title: MR elastography measurement of the effect of passive warmup prior to eccentric exercise on thigh muscle mechanical properties.
abstract: 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).
  
  
  
  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.
  
  
  
  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.
  
  
  
  EIMD produces increased muscle stiffness as measured by MRE, with the change in |G*| significantly increased when T2hyperintensity 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.
  
  
  
  1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2017;46:1115-1127.
authors.affiliation: Clinical Research Imaging Centre (CRIC), Queen's Medical Research Institute, University of Edinburgh, Edinburgh, UK.|Translational and Molecular Imaging Institute (TMII), Icahn School of Medicine at Mount Sinai, New York, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Kennedy
authors.affiliation: Health and Exercise Research Group, School of Sport, University of Stirling, UK.
authors.forename: Lewis J
authors.initials: LJ
authors.lastname: Macgregor
authors.affiliation: Department of Radiological Science, Charité-Universitätsmedizin, Berlin, Germany.
authors.forename: Eric
authors.initials: E
authors.lastname: Barnhill
authors.affiliation: Department of Biomedical Engineering, University of Delaware, Newark, Delaware, USA.
authors.forename: Curtis L
authors.initials: CL
authors.lastname: Johnson
authors.affiliation: Clinical Research Imaging Centre (CRIC), Queen's Medical Research Institute, University of Edinburgh, Edinburgh, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Perrins
authors.affiliation: Health and Exercise Research Group, School of Sport, University of Stirling, UK.
authors.forename: Angus
authors.initials: A
authors.lastname: Hunter
authors.affiliation: The Mentholatum Company Ltd, East Kilbride, Glasgow, UK.
authors.forename: Colin
authors.initials: C
authors.lastname: Brown
authors.affiliation: Clinical Research Imaging Centre (CRIC), Queen's Medical Research Institute, University of Edinburgh, Edinburgh, UK.
authors.forename: Edwin J R
authors.initials: EJR
authors.lastname: van Beek
authors.affiliation: Clinical Research Imaging Centre (CRIC), Queen's Medical Research Institute, University of Edinburgh, Edinburgh, UK.
authors.forename: Neil
authors.initials: N
authors.lastname: Roberts
mesh_terms: D000328:Adult; D054459:Elasticity Imaging Techniques / Q000379:methods*; D015444:Exercise / Q000502:physiology*; D006358:Hot Temperature / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000503:physiopathology*; D010146:Pain / Q000503:physiopathology* / Q000517:prevention & control; D013848:Thigh / Q000000981:diagnostic imaging / Q000503:physiopathology; D055815:Young Adult
keywords: MR elastography; exercise induced muscle damage; thigh