Effects of short-term joint immobilization in rats hindlimb muscle: metabolical and morphometrical analysis

Abstract

The aim of this work was to evaluate the effect of acute (three-day) immobilization in rats hindlimb muscles onto the metabolic and morphologic profile. Ten Wistar rats were divided into two groups (n=5 each): control group and that of immobilized limb with acrylic resin orthosis in ankle neutral position during three days. After this period, analyses made were: glycogen reserves of the soleus muscle (S), extensor digitorum longus (EDL), white gastrocnemius (WB), red gastrocnemius (RG) and tibialis anterior (TA), soleus weight, fiber area, and intramuscular connective tissue. Data were statistically treated, with significance set at p<0,05. Immobilization did not promote significant alterations in S glycogen reserves and in RG; however, there was significant reduction (of 26%) in the WG, 40% in ELD and 36% in TA. Moreover, immobilization did not promote significant reduction in S weight. The morphometric analysis showed significant reduction of the S fiber area in 31%, as well as significant increase (of 279%) in intramuscular connective tissue. It may thus be said that morphologic alterations take place during the immobilization acute phase, preceding S weight and metabolic changes. These data highlight the importance of early physical therapy intervention during the shortterm immobilization phase, aiming at minimizing skeletal muscle alterations also observed in the long term.