CHANGES IN MUSCLE T2 AND TISSUE DAMAGE AFTER DOWNHILL RUNNING IN mdx MICE

Introduction: In this study we compared the effects of downhill or horizontal treadmill running on the magnetic resonance imaging (MRI) transverse relaxation time constant (T-2) in mdx mice. Methods: Mice underwent either downhill (n = 11 mdx, n = 6 controls) or horizontal running (n = 9, mdx only) on a treadmill. MRI was conducted prior to exercise, immediately afterward (similar to 20 minutes), and then 24 and 48 hours after exercise. Results: A higher percentage of pixels with elevated T-2 in the lower hindlimb muscles was observed in the mdx mice compared with controls both pre-exercise (P < 0.001) and at each time-point after downhill running (P < 0.05), but not with horizontal running. The medial compartment muscles appeared to be the most susceptible to increased T-2. Conclusions: Downhill running provides a stimulus for inducing acute changes in muscle T-2 in mdx mice. MRI is a non-invasive approach for examining acute muscle damage and recovery in multiple muscle groups simultaneously. Muscle Nerve 43: 878-886, 2011