title: The impact of concussion on cardiac autonomic function: A systematic review.
abstract: OBJECTIVE
  To evaluate the evidence regarding the effect of concussion on cardiac autonomic function (CAF).
  
  
  METHODS
  Original research; available in English; included participants with concussion or mild traumatic brain injury (mTBI) and a comparison group; included measures of heart rate (HR) and/or heart rate variability (HRV) as outcomes. Studies of humans (greater than 6 years old) and animals were included. Critical appraisal tools: The Downs and Black (DB) criteria and Structured Effectiveness Quality Evaluation Scale (SEQES).
  
  
  RESULTS
  Nine full-length articles and four abstracts were identified. There is conflicting evidence regarding CAF at rest following concussion. There is evidence of elevated HR and reduced HRV with low-intensity, steady-state exercise up to 10 days following concussion. There was no significant difference in HRV during isometric handgrip testing or HR while performing cognitive tasks following concussion. The validity of current literature is limited by small sample sizes, lack of female or paediatric participants, methodological heterogeneity and lack of follow-up.
  
  
  CONCLUSIONS
  While there is some evidence to suggest CAF is altered during physical activity following concussion, methodological limitations highlight the need for further research. Understanding the effect of concussion on CAF will contribute to the development of more comprehensive concussion management strategies.
authors.affiliation: a Sport Injury Prevention Research Centre, Faculty of Kinesiology , University of Calgary , Calgary , Canada.
authors.forename: Tracy A
authors.initials: TA
authors.lastname: Blake
authors.affiliation: b Department for Health , University of Bath , Bath , UK.
authors.forename: Carly D
authors.initials: CD
authors.lastname: McKay
authors.affiliation: a Sport Injury Prevention Research Centre, Faculty of Kinesiology , University of Calgary , Calgary , Canada.|c University of Calgary Sport Medicine Centre, University of Calgary , Calgary , Canada.
authors.forename: Willem H
authors.initials: WH
authors.lastname: Meeuwisse
authors.affiliation: a Sport Injury Prevention Research Centre, Faculty of Kinesiology , University of Calgary , Calgary , Canada.|d Pediatrics, Alberta Children's Hospital Research Institute for Child & Maternal Health , Faculty of Medicine , Calgary , Canada.|e Community Health Sciences, Faculty of Medicine , University of Calgary , Calgary , Canada.
authors.forename: Carolyn A
authors.initials: CA
authors.lastname: Emery
mesh_terms: D000818:Animals; D017776:Autonomic Pathways / Q000502:physiology; D001924:Brain Concussion / Q000150:complications*; D005260:Female; D006321:Heart / Q000294:innervation* / Q000502:physiology*; D006339:Heart Rate; D006801:Humans; D008297:Male; D051381:Rats; D012146:Rest
keywords: Mild traumatic brain injury; critical appraisal tools; heart rate; heart rate variability; physical activity