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This Article Full Text Full Text (PDF) All Versions of this Article: 553/3/925    most recent jphysiol.2003.048389v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Giroux-Metges, M.-A. Articles by Gioux, M. Search for Related Content PubMed PubMed Citation Articles by Giroux-Metges, M.-A. Articles by Gioux, M.

Motor unit properties in the soleus muscle after its distal tendon transfer to the plantaris muscle tendon in the rat

Marie-Agnès Giroux-Metges*, Jean-Pierre Pennec*, Julien Petit†, Christelle Goanvec*, Germaine Dorange‡ and Maxime Gioux*

The aim of this study was to evaluate how a modification in the mechanical conditions under which a muscle is used could induce changes in the characteristics and the spinal drive of its motor units (MU). The distal tendon of the soleus muscle of Wistar rats was transferred to the distal stump of the plantaris muscle tendon. The EMG activity of the soleus was chronically recorded for 8 weeks, every other day, during a 1-min treadmill walk. After spinal ventral root splitting, individual MU contractile properties were measured in control soleus (102 MUs) or in transposed soleus muscles after 4 weeks (41 MUs) or 8 weeks (28 MUs). Muscle/body weight ratio did not vary after transposition, nor did MU tetanic forces. A decrease in MU twitch contraction times and in their half relaxation times was observed at weeks 4 and 8. MU tension-frequency curves varied significantly after tendon transfer, becoming closer to the curves of the fast MUs of the control group. During locomotion, we observed no change in the amplitude of rectified-filtered electromyographic activity, but a significant decrease in mean burst duration and an increase in the median frequency of the power density spectrum. Tendon transposition of the soleus muscle brought about adaptations in MU contractile properties and soleus spinal control.