Quantitative MRI Evaluation of the Effects of Rest and Different Intensities of Running on the Recovery of Thigh Muscle Microdamage After a Half Marathon

Objective To explore the application value of quantitative magnetic resonance multi-parameter imaging technology, namely Diffusion Tensor Imaging (DTI) combined with T2 mapping, in evaluating the effects of rest and different intensities of running on the recovery of thigh muscle microdamage after a Half Marathon (HM). Methods Twenty-four amateur marathon runners were enrolled and divided into three groups: the High-Intensity Running (HIR) group, the Moderate-Intensity Running (MIR) group, and the Rest (REST) group. MR scans were performed on the participants before the race (pre-run) and at 3 hours (post-3h), 24 hours (post-24h), 48 hours (post-48h), and 72 hours (post-72h) after the race. The Fractional Anisotropy (FA), Apparent Diffusion Coefficient (ADC), and T2 relaxation time (T2 value) of the thigh muscle groups were measured. Results At post-3h, the FA values in all three groups decreased significantly (P<0.001) and the T2 values increased significantly (P<0.001), indicating that HM induced muscle microdamage. In the REST group, the FA values began to recover at post-24h and returned to the pre-run level at post-72h. In the MIR group, the FA values started to recover at post-48h but did not fully recover by post-72h. In the HIR group, there was no significant recovery of FA values throughout the observation period (P>0.99). The change trend of T2 values was consistent with that of FA values. Conclusion Quantitative MR multi-parameter imaging can sensitively detect muscle microdamage and the recovery process after HM. The REST group showed the fastest recovery, while moderate- and high-intensity running delayed recovery. Therefore, it is not recommended to use running as an intervention within 3 days after the race.