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History of multiple sport-related concussions alters variability of heart rate response to activity
  1. Alexander D Wright1,2,3,4,
  2. Harjas S Grewal5,
  3. Jonathan D Smirl1,
  4. Kelsey Bryk1,
  5. Paul van Donkelaar1
  1. 1School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, Canada
  2. 2University of British Columbia, Vancouver, Canada
  3. 3Southern Medical Program, University of British Columbia Okanagan, Kelowna, Canada
  4. 4Department of Experimental Medicine, Faculty of Medicine, University of British Columbia, Vancouver, Canada
  5. 5Northern Medical Program, University of Northern British Columbia, Prince George, Canada

Abstract

Objective To examine the effect of multiple previous concussions on heart rate variability (HRV) in contact-sport athletes.

Design Retrospective Cohort.

Setting Laboratory.

Participants 136 male elite contact-sport (hockey and football) athletes were recruited for this study. Forty-one had no previous concussion history (Hx-), while nineteen had a history of three or more concussions (Hx+). All testing was preformed prior to the start of the competitive season

Interventions HRV was assessed during 5-minutes of quiet stance, and while actively squatting at 0.10 Hz via a 3-lead electrocardiogram, using Kubios software. Independent variables included condition (rest vs active) and group (Hx+ vs Hx-)

Outcome measures Time-Domain: square root of mean squared differences of successive R-R intervals (RMSSD), percentage of successive R-R intervals that differ by more than 50 milliseconds (pNN50). Frequency-Domain: total power.

Main results Mixed ANOVA revealed repeated squat-stand manoeuvres challenged the autonomic system, increasing total power by 2477 milliseconds2 (95% CI: 1153–3801, p<0.001). A significant interaction effect was observed for RMSSD (p=0.031) and pNN50 (p=0.012), characterised by a greater increase in HRV in the Hx+ group than in Hx- from rest to squatting (95%CIs for group differences, RMSSD: 13.2–26.3 ms, p=0.006; pNN50: 3.6–15.1%, p=0.002)

Conclusions A history of multiple sport-related concussions impairs the ability of the autonomic system to respond to an everyday stressor applied to the cardiovascular system (squatting and standing). This is an important finding, as it reveals that cumulative concussions may impart long-term impairments in the ability to accurately regulate the autonomic system.

Competing interests None.

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