between handles of 5 mm and 3.5 mm diameter (P < 0.05). Both 5 mm and 6 mm handles significantly decreased the maximum amplitude of EMG recorded from the f.p.b. compared with 3.5 mm handles (between 3.5 mm and 6 mm: P < 0.01, between 3.5 mm and 5 mm: P < 0.05). Conclusion The results indicate that handle diameter has an effect on reaming time as well as on muscle activity. As a consequence, handle diameter influenced operator performance during instrumentation. [source] Motor unit recruitment during lengthening contractions of human wrist flexorsMUSCLE AND NERVE, Issue 11 2001Paula J. Stotz MSc Abstract The purpose of this study was to revisit the question of recruitment of motor units during lengthening contractions because of conflicting views in the literature on this subject. Motor unit activity was recorded from the flexor carpi radialis muscle of four human subjects to compare the patterns of recruitment during lengthening and isometric contractions. Lengthening contractions were produced either when the subject voluntarily stopped opposing a background load or when an additional load was imposed on the already contracting muscle. In both cases, lengthening of the active muscle was produced at a variety of speeds, from quite slow to "as fast as possible." No differences in recruitment order were observed between isometric and lengthening contractions at any speed of lengthening contraction. It is concluded that all contractions in normal humans recruit motor units in an orderly fashion from small to large, according to the size principle of motor unit recruitment. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1535,1541, 2001 [source] Afferent-induced facilitation of primary motor cortex excitability in the region controlling hand muscles in humansEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2009H. Devanne Abstract Sensory inputs from cutaneous and limb receptors are known to influence motor cortex network excitability. Although most recent studies have focused on the inhibitory influences of afferent inputs on arm motor responses evoked by transcranial magnetic stimulation (TMS), facilitatory effects are rarely considered. In the present work, we sought to establish how proprioceptive sensory inputs modulate the excitability of the primary motor cortex region controlling certain hand and wrist muscles. Suprathreshold TMS pulses were preceded either by median nerve stimulation (MNS) or index finger stimulation with interstimulus intervals (ISIs) ranging from 20 to 200 ms (with particular focus on 40,80 ms). Motor-evoked potentials recorded in the abductor pollicis brevis (APB), first dorsalis interosseus and extensor carpi radialis muscles were strongly facilitated (by up to 150%) by MNS with ISIs of around 60 ms, whereas digit stimulation had only a weak effect. When MNS was delivered at the interval that evoked the optimal facilitatory effect, the H-reflex amplitude remained unchanged and APB motor responses evoked with transcranial electric stimulation were not increased as compared with TMS. Afferent-induced facilitation and short-latency intracortical inhibition (SICI) and intracortical facilitation (ICF) mechanisms are likely to interact in cortical circuits, as suggested by the strong facilitation observed when MNS was delivered concurrently with ICF and the reduction of SICI following MNS. We conclude that afferent-induced facilitation is a mechanism which probably involves muscle spindle afferents and should be considered when studying sensorimotor integration mechanisms in healthy and disease situations. [source] |