title: Electromechanical delays during a fatiguing exercise and recovery in patients with myotonic dystrophy type 1.
abstract: OBJECTIVE
  The partitioning of the electromechanical delay by an electromyographic (EMG), mechanomyographic (MMG) and force combined approach can provide further insight into the electrochemical and mechanical processes involved with skeletal muscle contraction and relaxation. The aim of the study was to monitor by this combined approach the changes in delays' electrochemical and mechanical components throughout a fatiguing task and during recovery in patients with myotonic dystrophy type 1 (DM1), who present at the skeletal muscle level fibres rearrangement, muscle weakness and myotonia, especially in the distal muscles.
  
  
  METHODS
  After assessing maximum voluntary contraction (MVC), 14 male patients with DM1 and 14 healthy controls (HC) performed a fatiguing exercise at 50% MVC until exhaustion. EMG, MMG, and force signals were recorded from tibialis anterior and vastus lateralis muscles. The electromechanical delay during contraction (DelayTOT) and relaxation (R-DelayTOT) components, EMG and MMG root mean square (RMS) and mean frequency (MF) were calculated off-line.
  
  
  RESULTS
  The fatiguing exercise duration was similar in both groups. In patients with DM1, delays components were significantly longer compared to HC, especially in the distal muscle during relaxation. Delays components recovered quickly from the fatiguing exercise in HC than in patients with DM1 in both muscles.
  
  
  CONCLUSIONS
  The alterations in delays observed in DM1 during the fatiguing exercise may indicate that also the lengthening of the electrochemical and mechanical processes during contraction and relaxation could play a role in explaining exercise intolerance in this pathology.
authors.affiliation: Department of Biomedical Sciences for Health (SCIBIS), Università degli Studi di Milano, Via G. Colombo 71, 20133, Milan, Italy. fabio.esposito@unimi.it.|IRCCS Fondazione don Gnocchi, Centro di Medicina dello Sport, via Capecelatro 66, 20148, Milan, Italy. fabio.esposito@unimi.it.
authors.forename: Fabio
authors.identifier: http://orcid.org/0000-0002-4420-2611
authors.initials: F
authors.lastname: Esposito
authors.affiliation: Department of Biomedical Sciences for Health (SCIBIS), Università degli Studi di Milano, Via G. Colombo 71, 20133, Milan, Italy.
authors.forename: Emiliano
authors.initials: E
authors.lastname: Cè
authors.affiliation: Department of Biomedical Sciences for Health (SCIBIS), Università degli Studi di Milano, Via G. Colombo 71, 20133, Milan, Italy.
authors.forename: Susanna
authors.initials: S
authors.lastname: Rampichini
authors.affiliation: Department of Biomedical Sciences for Health (SCIBIS), Università degli Studi di Milano, Via G. Colombo 71, 20133, Milan, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Monti
authors.affiliation: Department of Biomedical Sciences for Health (SCIBIS), Università degli Studi di Milano, Via G. Colombo 71, 20133, Milan, Italy.
authors.forename: Eloisa
authors.initials: E
authors.lastname: Limonta
authors.affiliation: IRCCS Policlinico San Donato, Piazza Malan 2, 20097, San Donato Milanese (MI), Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Fossati
authors.affiliation: Department of Biomedical Sciences for Health (SCIBIS), Università degli Studi di Milano, Via G. Colombo 71, 20133, Milan, Italy.|IRCCS Policlinico San Donato, Piazza Malan 2, 20097, San Donato Milanese (MI), Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Meola
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D015444:Exercise; D017079:Exercise Tolerance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D018763:Muscle Fatigue; D018482:Muscle, Skeletal / Q000503:physiopathology; D009223:Myotonic Dystrophy / Q000503:physiopathology*; D011930:Reaction Time
keywords: Electromyogram; Exercise intolerance; Latency; Mechanomyogram; Myotonia; Voluntary contraction