Changes in stiffness induced by hindlimb suspension in rat soleus muscle.
Soleus muscle atrophy was induced by hind-limb suspension of rats for 3 weeks with the intention of inducing a relative increase in the percentage of fast-twitch fibres and assessing modifications in muscle stiffness. A method of dual controlled releases was used to obtain tension/extension curves and force/velocity relationships characterizing the mechanical behaviour of the soleus. Fibre typing was achieved by myofibrillar adenosine 5'-triphosphatase staining. Results showed that hindlimb suspension decreased the percentage of slow-twitch fibres (-31%) to the profit of fast-twitch fibres (+370%) and intermediate fibres (+255%). This led to an increase in maximal shortening velocity. Tension/extension curves indicated a decrease in soleus stiffness after 3 weeks of unloading. Changes in elastic properties are interpreted in terms of modifications occurring in the active part and the passive part of the so-called series elastic component. These changes also suggest that the parameters derived from a twitch are inappropriate to account for modifications in speed-related properties of muscle.
Canon
F
F
Département de Génie Biologique, URA CNRS 858, Université de Technologie, Compiègne, France.
Goubel
F
F
D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D001835:Body Weight / Q000502:physiology; D006614:Hindlimb / Q000502:physiology*; D006651:Histocytochemistry; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018656:Muscle Fibers, Fast-Twitch / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D009929:Organ Size / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D018474:Weightlessness Simulation