title: Closed chain assessment of quadriceps activation using the superimposed burst technique.
abstract: The superimposed burst technique is used to estimate quadriceps central activation ratio during a maximal voluntary isometric contraction, which is calculated from force data during an open-chain knee extension task. Assessing quadriceps activation in a closed-chain position would more closely simulate the action of the quadriceps during activity. Our aim was to determine the test-retest reliability of the quadriceps central activation ratio in the closed chain.
  
  
  METHODS
  Twenty-two healthy, active volunteers (13M/12F; age=23.8±3; height=72.7±14.5cm; mass=175.3±9.6kg) were recruited to participate. Knee extension MVIC torque and the peak torque during a superimposed electrical stimulus delivered to the quadriceps during an MVIC were measured to estimate quadriceps CAR. Interclass correlation coefficients were used to assess test-retest reliability between sessions, and Bland-Altman plots to graphically assess agreement between sessions.
  
  
  RESULTS
  Test-retest reliability was fair for CAR (ICC2,k=0.68; P=0.005), with a mean difference of -2.8±10.3%, and limits of agreement ranging -23.1-18.1%.
  
  
  CONCLUSIONS
  CAR calculated using the superimposed burst technique is moderately reliable in a closed-chain position using technique-based instruction. Although acceptable reliability was demonstrated, wide limits of agreement suggest high variability between sessions.
authors.affiliation: Department of Human Services, Kinesiology Program Area, University of Virginia, United States. Electronic address: gen5e@virginia.edu.
authors.forename: Grant E
authors.initials: GE
authors.lastname: Norte
authors.affiliation: Department of Human Services, Kinesiology Program Area, University of Virginia, United States.
authors.forename: Christopher
authors.initials: C
authors.lastname: Kuenze
authors.affiliation: Department of Human Services, Kinesiology Program Area, University of Virginia, United States.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Hart
mesh_terms: D000328:Adult; D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D007717:Knee / Q000502:physiology; D008297:Male; D009068:Movement / Q000502:physiology; D052097:Quadriceps Muscle / Q000502:physiology*; D012016:Reference Values; D015203:Reproducibility of Results; D019415:Torque; D055815:Young Adult
keywords: Central activation ratio; Electrical stimulation; Test–retest reliability