MR elastography measurement of the effect of passive warmup prior to eccentric exercise on thigh muscle mechanical properties

Citation

Kennedy P, Macgregor LJ, Barnhill E, Johnson C, Perrins M, Hunter A, Brown C, van Beek EJR & Roberts N (2017) MR elastography measurement of the effect of passive warmup prior to eccentric exercise on thigh muscle mechanical properties. Journal of Magnetic Resonance Imaging, 46 (4), pp. 1115-1127. https://doi.org/10.1002/jmri.25642

Abstract
Purpose: To investigate the effect of warmup by application of the thermal agent Deep Heat (DH) on muscle mechanical properties using magnetic resonance elastography (MRE) at 3T before and after exercise-induced muscle damage (EIMD).  Materials and Methods: Twenty male participants performed an individualized protocol designed to induce EIMD in the quadriceps. DH was applied to the thigh in 50% of the participants before exercise. MRE, T2-weighted MRI, maximal voluntary contraction (MVC), creatine kinase (CK) concentration, and muscle soreness were measured before and after the protocol to assess EIMD effects. Five participants were excluded: four having not experienced EIMD and one due to incidental findings.  Results: Total workload performed during the EIMD protocol was greater in the DH group than the control group (P < 0.03), despite no significant differences in baseline MVC (P=0.23). Shear stiffness |G*| increased in the rectus femoris (RF) muscle in both groups (P < 0.03); however, DH was not a significant between-group factor (P= 0.15). MVC values returned to baseline faster in the DH group (5 days) than the control group (7 days). Participants who displayed hyperintensity on T2-weighted images had a greater stiffness increase following damage than those without: RF; 0.61 kPa vs. 0.15 kPa, P < 0.006, vastus intermedius; 0.34 kPa vs. 0.03 kPa, P =0.06.  Conclusion: EIMD produces increased muscle stiffness as measured by MRE, with the change in |G*| significantly increased when T2 hyperintensity was present. DH did not affect CK concentration or soreness; however, DH participants produced greater workload during the EIMD protocol and exhibited accelerated MVC recovery.  Level of Evidence: 1. 

Keywords
exercise induced muscle damage; MR elastography; thigh

Journal
Journal of Magnetic Resonance Imaging: Volume 46, Issue 4

People

Professor Angus Hunter

Honorary Professor, FHSS Management and Support

Dr Lewis Macgregor

Lecturer in Physiology and Nutrition, Sport