title: Can a clinical test of reaction time predict a functional head-protective response?
abstract: OBJECTIVE
  Reaction time is commonly prolonged after a sport-related concussion. Besides being a marker for injury, a rapid reaction time is necessary for protective maneuvers that can reduce the frequency and severity of additional head impacts. The purpose of this study was to determine whether a clinical test of simple visuomotor reaction time predicted the time taken to raise the hands to protect the head from a rapidly approaching ball.
  
  
  METHODS
  Twenty-six healthy adult participants recruited from campus and community recreation and exercise facilities completed two experimental protocols during a single session: a manual visuomotor simple reaction time test (RT(clin)) and a sport-related head-protective response (RT(sprt)). RT(clin) measured the time required to catch a thin vertically oriented device on its release by the tester and was calculated from the distance the device fell before being arrested. RT(sprt) measured the time required to raise the hands from waist level to block a foam tennis ball fired toward the subject's face from an air cannon and was determined using an optoelectronic camera system. A correlation coefficient was calculated between RT(clin) and RT(sprt), with linear regression used to assess for effect modification by other covariates.
  
  
  RESULTS
  A strong positive correlation was found between RT(clin) and RT(sprt) (r = 0.725, P < 0.001) independent of age, gender, height, or weight.
  
  
  CONCLUSIONS
  RT(clin) is predictive of a functional sport-related head-protective response. To our knowledge, this is the first demonstration of a clinical test predicting the ability to protect the head in a simulated sport environment. This correlation with a functional head-protective response is a relevant consideration for the potential use of RT(clin) as part of a multifaceted concussion assessment program.
authors.affiliation: Department of Physical Medicine & Rehabilitation, University of Michigan, Ann Arbor, MI 48108, USA. jeckner@med.umich.edu
authors.forename: James T
authors.initials: JT
authors.lastname: Eckner
authors.forename: David B
authors.initials: DB
authors.lastname: Lipps
authors.forename: Hogene
authors.initials: H
authors.lastname: Kim
authors.forename: James K
authors.initials: JK
authors.lastname: Richardson
authors.forename: James A
authors.initials: JA
authors.lastname: Ashton-Miller
mesh_terms: D000293:Adolescent; D000328:Adult; D001924:Brain Concussion / Q000503:physiopathology / Q000517:prevention & control*; D005260:Female; D006225:Hand / Q000502:physiology*; D006257:Head / Q000503:physiopathology; D006260:Head Protective Devices; D006801:Humans; D008297:Male; D011930:Reaction Time / Q000502:physiology*; D055815:Young Adult