The Effect of Whole-Body Fatigue on King-Devick Test and Balance.

: Fatigue may mimic suboptimal brain functioning seen after a concussion and lead to false-positive King-Devick (K-D) scores and decreased balance. The purpose of this study was to investigate if whole-body fatigue has an effect on K-D scores or postural sway. : A total of 38 healthy participants (20 females; age = 23.5 ± 2.63 y; height = 170 ± 0.1 cm; mass = 75.2 ± 10.3 kg) volunteered for the study. Participants completed the King-Devick (K-D) test and the modified Clinical Test of Sensory Interaction of Balance (mCTSIB) on the Biodex BioSway Portable Balance System prior to and immediately following the completion of a fatigue protocol on a Concept2 Rower. : Half of the participants demonstrated a positive K-D test post-fatigue. Balance scores were poorer post-fatigue. No difference was found between participants based on history of concussion. Among the participants that had a positive post-fatigue K-D test, 71% had also a worse composite sway index score (χ = 6.3, = .02). : Whole-body fatigue may negatively impact a person's ability to perform the K-D test and balance assessments. It is recommended that the athlete is allowed a period of time to accommodate for the acute effects of fatigue before administering these assessments following a suspected concussion.