The skeletal muscle has the property to adapt to different stimuli, alternating the number of sarcomeres in series, according to the length to which it is submitted to. This investigation has the aim to compare weight and length adaptations of the soleus muscle in rats, besides the total estimate of the sarcomeres in series, when submitted to intermittent stretching during immobilization in plantarflexion. Twenty-four 14 ± 2 weeks old Wistar male rats were used. They were divided in 4 groups, namely: C (n = 6) - control; A (n = 6) - stretched left soleus muscle (LSM); I (n = 6) - immobilized left soleus muscle; IA (n = 6) - immobilized and stretched LSM. The used protocol was of 3 stretching sets with 30 s duration at every 48 h, and total immobilization period of 21 days. The variations observed were compared between right soleus muscle (RSM) and LSM concerning muscular weight, muscular length and estimate of number of sarcomeres in series (ENSS), through counting in 300 mm. In the analyzed variables, when RSM (control) and LSM were compared (submitted to stretching and/or immobilization) the following were observed: muscular weight: C = -1.59% (p = 0.67); A = +5.41% (p = 0.05); I = -41.48% (p = 0.01); IA = -32.46% (p = 0.01); muscular length: C = -2.63% (p = 0.43); A = +7.54% (p = 0.07); I = -12.74% (p = 0.01); IA = -10.42% (p = 0.11); ENSS: C = -3.81% (p = 0.09); A = +2.73% (p = 0.56); I = -12.20% (p = 0.01); IA = -12.21% (p = 0.21). It is concluded that stretching during immobilization has preserved muscular length and the amount of sarcomeres in series; however, it did not prevent muscular weight loss.
Immobilization; Muscular stretching; Sarcomeres in series
