Abstract
Background and objective Moderate exercise is important for health; however, there are variations among individuals in terms of characterizing moderate intensity and it is difficult to identify. In light of this, the purpose of this study was to identify new objective indicators to determine effective exercise intensity. Methods This study involved both human and animal experiments. After subjecting mice to exercise of effective intensity, microarray analysis of circulating microRNA expression was conducted to identify candidates for objective indicators to determine effective exercise intensity. Then, we assessed if these microRNAs were altered after aerobic or resistance exercises in humans using quantitative real-time PCR. Twelve healthy males were randomly assigned to two groups: the low-intensity exercise group (LI group) and the high-intensity exercise group (HI group) and they underwent four weeks of exercise program. Results Based on microarray analysis, 188 microRNAs were altered after aerobic exercise, and 167 microRNAs were altered after resistance exercise. Combining these findings with the data from some published reports, we selected miR-29c, miR-23b, miR-222, miR-195, miR-126, miR-133a, and miR-486 as the candidates for biomarkers to determine the effective exercise intensity. In the human study, physical performance improved after resistance exercise only in the HI group. Of the microRNAs, miR-29c, miR-195, and miR-486 increased immediately after resistance exercise only in the HI group. Fold change of miR-486 correlated with changes in knee extensor strength (r=0.744, p=0.005). Conclusions Resistance exercise at effective intensity upregulated the expression of miR-29c, miR-195, and miR-486. Hence, these microRNAs may serve as objective indicators to determine the intensity of resistance exercise. Among them, miR-486 may aid in predicting the response to resistance exercise.