Heart Rate Variability in Adolescents Following a Sport-Related Concussion

Abstract

Sport-related concussion (SRC) or mild traumatic brain injury symptoms are usually resolved within 2 weeks after the injury, but a growing body of evidence suggests persistent deficits of the central nervous system months and years after the injury. A concussion could also alter the autonomic nervous system (ANS), which regulates heartbeat, blood pressure, respiration, thermoregulation and circadian rhythm. A simple and non-invasive way to evaluate ANS function is to measure heart rate variability (HRV). HRV, the variation of the beat-to-beat interval, is one of the physiological manifestations of the ANS. HRV was showed as a reliable marker of SNA dysfunction in patients who suffered from a traumatic brain injury. However, very few studies evaluated the effects of sport-related concussion on HRV and all of them only involved adults. Together, these studies suggest ANS alteration days to months after the injury. Nonetheless, the outcomes of concussion in youth regarding HRV and ANS remain unexplored and unknown. PURPOSE: Therefore, we sought to evaluate the influence of concussion on HRV in adolescents aged from 11 to 17 years. METHOD: To do so, we tested 30 hockey players with a history of concussion (HC) and 22 controls without a history of concussion (NHC). Time since injury was on average 25 months (±24,5). For each participant, we recorded the R-R interval with a chest strap heart rate monitor during all the session. After 5 minutes of sitting rest, the participants exercised on a cycle ergometer during 20 minutes between 60 and 70% of their theoretical maximal heart, following a gradual load increase. Then, there was a cool down for 2 minutes on the ergocycle and a rest period in sitting position for 10 minutes. We compared the HRV of the HC and the NHC during 4 minutes of the pre-exercise rest and 4 minutes of the post-exercise rest. RESULTS: We found no significant difference in any HRV measure of the temporal or frequency domains, neither did we find any difference in the non-parametric measures of HRV (p > 0.05). CONCLUSION: Our results suggest that, if there are ANS deficits in adolescents following a concussion, they do not manifest themselves under the conditions that we tested.