title: New insights on contraction efficiency in patients with Duchenne muscular dystrophy.
abstract: The decrease in muscle strength in patients with Duchenne muscular dystrophy (DMD) is mainly explained by a decrease in the number of active contractile elements. Nevertheless, it is possible that other electrochemical and force transmission processes may contribute. The present study aimed to quantify the effect of DMD on the relative contribution of electrochemical and force transmission components of the electromechanical delay (i.e., time lag between the onset of muscle activation and force production) in humans using very high frame rate ultrasound. Fourteen patients with DMD and thirteen control subjects underwent two electrically evoked contractions of the biceps brachii with the ultrasound probe over the muscle belly. The electromechanical delay was significantly longer in DMD patients compared with controls (18.5 ± 3.9 vs. 12.5 ± 1.4 ms, P < 0.0001). More precisely, DMD patients exhibited a longer delay between the onset of muscle fascicles motion and force production (13.6 ± 3.1 vs. 7.9 ± 2.0 ms, P < 0.0001). This delay was correlated to the chronological age of the DMD patients (r = 0.66; P = 0.01), but not of the controls (r = -0.45; P = 0.10). No significant difference was found for the delay between the onset of muscle stimulation and the onset of muscle fascicle motion. These results highlight the role of the alteration of muscle force transmission (delay between the onset of fascicle motion and force production) in the impairments of the contraction efficiency in patients with DMD.
authors.affiliation: Laboratory Motricité, Interactions, Performance (EA 4334), Unite de Formation et de Recherche Sciences et Techniques des Activités Physiques et Sportives, University of Nantes, Nantes, France;
authors.forename: Lilian
authors.initials: L
authors.lastname: Lacourpaille
authors.affiliation: Laboratory Motricité, Interactions, Performance (EA 4334), Unite de Formation et de Recherche Sciences et Techniques des Activités Physiques et Sportives, University of Nantes, Nantes, France; National Health and Medical Research Council, Centre of Clinical Research Excellence in Spinal Pain, Injury and Health, School of Health and Rehabilitation Sciences, University of Queensland, Brisbane, Queensland, Australia; francois.hug@univ-nantes.fr.
authors.forename: François
authors.initials: F
authors.lastname: Hug
authors.affiliation: Laboratory Motricité, Interactions, Performance (EA 4334), Unite de Formation et de Recherche Sciences et Techniques des Activités Physiques et Sportives, University of Nantes, Nantes, France;
authors.forename: Arnaud
authors.initials: A
authors.lastname: Guével
authors.affiliation: Centre de Référence Maladies Neuromusculaires Nantes-Angers, University of Nantes, Centre Hospitalier Universitaire, Nantes, France; Atlantic Gene Therapies, Nantes, France; and.
authors.forename: Yann
authors.initials: Y
authors.lastname: Péréon
authors.affiliation: Centre de Référence Maladies Neuromusculaires Nantes-Angers, University of Nantes, Centre Hospitalier Universitaire, Nantes, France; Atlantic Gene Therapies, Nantes, France; and.
authors.forename: Armelle
authors.initials: A
authors.lastname: Magot
authors.affiliation: Institut de Myologie, GH Pitié-Salpêtrière, Paris, France.
authors.forename: Jean-Yves
authors.initials: JY
authors.lastname: Hogrel
authors.affiliation: Laboratory Motricité, Interactions, Performance (EA 4334), Unite de Formation et de Recherche Sciences et Techniques des Activités Physiques et Sportives, University of Nantes, Nantes, France;
authors.forename: Antoine
authors.initials: A
authors.lastname: Nordez
mesh_terms: D000293:Adolescent; D001132:Arm / Q000503:physiopathology; D002648:Child; D002675:Child, Preschool; D054459:Elasticity Imaging Techniques; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D009119:Muscle Contraction; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000503:physiopathology*; D020388:Muscular Dystrophy, Duchenne / Q000000981:diagnostic imaging / Q000503:physiopathology*; D009435:Synaptic Transmission; D055815:Young Adult
keywords: electromechanical delay; force; myopathy; ultrasound
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