Study Population
72 participants were recruited.After excluding invalid information(( hypertension (n = 2), arrhythmia (n = 1)), no heart-related diseases were found in rest of the volunteers during routine physical examinations before entering a group). 69 healthy volunteers were assessed. And all participants were divided into two groups( the exercise group and the control group).According to the criterias, the exercise group self-reported on the fulfillment of prespecified exercise criteria, as listed in the appendix(Table 1). The control group received daily basic life and exercise standards (using the exercise software, 5000–8000 steps/day only, and no weekly long-distance running, ball games, horizontal bar training, skipping rope, push-up, and sit-up training lasting for at least 4 years .All the recruited participants received CMR imaging. At last, the study included 67 healthy volunteers (the exercise group(n = 43) and the control group(n = 23)) as showed in the flowchart (Fig. 1).
Table 1
The exercise group received aerobic exercise of a certain intensity for 3-5times per week lasting for 4 years,Choose one of the sports standards between ball games and 3-5km long distance running. And the rest of the sports should be simultaneously satisfied by the gender
Exercise Criteria |
Male | Female |
horizontal bar training (30–50 times per day) | sit-ups ( 50 times per day) |
push-ups ( 50 times per day) | rope skipping ( 100–300 times per day) |
Data collection
The MRI scan was performed on all the subjects using a 3T MRI scanner (MAGNETOM Trio a Tim system, Siemens Healthcare, Erlangen, Germany) with a 6-channel body matrix coil plus 2 rows of the spine array coils, used to improve field uniformity with a target cardiac shimming mode. We compared the differences in the cardiac function parameters and myocardial strain values between the controls and exercise group. We acquired nonenhanced cardiac cine images with 25 reconstructed phases using balanced steady-state free-precession (bSSFP) sequence with retrospective electrocardiogram (ECG) gating. The collected subject information included the data from cardiac short axes, 2-chamber view, and 4-chamber view. The scan parameters were as the following: slice thickness = 6 mm, time of echo = 1.7 ms, field of view (FOV) = 325 x 400 mm², matrix = 256 x 256, and slice thickness = 1.5 mm. The commercial software, cvi42 (Circle Cardiovascular Imaging Inc., Calgary, Alberta, Canada), was used for post-processing using the 3D short module and 3D tissue tracking module. Endo- and epicardial contours were manually traced to measure the LV cavity at end-diastole and end-systole. The inner membrane contour was distanced from the blood pool, and the outer membrane contour was distanced from the fat outside of the heart and right ventricular blood pool to avoid the partial volume effects. The papillary muscles were included in the LV volume. The LV end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), ejection fraction (EF), cardiac index (CI), myocardial mass index (Myo Mass ), global radial strain (GRS), global circumferential strain (GCS), and global longitudinal strain (GLS) parameters were obtained.
Statistical Analyses
The SPSS software version 19.0 (IBM Corp., Armonk/NY, USA) was used for data analysis. We compared the differences in each value using independent sample t tests. P-values < 0.05 were considered statistically significant. The data were expressed as the means ± the standard deviations. Mean differences between the groups were compared using paired t-tests and the Bland-Altman methods. The Pearson’s method was used to analyze the relationships between the myocardial strain and cardiac function. The person that analyzed the MRIs was blinded to the study groups. For inter-observer reproducibility, two radiologists (each with > 10 years of experience) independently analyzed the images from five randomly selected participants. Furthermore, one radiologist (with > 5 years of experience) reanalyzed the images of ten participants after one month. The sample sizes were also calculated. Statistical tests were two-tailed, and the statistical significance was defined as a p-value < 0.05. Strain measurements were very reproducible between the different examiners. Statistical analyses were performed using SPSS (version 21.0, SPSS, Inc., Chicago, IL, USA), GraphPad Prism (version 6.01, GraphPad Software, Inc., La Jolla, CA, USA), and MedCalc (version 11.4.2.0, MedCalc Software, Ostend, Belgium) software.