Heart Rate Variability During Moderate-intensity Continuous Running Associations With Elevated Circulating Muscle-specific MicroRNAs

Acute prolonged endurance running has been shown to alter muscle-specific circulating microRNAs(miRNAs)levels.Here we examined the acute changes of four circulating miRNAs(miR-1,miR-133a,miR-133b and miR-206),internal load and conventional cardiac damage makers after short-duration exercise,and whether there is a correlation between the changes of miRNAs and the other two factors.Ten participants completed an 8 km running exercise.Internal load was analyzed using Firstbeat SPORTS.Circulating miRNAs in plasma were detected using TaqMan-based quantitative PCR and normalized to miR-2911 and cardiac damage markers were measured.Acute exercise significantly increased candidate plasma levels of miR-1,miR-133a,miR-133b and miR-206(p<0.001).Cardiac troponin I levels were below the detection limit of the assay(<0.05 ng·ml-1)for all participants before and immediately post-exercise,and no significant difference was found in creatine kinase MB isoenzyme,while acute exercise signficantly increased levels of myoglobin(Myo)(p<0.001).Alterations in circulating miR-133a and miR-206 were moderately to strongly correlated with changes in root of the mean squared successive differences of in RR intervals(RMSSD).No correlations were found between the four muscle-specific miRNAs and other parameters of the training internal load.In addition,the fold changes of miR-133a and miR-133b also moderately to strongly correlated with Myo.These findings suggest that muscle-specific miRNAs elevation in plasma is likely physiological and benign in the context of endurance exercise.Moreover,correlation between miR-133a,miR-133b and miR-206 levels with RMSSD and Myo suggests that these miRNAs can be used as potential biomarkers of individual load monitoring.