Parasympathetic baroreflexes and heart rate variability during acute stage of sport concussion recovery.

Primary Objective: To assess and compare the parasympathetic state of individuals in healthy vs concussion groups, by measuring cardiovascular metrics under resting and baroreflex conditions using a squat-stand manoeuvre.

Research Design: This was a retrospective mixed-method study, with participants who sustained a medically diagnosed sport concussion (n = 12), being tested within 72-hours post-injury.

Methods And Procedures: Participant's heart rate (Electrocardiogram, ECG) and blood pressure (finger plethysmography) data was collected during rest and during 10-second squat-stands (10SS, 0.05 Hz). Blood pressure and heart rate standard deviation data was analysed in the 0-5 seconds and 6-10 seconds periods of squatting and standing. Resting and baroreflex ECG data were analysed via Fourier Transformations for %Low Frequency and %High Frequency (%LF and %HF).

Results: The control group alleviated more pressure and had a significantly higher standard deviation of heart rate during the 6-10 seconds of squatting (p < 0.05). Overall heart rate standard deviation in the concussion group was significantly lower than healthy controls when standing (p < 0.05). There were no differences in %LF and % HF between groups or between rest and 10SS.

Conclusion: This study provides preliminary evidence that autonomic function is dysregulated following mTBI within the initial 72 hours of injury.