As one exercise program of cardiac rehabilitation, the role of high-intensity interval training (HIIT) in improving myocardial infarction is still controversial, and the mechanism is unclear.

To investigate the effect of HIIT on improving the cardiac structure and function in a rat model of myocardial infarction.

An experiment was conducted from September 2020 to October 2021. From a random sample of 78 3-month-old male SD rats, 56 were eventually included, and 14 of them were randomly selected as sham-surgery group (Sham group) , and the remaining 42 rats were equally randomized into MI-sedentary group (MI-SED group) , MI-HIIT group (MI-HIIT group) , and MI-medium-intensity continuous training (MI-MICT group) after being used for preparing a model of acute myocardial infarction (AMI) . Sham group and MI-SED group were not trained, MI-HIIT group received high-intensity and medium-intensity training alternately, MI-MICT group received medium-intensity continuous training. After 1 week of AMI modeling, MI-HIIT and MI-MICT groups received 8 weeks of training. At the end of 4 weeks of training, 7 rats in each of the 4 groups were randomly selected for detecting cardiac ultrasound, and weighing body weight, then were sacrificed, and their heart weight and serum tumor necrosis factor (TNF-α) were measured, cardiac mass index was calculated, and heart tissues were measured using H&E staining, Masson's Trichrome staining and immunohistochemical staining. At the end of 8 weeks of training, the same operation was performed on the remaining 7 rats in each of the groups.

After 4 weeks of training, the standardized cardiac mass index of MI-HIIT group was higher than that of each of the other three groups (P<0.05) . The sham group had higher ejection fraction (EF) , fractional shortening (FS) and left ventricular end-systolic posterior wall thickness (LVPWs) than MI-HIIT and MI-MICT groups (P<0.05) . MI-SED group had lower EF, FS, and LVPWs, and higher left ventricular end-systolic diameter (LVESD) than MI-HIIT and MI-MICT groups (P<0.05) . After 8 weeks of training, MI-HIIT group had lower body weight than sham and MI-SED groups, higher heart weight than sham, MI-SED and MI-MICT groups, and higher standardized cardiac mass index than sham and MI-MICT groups (P<0.05) . MI-HIIT group demonstrated higher EF, LVESD, left ventricular end-diastolic diameter (LVEDD) , left ventricular end-systolic anterior wall thickness (LVAWs) than sham and MI-SED groups (P<0.05) . Moreover, MI-HIIT group also showed higher FS and LVPWs than MI-SED group (P<0.05) . HE staining results showed that MI-HIIT group had significantly improved inflammatory changes of heart tissue and more closely arranged myocardial cells at the end of the 8th week of training compared with at the end of 4 weeks of training. Masson's Trichrome staining results showed that after 8 weeks of training, the proportion of myocardial fibrillar collagen in myocardial tissues of MI-SED group was higher than that of MI-HIIT and MI-MICT groups. Immunohistochemical results showed that MI-HIIT group had more newly formed blood vessels in cardiac tissues than sham and MI-SED groups after 4 and 8 weeks of training, so did the MI-MICT group. The number of newly formed blood vessels in cardiac tissues of MI-HIIT group was more than that in MI-MICT group after 8 weeks of training. MI-HIIT group had higher serum TNF-α than MI-SED group after 4 weeks of training. After 8 weeks of training, the serum TNF-α in MI-HIIT group was higher than that in MI-MICT group.

HIIT performed in the early stage of AMI could improve cardiac mass index, induce early inflammatory response in myocardial tissue, reduce myocardial fibrosis, promote angiogenesis and ventricular remodeling. HIIT had better overall effect than MICT.

高强度间歇训练（HIIT）作为心脏康复的运动方案之一，对于心肌梗死的作用还存在争议，且作用机制尚不明确。

探讨HIIT对心肌梗死大鼠心脏结构和功能的影响。

于2020年9月至2021年10月，随机选取3月龄雄性SD大鼠共78只，最终纳入研究56只。随机选取14只为假手术组（Sham组），其余大鼠制备急性心肌梗死（AMI）模型后随机分为心梗静息组（MI-SED组，n=14）、心梗HIIT组（MI-HIIT组，n=14），心梗中等强度持续训练（MICT）组（MI-MICT组，n=14）。Sham组与MI-SED组不进行训练，MI-HIIT组高强度与中等强度训练交替进行，MI-MICT组进行中等强度持续训练。AMI大鼠建模1周后MI-HIIT、MI-MICT组开始进行训练，训练4周后，四组分别随机取7只大鼠进行心脏超声检测，称量体质量（BW）、心脏质量（HW），计算心脏质量指数（HMI），检测血清肿瘤坏死因子α（TNF-α）水平，并取心脏组织进行HE染色、Masson染色及免疫组化分析；训练8周后对四组剩余7只大鼠采集数据和样本进行相同试验处理。

训练4周后MI-HIIT组标准化HMI高于Sham组、MI-SED组和MI-MICT组（P<0.05）；训练8周后MI-HIIT组最终BW低于Sham组和MI-SED组，HW高于Sham组、MI-SED组和MI-MICT组，标准化HMI高于Sham组和MI-MICT组（P<0.05）。训练4周后，MI-HIIT组和MI-MICT组射血分数（EF）、缩短分数（FS）、左心室收缩末期后壁厚度（LVPWs）低于Sham组，高于MI-SED组（P<0.05）；MI-HIIT组和MI-MICT组左心室收缩末期内径（LVDs）低于MI-SED组（P<0.05）。训练8周后，MI-HIIT组EF、LVDs、左心室舒张末期内径（LVDd）、左心室收缩末期前壁厚度（LVAWs）高于Sham组和MI-SED组，FS、LVPWs高于MI-SED组（P<0.05）。HE染色显示，MI-HIIT组训练8周大鼠的心脏组织炎性病变较训练4周大鼠减轻，心肌细胞排列更紧密。Masson染色结果显示训练8周后MI-HIIT组、MI-MICT组心肌组织胶原纤维占比低于MI-SED组。免疫组化结果显示训练4、8周后MI-HIIT组、MI-MICT组心肌组织血管新生数高于Sham组、MI-SED组，训练8周后MI-HIIT组心肌组织血管新生数高于MI-MICT组。训练4周后，MI-HIIT组血清TNF-α高于MI-SED组；训练8周后，MI-HIIT组血清TNF-α水平高于MI-MICT组。

AMI早期进行HIIT，可提高HMI、诱导心肌组织早期炎性反应、减轻心肌纤维化、促进血管新生，改善心室重构，总体效果优于MICT。