[Analysis of the characteristics of MRI T value changes of the muscles around the knee joint before and after the race in amateur marathon runners based on T mapping].

To evaluate the characteristics of MRI T value changes of muscles around the knee joint in amateur marathon athletes based on T mapping. A total of 12 amateur marathon runners (5 males and 7 females) were recruited as the marathon group, aged from 21 to 37(27.5±5.4) years. MRI examination of bilateral knee joint was performed one week before the race, within 12 hours after the race and two months after the race, respectively. Fifteen healthy volunteers (5 males and 10 females) were recruited as the control group, aged from 24 to 27(24.9±1.0) years, and underwent MRI examination of both knee joints. The T mapping imaging sequence was used to measure the T values of the sartorius, vastus medialis, biceps femoris, semimembranosus, medial head of gastrocnemius and lateral gastrocnemius head on the post-processing platform, and analyzed the marathon group before and after the race. The differences in the T value of each muscle of the marathon group before and after the race within 12 hours, before and 2 months after the race, and between the control group and the marathon group before the marathon were analyzed. All subjects had not knee joint pain during the examination. Routine MRI examination showed that there was no obvious abnormality in the shape and signal of the muscles around the knee joint. The T value of the semimembranosus [(34.3±2.8) ms vs (35.5±2.5) ms, =0.008], medial head of gastrocnemius [(34.1±3.4) ms vs (37.7±3.1) ms,<0.001] and lateral head of gastrocnemius [(35.2±2.9) ms vs (37.2±3.9) ms,=0.011] increased after the competition compared with that of pre-competition in the marathon group, while the T value of the remaining muscles showed no significant difference compared with that of pre-competition(>0.05). At the follow-up of 2 months, the T value of semimembranosus remains higher than before the marathon [(34.3±2.8) ms vs (35.4±2.5) ms,=0.043], and the T value of the medial head of the gastrocnemius and lateral head of gastrocnemius showed no statistically difference compared with pre-competition (>0.05). Compared with the control group, the T value of the lateral head of the gastrocnemius in the marathon group was decreased [(35.3±3.0) ms vs (38.5±4.1) ms,=0.007]. There was no significant difference in the T value of the remaining muscles in the marathon group (>0.05). After the marathon, the changes in the T value of the muscles around the knee joint is reversible. T mapping imaging sequence can indirectly reflect the changes of skeletal muscle microstructure to a certain extent.