Effect of Eight Weeks of Resistance Training on PAX7 and MyoD in Fast and Slow-Twitch Skeletal Muscles of Old Rats

Background: Box 7 protein (PAX7) and myogenic differentiation (MyoD) proteins are the essential proteins to regulate the satellite cell and muscle hypertrophy. Objectives: We aimed to investigate the effect of resistance training (RT) on PAX7 and MyoD in soleus and extensor digitorum longus (EDL) muscles of old rats. Methods: In this experimental study, 12 old female rats were randomly divided into two groups including RT and control groups. The RT program was three days a week for eight weeks, in which the rats climbed a one-meter vertical ladder with 26 steps. The carried weights varied from 50% of body weight in the first week to 100% of body weight in the 8th week. Kolmogorov- Smirnov test and independent sample t test was used for statistical analysis (P≤0.05). Results: MyoD protein in RT group significantly increased in soleus and EDL muscles compared with the control group (P = 0.001). Also, Pax7 significantly increased in the soleus muscle in the RT group compared with control group (P = 0.002); nevertheless, there was no significant difference in Pax7 protein in the EDL muscle between the RT and control groups (P = 0.10). Conclusion: RT can lead to proliferation and renewal of satellite cells in the soleus and EDL muscles by increasing PAX7 and MyoD proteins.