title: Impaired regulation post-stroke of motor unit firing behavior during volitional relaxation of knee extensor torque assessed using high density surface EMG decomposition.
abstract: The purpose of this study was to use high density surface EMG recordings to quantify stroke-related abnormalities in motor unit firing behavior during repeated sub-maximal knee extensor contractions. A high density surface EMG system (sEMG) was used to record and extract single motor unit firing behavior in the vastus lateralis muscle of 6 individuals with chronic stroke and 8 controls during repeated sub-maximal isometric knee extension contractions. Paretic motor unit firing rates were increased with subsequent contractions (6.19±0.35 pps vs 7.89±0.66 pps, P <; 0.05) during task phases of torque decline as compared to controls (6.95±0.40 pps vs 6.68±0.41 pps). In addition, corresponding rates of torque decline were decreased for the paretic leg as compared to the non-paretic leg. These results suggest that regulation of declining forces may be impaired post stroke due to prolonged firing of paretic motor units.
authors.forename: Spencer A
authors.initials: SA
authors.lastname: Murphy
authors.forename: Reivian
authors.initials: R
authors.lastname: Berrios
authors.forename: P Andrew
authors.initials: PA
authors.lastname: Nelson
authors.forename: Francesco
authors.initials: F
authors.lastname: Negro
authors.forename: Dario
authors.initials: D
authors.lastname: Farina
authors.forename: Brian
authors.initials: B
authors.lastname: Schmit
authors.forename: Allison
authors.initials: A
authors.lastname: Hyngstrom
mesh_terms: D004576:Electromyography; D006801:Humans; D007537:Isometric Contraction; D007717:Knee; D018482:Muscle, Skeletal; D020521:Stroke; D019415:Torque