Effect of previous strength training episodes and retraining on cross-sectional area and protein contents of rat soleus muscle

Abstract

PURPOSE: This study tested the hypothesis that previous strength training episodes favorably contribute to muscular hypertrophic adaptations in rat soleus muscle after long-term detraining and retraining in rats. METHODS: Female Sprague-Dawley rats (n=24) aged 8 weeks were randomly assigned to four groups: Control (CON), detraining (DT), strength training (ST), and retraining (RT). The strength training was a regular bout of ladder climbing exercise that consisted of three sets of five repetitions and three days per week for eight weeks. A cylinder containing weights was loaded to the bottom of each rat’s tail. The weights carried during each training session were initially 50% of body weight and progressively increased by 10% per session. Rats in the DT underwent twenty weeks of detraining periods immediately after eight weeks of strength training. Rats in the ST were aged matched to the RT group and underwent eight weeks of strength training at the same duration with the RT group. Rats in the RT were conducted to the resistance training for eight weeks following the detraining period. Soleus muscles were collected at the end of the training episodes to examine alterations in cross-sectional area and protein contents. RESULTS: ST showed a significant increase in cross-sectional area of the rat soleus muscle, compared with CON. It was interestingly demonstrated that RT markedly elicited hypertrophy of soleus muscle, compared with all other groups. It was supported that RTinduced hypertrophy was related to increased myofibrillar protein contents of the soleus muscle. CONCLUSIONS: These results suggest that although prolonged training cessation occurs previous strength training episodes have a positive impact on restoring muscular contractile properties and hypertrophy after retraining. ? 2020 Korean Society of Exercise Physiology.