Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology
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J Electromyogr Kinesiol · Dec 2005
Randomized Controlled TrialThe effect of postural correction on muscle activation amplitudes recorded from the cervicobrachial region.
In clinical practice, postural correction is a common treatment approach for individuals with neck and shoulder pain. As chronic static muscle use is thought to be associated with the onset of some neck and shoulder pain syndromes, it is important to understand the impact a postural correction program might have on muscle activation amplitudes in the neck and shoulder regions. Normalized surface electromyographic data were recorded from the levator scapulae, upper trapezius, supraspinatus, posterior deltoid, masseter, rhomboid major, cervical erector spinae, and sternocleidomastoid muscles of the dominant side of each of eighteen healthy subjects. ⋯ Corrected posture in sitting did, however produce a statistically significant reduction in muscle activity compared to forward head posture. Corrected posture in standing required more muscle activity than habitual or forward head posture in the majority of cervicobrachial and jaw muscles, suggesting that a graduated approach to postural correction exercises might be required in order to train the muscles to appropriately withstand the requirements of the task. A surprising finding was that muscle activity levels and postural changes had the largest impact on the masseter muscle, which demonstrated activation levels in the order of 20% maximum voluntary electrical activation.
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J Electromyogr Kinesiol · Oct 2005
The effects of interelectrode distance on electromyographic amplitude and mean power frequency during isokinetic and isometric muscle actions of the biceps brachii.
The purpose of this study was to examine the effects of interelectrode distance (IED) on the absolute and normalized electromyographic (EMG) amplitude and mean power frequency (MPF) versus isokinetic and isometric torque relationships for the biceps brachii muscle. Ten adults [mean+/-SD age=22.0+/-3.4 years] performed submaximal to maximal, isokinetic and isometric muscle actions of the dominant forearm flexors. Following determination of isokinetic peak torque (PT) and the isometric maximum voluntary contraction (MVC), the subjects performed randomly ordered, submaximal step muscle actions in 10% increments from 10% to 90% PT and MVC. ⋯ These findings suggested that for the biceps brachii muscle, IEDs between 20 and 60mm resulted in similar patterns for the EMG amplitude or MPF versus dynamic and isometric torque relationships. Furthermore, unlike the absolute EMG amplitude and MPF values, the normalized EMG data were not influenced by changes in IED between 20 and 60mm. Thus, normalized EMG data can be compared among previous studies that have utilized different IED arrangements.
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J Electromyogr Kinesiol · Jun 2004
Comparative StudyThe cross-correlation and phase-difference methods are not equivalent under noninvasive estimation of the motor unit propagation velocity.
Noninvasive estimation of motor unit propagation velocity (MUPV) was reduced to that of the time delay between signals detected by two surface EMG electrodes placed along the muscle fibres. When the cross-correlation function between the signals was used, the problem with temporal resolution arose. Estimation of the time delay in the frequency domain was proposed to overcome this problem. ⋯ The longitudinal double difference electrodes were preferable with the phase-difference method, while the MUPV estimates obtained by the cross-correlation technique were more correct when the longitudinal single difference or bipolar transversal double difference electrodes were used. In addition, the estimates obtained by the phase-difference method were more sensitive to the longitudinal scattering of motor end-plates and ends of the fibres, to the fibre lengths and to the negative after-potential magnitude. Such sensitivity could make MUPV estimates incorrect even under a relatively small distance between the motor unit axis and electrode.
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J Electromyogr Kinesiol · Feb 2004
ReviewFrom confounders to suspected risk factors: psychosocial factors and work-related upper extremity disorders.
Psychosocial variables have recently been more prominent among epidemiologic risk factors for work-related upper extremity disorders (WRUEDs), but bio-behavioral mechanisms underlying these associations have been elusive. One reason is that the psychosocial domain has included many broad and disparate variables (e.g. mood, coping skills, job control, job satisfaction, job stress, social support), and this lack of specificity in the conceptualization of psychosocial factors has produced limited hypothesis testing opportunities. Therefore, recent research efforts have focused on identifying and conceptualizing specific psychosocial factors that might more clearly delineate plausible bio-behavioral mechanisms linking psychosocial factors to WRUEDs. ⋯ An initial self-report measure of workstyle has been pilot tested among office workers and shown acceptable reliability and validity. Future studies are needed to study this construct among other working populations and to determine its relationship with other clinical endpoints. Nevertheless, early findings suggest workstyle may be a potential focus of WRUED prevention efforts.
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J Electromyogr Kinesiol · Feb 2004
ReviewMechanisms of central sensitization, neuroimmunology & injury biomechanics in persistent pain: implications for musculoskeletal disorders.
This review will offer an overview of the mechanistic pathways of chronic pain associated with musculoskeletal disorders (MSDs). Traditional electrophysiological pain pathways of these injuries will be reviewed. In addition, recent research efforts in persistent pain have characterized a cascade of neuroimmunologic events in the central nervous system that manifests in pain behaviors and neurochemical nociceptive responses. ⋯ This painful syndrome will be used as an example to provide a context for presenting immune mechanisms of chronic pain and their relationship to injury. Measures of injury biomechanics are presented in the context of the resulting pain responses, including behavioral sensitivity, local structural changes, and cellular and molecular changes in the CNS. Lastly, based on these findings and others, a discussion is provided highlighting areas of future work to help elucidate methods of injury diagnosis and development of therapeutic treatments.