Locomotor changes in length and EMG activity of feline medial gastrocnemius muscle following paralysis of two synergists

H. Maas, R.J. Gregor, E.F. Hodson-Tole, B.J. Farrell, A.W. English, B.I. Prilutsky

    Research output: Contribution to JournalArticleAcademicpeer-review

    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 Xexion 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) eVects 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 signiWcantly 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 signiWcantly 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. © 2010 Springer-Verlag.
    Original languageEnglish
    Pages (from-to)681-692
    JournalExperimental Brain Research
    Volume203
    Issue number4
    DOIs
    Publication statusPublished - 2010

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    Felidae
    Paralysis
    Walking
    Skeletal Muscle
    Denervation
    Ankle
    Tendons
    Muscles
    Muscle Denervation
    Muscle Spindles
    Biomechanical Phenomena
    Cats
    Joints

    Cite this

    Maas, H. ; Gregor, R.J. ; Hodson-Tole, E.F. ; Farrell, B.J. ; English, A.W. ; Prilutsky, B.I. / Locomotor changes in length and EMG activity of feline medial gastrocnemius muscle following paralysis of two synergists. In: Experimental Brain Research. 2010 ; Vol. 203, No. 4. pp. 681-692.
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    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 Xexion 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) eVects 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 signiWcantly 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 signiWcantly 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. {\circledC} 2010 Springer-Verlag.",
    author = "H. Maas and R.J. Gregor and E.F. Hodson-Tole and B.J. Farrell and A.W. English and B.I. Prilutsky",
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    Locomotor changes in length and EMG activity of feline medial gastrocnemius muscle following paralysis of two synergists. / Maas, H.; Gregor, R.J.; Hodson-Tole, E.F.; Farrell, B.J.; English, A.W.; Prilutsky, B.I.

    In: Experimental Brain Research, Vol. 203, No. 4, 2010, p. 681-692.

    Research output: Contribution to JournalArticleAcademicpeer-review

    TY - JOUR

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    AU - Maas, H.

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    AB - 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 Xexion 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) eVects 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 signiWcantly 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 signiWcantly 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. © 2010 Springer-Verlag.

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