Dynamic DTI (dDTI) shows differing temporal activation patterns in post-exercise skeletal muscles.

Abstract

To assess post-exercise recovery of human calf muscles using dynamic diffusion tensor imaging (dDTI). DTI data (6 directions, b=0 and 400s/mm2) were acquired every 35s from seven healthy men using a 3T MRI, prior to (4 volumes) and immediately following exercise (13 volumes,~7.5min). Exercise consisted of 5-min in-bore repetitive dorsiflexion-eversion foot motion with 0.78kg resistance. Diffusion tensors calculated at each time point produced maps of mean diffusivity (MD), fractional anisotropy (FA), radial diffusivity (RD), and signal at b=0s/mm2 (S0). Region-of-interest (ROI) analysis was performed on five calf muscles: tibialis anterior (ATIB), extensor digitorum longus (EDL) peroneus longus (PER), soleus (SOL), and lateral gastrocnemius (LG). Active muscles (ATIB, EDL, PER) showed significantly elevated initial MD post-exercise, while predicted inactive muscles (SOL, LG) did not (p<0.0001). The EDL showed a greater initial increase in MD (1.90×10-4mm2/s) than ATIB (1.03×10-4mm2/s) or PER (8.79×10-5 mm2/s) (p=7.40×10-4), and remained significantly elevated across more time points than ATIB or PER. Significant increases were observed in post-exercise EDL S0 relative to other muscles across the majority of time points (p<0.01 to p<0.001). dDTI can be used to differentiate exercise-induced changes between muscles. These differences are suggested to be related to differences in fiber composition.