Background The 12-lead electrocardiogram (ECG) has been adopted as an important component of preparticipation cardiovascular screening. However, there are still controversies in the screening and few studies with a large sample size have reported the results of ECGs of marathon runners. Therefore, the purpose of this study was to assess the prevalence of normal, borderline, and abnormal ECG changes in marathon runners. Methods The 12-lead ECG data of 13,079 amateur marathon runners between the ages of 18 and 35 years were included for analysis. The prevalence of ECG abnormalities among different gender groups was compared with chi-square tests. Results In terms of training-related changes, sinus bradycardia, sinus arrhythmia, and left ventricular high voltage were found in approximately 15, 5, and 3.28% of the participants, respectively. The incidence of right axis deviation in the marathon runners was 1.78%, which was slightly higher than the incidence of left axis deviation (0.88%). No more than 0.1% of the amateur marathon runners exhibited ST-segment depression, T wave inversion (TWI), premature ventricular contraction, pathologic Q waves, and prolonged QT interval. Conclusions Training-related ECG changes, including sinus bradycardia, sinus arrhythmia, and left ventricular high voltage, were common in amateur marathon runners. Most abnormal ECG changes, including ST-segment depression, TWI, premature ventricular contraction, pathologic Q waves, and prolonged QT interval, were infrequently found in amateur marathon runners. The data also suggested Chinese amateur marathon runners may have a relatively lower prevalence of ECG abnormalities than black and white runners.

Background Velocity lactate threshold (VLT) is commonly used as a standard for exercise intensity, although previous studies of VLT have focused mostly on well-trained athletes. Heart rate (HR) is an important physiological index which is easy to measure, the heart rate-workload relationship curve is the reported coincidence with lactate threshold (LT). This study aimed to develop valid, simple and economical velocity at lactate threshold prediction methods for general Chinese adults. Methods Eighty-four Chinese adults (49 males and 35 females aged 27.1 ± 8.3 years) were recruited to perform a graded exercise test on a treadmill. A 20-s rest time for the blood sample collection was set between each 3-min successive stage. Blood lactate concentration and heart rate (HR) were determined using a blood lactate analyser and HR monitors. Multiple linear regressions were applied to develop VLT prediction models using velocity at different HR levels, genders, BMI and ages as dependent variables. Results Eight VLT prediction models were established, in which 47%–65% of variance of VLT could be explained. The results of the paired t-tests showed no significant difference can be observed between estimated and measured VLTs. Conclusion In conclusion, simple and convenient VLT prediction models were established, and the models are valid in predicting VLT for general population.

The purpose of this study was to assess the prevalence of normal, borderline and abnormal ECG changes in marathon runners. The 12-lead ECG data of 13,079 amateur marathon runners between the ages of 18 and 35 years were included for analysis. The prevalence of ECG abnormalities among different gender groups was compared with chi-square tests. In terms of training-related changes, sinus bradycardia, sinus arrhythmia and left ventricular high voltage were found in approximately 15%, 5% and 3.28% of the participants, respectively. The incidence of right axis deviation in the marathon runners was 1.78%, which was slightly higher than the incidence of left axis deviation (0.88%). No more than 0.1% of the amateur marathon runners exhibited ST segment depression, T wave inversion (TWI), premature ventricular contraction, pathologic Q waves and prolonged QT interval. In conclusion, training-related ECG changes, including sinus bradycardia, sinus arrhythmia and left ventricular high voltage, were common in the amateur marathon runners. Most of abnormal ECG changes, including ST segment depression, TWI, premature ventricular contraction, pathologic Q waves and prolonged QT interval, were infrequently found in the amateur marathon runners.