title: Heterogeneity of muscle damage induced by electrostimulation: a multimodal MRI study.
abstract: OBJECTIVE
  Neuromuscular electrostimulation (NMES) leads to a spatially fixed, synchronous, and superficial motor unit recruitment, which could induce muscle damage. Therefore, the extent of muscle damage and its spatial occurrence were expected to be heterogeneous across and along the quadriceps femoris (QF) muscles. The aim of the present study was to characterize muscle spatial heterogeneity in QF damage after a single bout of isometric NMES using multimodal magnetic resonance imaging (MRI).
  
  
  METHODS
  Twenty-five young healthy males participated in this study. MRI investigations consisted of the assessment of muscle volume, transverse relaxation time (T2), and diffusion tensor imaging (DTI) in muscles positioned near the stimulation electrodes (i.e., vastus lateralis (VL) and vastus medialis (VM)) and muscles located outside the stimulated regions (i.e., vastus intermedius and rectus femoris). These measurements were performed 6 d before, and 2 d and 4 d (D4) after the NMES session.
  
  
  RESULTS
  For the muscles placed in direct contact with the stimulation electrodes, volume (VL, +8.5%; VM, +3.8%), T2 (VL, +19.5%; VM, +6.7%) and radial diffusivity (λ3) (VL, + 7.3%; VM, +3.7%) significantly increased at D4. Whereas MRI parameter changes were larger for VL as compared with those for other QF muscles at D4, homogeneous alterations were found along all QF muscles.
  
  
  CONCLUSIONS
  Isometric NMES induced specific and localized alterations in VL and VM, with heterogeneous damage amplitude among them. Potential effects of unaccustomed intermuscle shear stress during electrically evoked isometric contractions could be a key factor in the spatial occurrence and the extent of damage among QF muscles (especially in VL). The kinetics and extent of MRI changes varied between T2 and diffusion tensor imaging metrics, suggesting the involvement of different physiological processes.
authors.affiliation: 1Aix-Marseille University, Centre National de la Recherche Scientifique (CNRS), Centre de Résonance Magnétique Biologique et Médicale (CRMBM), Unité Mixte de Recherche 7339, Marseille, FRANCE; 2Assistance Publique des Hôpitaux de Marseille (APHM), La Timone Hospital, Imaging Center, Centre d'Exploration Métabolique par Résonance Magnétique (CEMEREM), Marseille, FRANCE; and 3APHM, Sainte Marguerite Hospital, Department of Rheumatology, Marseille, FRANCE.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Fouré
authors.forename: Guillaume
authors.initials: G
authors.lastname: Duhamel
authors.forename: Jennifer
authors.initials: J
authors.lastname: Wegrzyk
authors.forename: Hélène
authors.initials: H
authors.lastname: Boudinet
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Mattei
authors.forename: Arnaud
authors.initials: A
authors.lastname: Le Troter
authors.forename: David
authors.initials: D
authors.lastname: Bendahan
authors.forename: Julien
authors.initials: J
authors.lastname: Gondin
mesh_terms: D003402:Creatine Kinase / Q000097:blood; D056324:Diffusion Tensor Imaging; D004558:Electric Stimulation / Q000009:adverse effects*; D006801:Humans; D007537:Isometric Contraction; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009126:Muscle Relaxation; D063806:Myalgia / Q000209:etiology; D009929:Organ Size; D052097:Quadriceps Muscle / Q000473:pathology* / Q000503:physiopathology; D013997:Time Factors; D055815:Young Adult
chemical_list: D003402:Creatine Kinase