title: Specific joint angle dependency of voluntary activation during eccentric knee extensions.
abstract: BACKGROUND
  This study compared voluntary activation during isometric, concentric, and eccentric maximal knee extensions at different joint angles.
  
  
  METHODS
  Fifteen participants performed isometric, concentric, and eccentric protocols (9 contractions each). For each protocol, the central activation ratio (CAR) was randomly measured at 50°, 75°, or 100° of knee joint angle (0° = full knee extension) using superimposed supramaximal paired nerve stimulations during contractions.
  
  
  RESULTS
  CAR increased between 50° and 100° during isometric (93.6 ± 3.1 vs. 98.5 ± 1.4%), concentric (92.4 ± 5.4 vs. 99.2 ± 1.2%), and eccentric (93.0 ± 3.5 vs. 96.6 ± 3.8%) contractions. CAR was lower during eccentric than both isometric and concentric contractions at 75° and 100°, but similar between contraction types at 50°.
  
  
  CONCLUSIONS
  The ability to activate muscle maximally is impaired during eccentric contractions compared with other contraction types at 75° and 100°, but not at 50°. Muscle Nerve 56: 750-758, 2017.
authors.affiliation: Laboratory "Movement, Interactions, Performance" (EA 4334), 25 bis Boulevard Guy Mollet, Faculty of Sport Sciences, University of Nantes, 44322, Nantes, France.
authors.forename: Valentin
authors.initials: V
authors.lastname: Doguet
authors.affiliation: Laboratory "Movement, Interactions, Performance" (EA 4334), 25 bis Boulevard Guy Mollet, Faculty of Sport Sciences, University of Nantes, 44322, Nantes, France.
authors.forename: Valentin
authors.initials: V
authors.lastname: Rivière
authors.affiliation: Laboratory "Movement, Interactions, Performance" (EA 4334), 25 bis Boulevard Guy Mollet, Faculty of Sport Sciences, University of Nantes, 44322, Nantes, France.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Guével
authors.affiliation: French National Institute of Sport (INSEP), Research Department, Laboratory Sport, Expertise and Performance (EA 7370), Paris, France.
authors.forename: Gaël
authors.initials: G
authors.lastname: Guilhem
authors.affiliation: Laboratory "Movement, Interactions, Performance" (EA 4334), 25 bis Boulevard Guy Mollet, Faculty of Sport Sciences, University of Nantes, 44322, Nantes, France.
authors.forename: Lucile
authors.initials: L
authors.lastname: Chauvet
authors.affiliation: Laboratory "Movement, Interactions, Performance" (EA 4334), 25 bis Boulevard Guy Mollet, Faculty of Sport Sciences, University of Nantes, 44322, Nantes, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Jubeau
mesh_terms: D000293:Adolescent; D000328:Adult; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D053581:Muscle Strength Dynamometer; D052097:Quadriceps Muscle / Q000502:physiology*; D011897:Random Allocation; D055815:Young Adult
keywords: central activation ratio; isometric; maximal contractions; muscle length; negative work; positive work