Heart rate variability reductions following a season of sub-concussive head hits are related to the magnitude of impacts experienced. Issue 11 (25th May 2017)

• Record Type: Journal Article
• Authors: Smirl, Jonathan D; Wright, Alexander D; Grewal, Harjas S; Jakovac, Michael; Bryk, Kelsey; Donkelaar, Paul van
• Is Part Of: British journal of sports medicine. Volume 51:Issue 11(2017)
• Page Start: A30
• Page End: A30
• Publication Date: 2017-05-25
• Subjects: Sports medicine -- Periodicals; 617.1027
• DOI: 10.1136/bjsports-2016-097270.76
• Languages: English
• ISSNs: 0306-3674

Abstract

Abstract : Objective: To examine the effect of repetitive contact sport-related head trauma on indices ofheart rate variability (HRV). Design: Prospective Cohort. Setting: Laboratory. Participants: Forty-ninemale contact-sport (hockey or football) and four non-contact control athletes (age range: 17–22). Intervention: Prior to (T1) and upon completion of (T2) the competitive athletic season, a three-lead electrocardiogram and Kubios software (Kuopio, Finland) were used to assess heart rate variability during 5-minutes of quiet stance and while actively squatting at 0.10 Hz. Independent variables included condition (rest-vs-active) and time (T1-vs-T2). 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); Non-Linear: approximateentropy (ApEn). In a subset of participants (n=29) biomechanical head-impact exposure data was estimated usingthe xPatch (X2 Biosystems), affixed to the right mastoid. Main results: RM-ANOVA indicateda significant main effect of timein contact sport but not control athletes (all p>0.133). HRV metrics were decreased post-season relative to baseline (95% CI:s for differences: MeanRR4–48 ms, p=0.045; RMSSD 1–9 ms, p=0.018; pNN50 0.689–5.98, p=0.010; ApEn 0.022–0.163, p=0.044). Significant correlations were observed between the average peak linear acceleration per hit experienced and the change in MeanRR(R²=0.1382), and RMSSD (R²=0.1525). Conclusions: Exposure to repetitive subconcussive impacts overone season of contact-sport leads to decreases in heart rate variability. The magnitude of HRV reduction is related to the average magnitude of the linear component of hits to the head experienced during play Competing interests: None.