Dynamic DTI (dDTI) shows differing temporal activation patterns in post-exercise skeletal muscles
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To assess post-exercise recovery of human calf muscles using dynamic diffusion tensor imaging (dDTI).
Materials and methods
DTI data (6 directions, b = 0 and 400 s/mm2) were acquired every 35 s from seven healthy men using a 3T MRI, prior to (4 volumes) and immediately following exercise (13 volumes, ~7.5 min). Exercise consisted of 5-min in-bore repetitive dorsiflexion-eversion foot motion with 0.78 kg resistance. Diffusion tensors calculated at each time point produced maps of mean diffusivity (MD), fractional anisotropy (FA), radial diffusivity (RD), and signal at b = 0 s/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.
KeywordsDTI Skeletal muscle Exercise Recovery Time course Human
Funding was provided to CR in the form of a Natural Sciences and Engineering Research Council (NSERC) of Canada CGS-D PhD scholarship. The research was funded through an NSERC Discovery grant to MDN.
Compliance with ethical standards
Conflict of interest
No author has any potential conflict of interest with respect to the work described and performed in this current manuscript. Dr. Michael Noseworthy has received a one-time lecture honorarium from GE Healthcare (Canada) for two 50-min lectures delivered in September 2015 to MRI technologists. These lectures were not in any way related to the current work.
Research involving human participants and/or animals
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
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