Electromechanical delay components during skeletal muscle contraction and relaxation in patients with myotonic dystrophy type 1

Abstract

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights Patients with myotonic dystrophy type 1 (DM1) were investigated isometrically  We calculated the electromechanical delays during muscle contraction and relaxation  Delays were partitioned into electrochemical and mechanical components  Measurements reliability was very high in both patients and controls  Delays were longer in DM1, especially during muscle relaxation AbstractThe electromechanical delay during muscle contraction and relaxation can be partitioned into mainly electrochemical and mainly mechanical components by an EMG, mechanomyographic, and force combined approach. Components duration and measurements reliability were investigated during contraction and relaxation in a group of patients with myotonic dystrophy type 1 (DM1, n=13) and in healthy controls (n=13). EMG, mechanomyogram, and force were recorded in DM1 and in age-and body-matched controls from tibialis anterior (distal muscle) and vastus lateralis (proximal muscle) muscles during maximum voluntary and electrically-evoked isometric contractions. The electrochemical and mechanical components of the electromechanical delay during muscle contraction and relaxation were calculated off-line. Maximum strength was significantly lower in DM1 than in controls under both experimental conditions. All electrochemical and mechanical components were significantly longer in DM1 in both muscles.Measurements reliability was very high in both DM1 and controls. The high reliability of the measurements and the differences between DM1 patients and controls suggest that the EMG, mechanomyographic, and force combined approach could be utilized as a valid tool to assess the level of neuromuscular dysfunction in this pathology, and to follow the efficacy of pharmacological or non-pharmacological interventions.

Reaction time can be measured during voluntary contractions with electrode array

“…In the present study, we found acceptable CV and poor-tohigh ICC (Atkinson & Nevill, 1998). Although lower CV and higher ICC for EMD were previously observed during voluntary contractions (Hopkins et al, 2007;Esposito et al, 2016), studies that have assessed EMD during a simple RT task are scarce, more or less recent (Krall, 1973;Klimovitch, 1977;Stull & Kearney, 1978) and/or did not use electrode array (P€ a€ asuke et al, 1999). It has been proposed that, for longer RT measured in various tasks, the delayed onset of physical processes regulated by white and grey matter initiated later in time, thus explaining the RT variability (Yarkoni et al, 2009).…”

Crouch gait can be an effective form of forced-use/no constraint exercise for the paretic lower limb in stroke

“…Yet, the time of electric activity anticipates the time of detectable force because of the time needed for impulse conduction, excitation–contraction coupling, alignment of pennate fibers with the tendon, and stiffening of the series elastic elements ( Nordez et al , 2009 ), so that the overall electromechanical delay for force onset was presumably around 50–80 ms in this study. The delay is known to be higher for contraction than for relaxation ( Esposito et al , 2016 ). Also, as a rule, the sEMG signal decreased monotonically from just before to just after the time of detectable positive power (Figs 2 – 4 ), so that the missed sEMG was of non-negligible amplitude.…”

Oropharyngeal dysphagia in early stages of myotonic dystrophy type 1

“…Thirty‐three unrelated participants with no myotonia, muscle weakness, or clinical history of DM1 were included in the study as presymptomatic candidates. In addition to being DM1 mutation carriers, presymptomatic participants met the following criteria: (1) absence of distal weakness measured according to the Muscular Impairment Rating Scale and by hand‐held dynamometry using reference values adjusted for age and sex (28.46 ± 7.17 and 23.95 ± 6.26 for right and left hands, respectively) and (2) lack of myotonic discharges according to needle examination of cervical paraspinal, trapezius, deltoid, biceps, wrist extensor, first dorsal interosseous, tibialis anterior, and vastus lateralis muscles (Nicolet Viasys Viking Select, Madison, Wisconsin) . Participants with another neuromuscular or neurodegenerative disease, stroke, traumatic brain injury, head and neck cancer, or dystonia were excluded.…”