Abstract: Objective: To investigate the effects of moderate intensity continuous training (MICT) and high intensity intermittent training (HIIT) on the ultrastructure of myocardium and soleus in rats with high fat diet, and to explore the mechanisms. Methods: 5-week-old male SD rats were randomly divided into normal diet quiet group (C), high-fat diet quiet group (F), high-fat MICT group (M) and high-fat HIIT group (H), with 8 rats in each group, and the fat content of the high-fat dietary feed was 45%. The M and H groups were given 12 weeks of treadmill running with an incline of 25°. The M group was given continuous exercise with 70%VO₂max intensity, and the H group was given intermittent exercise with 5 min 40%~45%VO₂max and 4 min 95%~99%VO₂max intensity successively. After the intervention, the contents of free fatty acid (FFA), triglyceride (TG), high density lipoprotein cholesterol (HDL) and low density lipoprotein cholesterol (LDL) in serum were detected. Transmission electron microscopy was used to observe the ultrastructure of myocardium and soleus in rats. Western blot was used to detect the protein expressions of AMPK, malonyl-CoA decarboxylase (MCD) and carnitine palmitoyl transterase 1 (CPT-1) in myocardium and soleus. Results: Compared with C group, the body weight, Lee's index, the contents of LDL, TG and FFA in serum were increased, the content of HDL was decreased (P＜0.05), the protein expressions of AMPK and CPT-1 in myocardium and soleus were increased, the protein expression of MCD was decreased (P＜0.05), and the ultrastructure was damaged in group F. Compared with F group, the body weight and Lee's index were decreased, the contents of LDL and FFA in serum were decreased (P＜0.01), the protein expressions of AMPK, MCD and CPT-1 in myocardium were increased, and the protein expressions of AMPK and MCD in soleus were increased (P＜0.05), and the ultrastructural damage was attenuated in M and H groups. Compared with M group, the content of HDL in serum was increased (P＜0.01), the protein expressions of AMPK and MCD in myocardium were increased, and the ultrastructural damage was mild, the protein expression of AMPK in soleus was decreased, the protein expression of MCD in soleus was increased (P＜0.05), and the ultrastructural damage was severe in group H. Conclusion: MICT and HIIT have different effects on the ultrastructure of myocardium and soleus in high-fat diet rats by intervening the protein expression of AMPK, MCD and CPT-1.

Key words: moderate-intensity continuous training, high intensity interval training, myocardium, soleus, AMP-activated protein kinase, malonyl-CoA decarboxylase, carnitine palmitoyl transterase 1, rats