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Global Switch Cost as an Index for Concussion Assessment: Reliability and Stability


Medicine & Science in Sports & Exercise: June 2013 - Volume 45 - Issue 6 - p 1038–1042
doi: 10.1249/MSS.0b013e318281e1fb
Clinical Sciences

Purpose 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 (M age = 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.

University of Georgia, Department of Kinesiology, Athens, GA

Address for correspondence: Phillip D. Tomporowski, Ph.D., Department of Kinesiology, University of Georgia, 330 River Road, Athens, GA 30602; E-mail:

Submitted for publication August 2012.

Accepted for publication December 2012.

©2013The American College of Sports Medicine