Assessment of Individual Finger Muscle Activity in the Extensor Digitorum Communis by Surface EMG

Abstract

Leijnse JN, Campbell-Kyureghyan NH, Spektor D, Quesada PM. Assessment of individual finger muscle activity in the extensor digitorum communis by surface EMG. J Neurophysiol 100: 3225-3235, 2008. First published July 23, 2008 doi:10.1152/jn.90570.2008. The extensor digitorum communis (ED) is a slender muscle group in the dorsal forearm from which tendons arise to the index (D2), medius (D3), ring (D4), and little (D5) fingers. Limited independence has been attributed to the parts that actuate the individual fingers. However, in a detailed anatomical analysis, it was found that the ED parts to the different fingers have constant and widely spaced anatomical locations that promote independent function. These observations and the superficial muscle belly locations prompted the hypothesis that these ED parts would be individually assessable by small anatomically placed surface EMG electrodes. In the present study, this hypothesis was evaluated by measuring electromyography (EMG) from the ED parts and surrounding muscles during individual finger tapping tasks with the forearm resting on a flat surface. It was found that individual ED activity can be well measured in ED2, ED3, ED4, and extensor digiti minimi (EDM). ED3 did not give nor did its electrodes receive significant crosstalk from other ED parts. ED4 electrodes recorded an EMG level of 30 Ϯ 19% (mean Ϯ SD) ED2 EMG in D2 tapping and ED2 electrodes a level of 53 Ϯ 22% ED4 EMG in D4 tapping, by hypothesis mostly crosstalk. EDM electrodes may record EMG at the level of ED4 EMG in D4 tapping. In D2 tapping, the mutual ED2 and extensor indicis redundancy reflected in large intersubject EMG differences with sometimes one or the other almost silent. The results may expand the possibilities of EMG analysis and finger muscle electrostimulation in ergonomic and clinical applications. I N T R O D U C T I O NThe extensor digitorum communis (ED) is a slender muscle complex in the dorsal forearm from which end tendons (ETs) arise to index, medius, ring, and little fingers. For the medius and ring fingers, the ED is the only extensor. The index and little fingers each have an additional extensor, the extensor indicis (EI) and extensor digiti minimi (EDM), respectively.Anatomically, the ED parts to the individual fingers are generally regarded as having limited independence. This view seems consistent with the often extensive tendinous interconnections, known as juncturae intertendinei, that exist between the ED tendons at the dorsum of the hand. These interconnections limit relative ED tendon displacements and therefore finger independence (el

Variable and Asymmetric Range of Enslaving: Fingers Can Act Independently over Small Range of Flexion

“…Furthermore, the extensor muscles might be active to minimize the enslaving movement, although subjects were instructed not to resist any natural movement in non-instructed fingers. This calls for assessing muscle activation in both agonist and antagonist muscles in further studies [9]. …”

“…This dependency of movement and force of different fingers has been termed enslaving and has been attributed to both mechanical and neural factors [1–3, 5]. Mechanical factors include epimuscular myofascial force transmission (i.e., force transmission from muscle fibers onto their surrounding connective tissue network) [6–8] and mechanical coupling between the tendons of the muscles [1–3, 9, 10]. Neural factors include drive to motor units which innervate muscles fibers located in muscle heads associated with multiple fingers, spatial overlap of motor cortex areas for movements of different fingers and diverging central commands due to projections of single motor cortex neurons to several motor neurons in the spinal cord [2, 3, 10–15].…”

Treatment of post-stroke dysphagia by vitalstim therapy coupled with conventional swallowing training

“…1.2.2 Surface Electromyography (sEMG) sEMG signals of swallowing muscles were collected through the use of Flexcomp Biomonitoring System (Thought Technology, Canada) and analyzed by using Flexcomp Infiniti software that goes with the system. After patient swallowed 2 mL of water, the maximum amplitude of sEMG signals was measured, and the average of three measurements was calculated [8][9][10] . …”

Spatial localization of electromyographic amplitude distributions associated to the activation of dorsal forearm muscles

“…One of the major causes accounted for this poor selectivity of large, surface electrodes is the high level of crosstalk (i.e., EMG signals generated by muscles different from the target one, De Luca and Merletti, 1988) that can be observed between signals recorded in multiple sites of the proximal forearm (Mogk and Keir, 2003). This issue might be limited with a careful positioning of electrode pairs (Leijnse et al, 2008a) with small inter-electrode distance (Hoffman and Strick, 1999). However, these solutions might present issues related to a number of factors, e.g., (i) inter-subject variation of muscle architecture and compartmentalization may affect the estimation of EMG activity if the electrode position is defined on the basis of anatomical references; (ii) muscle activity might not be appropriately represented if the pick-up volume of the bipolar electrodes is not big enough to collect EMG signals from a representative amount of the active motor units; (iii) detection systems with small inter-electrode distance need an accurate placement, thus the possibility to collect signals influenced by anatomical factors such as thickness of the interposed tissue and position of the innervation zone is increased.…”