title: Global switch cost as an index for concussion assessment: reliability and stability.
abstract: OBJECTIVE
  The objective of this study is to determine the stability and sensitivity of a dual-task (DT) methodology that can be used to assess the effects of concussion in athletes.
  
  
  METHODS
  Fifty-nine healthy young adults (Mage = 20.32 ± 1.84 yr, 19 males) who volunteered to participate completed auditory switch tasks that varied in length (30, 40, and 60 items) at baseline, 1 wk later, and approximately 7 months later. During sessions 2 and 3, the participants completed one of three switch tasks while concurrently performing a modified Harvard Step Test. Global switch cost indices and percentage error were calculated for each switch task. The stability reliability of the global switch cost indices was assessed under single-task conditions, and the sensitivity of the global switch costs to interference effects was assessed under DT conditions.
  
  
  RESULTS
  The stability reliability was 0.64, 0.84, and 0.83 for the 30-, 40-, and 60-item tests, respectively. ANOVA revealed a main effect for condition (single task vs DT) for both global switch costs (F(1,55) = 44.53, P < 0.0001) and percentage error (F(1,56) = 64.69, P < 0.001). The magnitude of the global switch cost interference effects was nearly identical across the three DT conditions.
  
  
  CONCLUSIONS
  The current concussion testing models test athletes' cognitive and physical function in isolation. The stability reliability of the global switch cost index obtained under DT conditions suggests that it may be a useful measure for clinicians. The DT paradigm presents another test methodology that may be useful for making return-to-play decisions as part of a comprehensive concussion management plan.
authors.affiliation: University of Georgia, Department of Kinesiology, Athens, GA 30602, USA.
authors.forename: Michelle S
authors.initials: MS
authors.lastname: Okumura
authors.forename: Stephanie L
authors.initials: SL
authors.lastname: Cooper
authors.forename: Michael S
authors.initials: MS
authors.lastname: Ferrara
authors.forename: Phillip D
authors.initials: PD
authors.lastname: Tomporowski
mesh_terms: D000704:Analysis of Variance; D001924:Brain Concussion / Q000175:diagnosis* / Q000523:psychology; D003071:Cognition; D056344:Executive Function; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013647:Task Performance and Analysis; D055815:Young Adult