Rapid adjustment of sarcomere length in tenotomized muscles depends on an intact innervation.

Mean sarcomere length has been determined by laser diffraction in fibres of mouse soleus muscle at various times after division of the proximal tendon. Sarcomere length was initially reduced by 27% but was normal from 7 days after tenotomy. Initial shortening was less but recovery slower if the muscle was also denervated. Sarcomere length did not recover by 14 days if the tendon was cut soon after the muscle fibres became reinnervated after nerve section. It is suggested that afferent nervous pathways are involved in the short-term adjustment of sarcomere length to fibre length.