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espace at MMU > Research Institutes > Institute for Biomedical Research into Human Movement and Health > Institute for Biomedical Research into Human Movement and Health > Locomotor changes in length and EMG activity of feline medial gastrocnemius muscle following paralysis of two synergists.

Please use this identifier to cite or link to this item: http://hdl.handle.net/2173/109485
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Title: Locomotor changes in length and EMG activity of feline medial gastrocnemius muscle following paralysis of two synergists.
Authors: Maas, Huub
Gregor, Robert J.
Hodson-Tole, Emma F.
Farrell, Brad J.
English, Arthur W.
Prilutsky, Boris I.
Citation: Experimental brain research, 2010, vol. 203, no. 4, pp. 681-92
Publisher: Springer
Issue Date: Jun-2010
URI: http://hdl.handle.net/2173/109485
DOI: 10.1007/s00221-010-2279-2
PubMed ID: 20458472
Additional Links: http://www.springer.com/biomed/neuroscience/journal/221
Abstract: The mechanism of the compensatory increase in electromyographic activity (EMG) of a cat ankle extensor during walking shortly after paralysis of its synergists is not fully understood. It is possible that due to greater ankle flexion in stance in this situation, muscle spindles are stretched to a greater extent and, thus, contribute to the EMG enhancement. However, also changes in force feedback and central drive may play a role. The aim of the present study was to investigate the short-term (1- to 2-week post-op) effects of lateral gastrocnemius (LG) and soleus (SO) denervation on muscle fascicle and muscle-tendon unit (MTU) length changes, as well as EMG activity of the intact medial gastrocnemius (MG) muscle in stance during overground walking on level (0%), downslope (-50%, presumably enhancing stretch of ankle extensors in stance) and upslope (+50%, enhancing load on ankle extensors) surfaces. Fascicle length was measured directly using sonomicrometry, and MTU length was calculated from joint kinematics. For each slope condition, LG-SO denervation resulted in an increase in MTU stretch and peak stretch velocity of the intact MG in early stance. MG muscle fascicle stretch and peak stretch velocity were also higher than before denervation in downslope walking. Denervation significantly decreased the magnitude of MG fascicle shortening and peak shortening velocity during early stance in level and upslope walking. MG EMG magnitude in the swing and stance phases was substantially greater after denervation, with a relatively greater increase during stance of level and upslope walking. These results suggest that the fascicle length patterns of MG muscle are significantly altered when two of its synergists are in a state of paralysis. Further, the compensatory increase in MG EMG is likely mediated by enhanced MG length feedback during downslope walking, enhanced feedback from load-sensitive receptors during upslope walking and enhanced central drive in all walking conditions.
Type: Article
Language: en
Description: The original publication is available at www.springerlink.com
Keywords: Locomotion
Proprioceptive feedback
Nerve injury
Muscle length
Muscle spindle
Plasticity
Denervation
EMG
ISSN: 1432-1106
0014-4819
Appears in Collections: Institute for Biomedical Research into Human Movement and Health

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