Spontaneous Cardiovagal Baroreflex Sensitivity Following A Bout Of Subconcussive Head Impacts Is Not Altered

BACKGROUND: Subconcussive head impacts (SHI) impair vestibular and ocular function, similar to a concussion. Some evidence indicates that concussion impairs spontaneous cardiovagal baroreflex sensitivity (scBRS). PURPOSE: Test the hypothesis that a bout of SHI would impair scBRS sensitivity in young healthy participants. METHODS: 14 healthy participants (age: 19 ± 2 y; 3 women) with 3+ y of soccer heading experience completed two experimental conditions in a randomized crossover design. 20 soccer headings were used to induce repetitive SHI and 20 soccer kicks were used as the control condition. A soccer ball was projected from a soccer JUGS machine (velocity: 40 km/h; distance: 12.2 m) every 30 s for both conditions. Baseline measurements preceded the interventions with follow-up measurements at 2 h-, 24 h-, and 72 h- post. scBRS was assessed using the sequence method (Up, Down, Pooled) from continuous heart rate (HR; 3-lead ECG) and blood pressure (photoplethysmography) measurements recorded during 5 min of quiet, paced breathing (15 breaths/min). Data are presented as mean ± SD. RESULTS: There was an interaction for mean arterial pressure (p = 0.01), which was greater in heading vs. kicking at 2 h (102 ± 15 mmHg vs. 91 ± 10 mmHg; p = 0.02). There was an interaction for diastolic blood pressure (p = 0.02), which was greater in heading vs. kicking at 2 h (83 ± 16 mmHg vs. 66 ± 10 mmHg; p = 0.03). No differences were observed for HR (condition: p = 0.55; interaction: p = 0.34), systolic blood pressure (condition: p = 0.62; interaction: p = 0.11), scBRSUp (condition: p = 0.12; interaction: 0.53) scBRSDown (condition: p = 0.19; interaction: 0.39), or scBRSPooled (condition: p = 0.14; interaction: p = 0.45). CONCLUSIONS: Although mean arterial pressure and diastolic blood pressure are elevated following an acute bout of laboratory-controlled SHI, cardiovagal baroreflex control of blood pressure does not appear to be altered.