[Diffusion tensor imaging in quantitative evaluation on thigh muscle of male amateur marathon runners after running a half marathon].

To investigate the effect of half marathon on thigh muscle in male amateur marathon runners by diffusion tensor imaging (DTI). A total of 17 male amateur marathon runners aged from 27 to 57 (43.7±2.8) years were recruited from May to August 2020 in Hangzhou, Zhejiang Province. MRI examination of bilateral thigh muscles were performed before and 3 h, 3 d and 7 d after a half marathon. The fractional anisotropy (FA) values was obtained by DTI sequence. The FA values of rectus femoris, intermedius femoris, medial femoris, lateral femoris, biceps femoris longus, semitendinosus, semimembranosus, adductor magnus and adductor longus were measured on the horizontal axis of bilateral thigh muscles. Friedman test was used to compare the changes of FA values of each muscle at each time point before and after running, and pairwise comparison of FA values of statistically significant muscles at 3 h, 3 d and 7 d after running was performed. The overall FA value of thigh muscle group [ (, )] at 3 h after running was decreased compared to before running [0.24 (0.20, 0.28) to 0.25 (0.21, 0.29), <0.001], and there was no significant difference between baseline values at 3 d and 7 d after running (all >0.05). FA values of vastus intermedius, vastus medialis, semimembranosus and adductor magnus at 3 h after running were lower than those before running [(0.19 (0.18, 0.22) vs 0.21 (0.19, 0.24), 0.19 (0.17, 0.20) vs 0.21 (0.18, 0.23), 0.26 (0.24), 0.29) vs 0.27 (0.15, 0.30) and 0.20 (0.19, 0.22) vs 0.21 (0.20, 0.23), both 0.05], and there was no statistical significance between 3 d and 7 d after running and those before running (all >0.05). FA value of vastus lateralis muscle at 3 h after running decreased compared with that before running, but the difference was not statistically significant (0.05). FA value began to increase at 7 d after running, and the difference was statistically significant [0.24 (0.21, 0.27) vs 0.23 (0.19, 0.25), = 0.002]. FA value of rectus femoris muscle at 3 h after running decreased compared with that before running, but the difference was not statistically significant (>0.05), and began to increase at 3 d after running and the difference was statistically significant [0.29 (0.26, 0.34) vs 0.26 (0.23, 0.29), =0.006]. FA value of adductor longus muscle increased at 3 h after running, but the difference was not statistically significant (>0.05). FA value continued to increase at 3 d and 7 d after running, and the difference was statistically significant [0.23 (0.21, 0.25) vs 0.22 (0.19, 0.24), 0.23 (0.21, 0.26) vs 0.22 (0.19, 0.24), all <0.05]. The change of FA value of thigh muscle after half marathon is reversible. At 3 h after half marathon, FA values of femoris intermedius, femoris medialis, semimembranosus muscle and adductor magnus muscle of amateur marathon runners decreased most obviously, which may be the dominant muscle group during running.