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Introduction: Beetroot juice (BRJ) improves peripheral endothelial function and vascular compliance, likely due to increased nitric oxide bioavailability. It is unknown if BRJ alters cerebrovascular function and cardiovagal baroreflex control in healthy individuals., Purpose: We tested the hypotheses that BRJ consumption improves cerebral autoregulation (CA) and cardiovagal baroreflex sensitivity (cBRS) during lower-body negative pressure (LBNP)., Methods: Thirteen healthy adults (age: 26 ± 4 years; 5 women) performed oscillatory (O-LBNP) and static LBNP (S-LBNP) before (PRE) and 3 h after consuming 500 mL of BRJ (POST). Participants inhaled 3% CO 2 (21% O 2 , 76% N 2 ) during a 5 min baseline and throughout LBNP to attenuate reductions in end-tidal CO 2 tension (PETCO 2 ). O-LBNP was conducted at ∼0.02 Hz for six cycles (-70 mmHg), followed by a 3-min recovery before S-LBNP (-40 mmHg) for 7 min. Beat-to-beat middle cerebral artery blood velocity (MCAv) (transcranial Doppler) and blood pressure were continuously recorded. CA was assessed using transfer function analysis to calculate coherence, gain, and phase in the very-low-frequency (VLF; 0.020-0.070 Hz) and low-frequency bands (LF; 0.07-0.20 Hz). cBRS was calculated using the sequence method. Comparisons between POST vs. PRE are reported as mean ± SD., Results: During O-LBNP, coherence VLF was greater at POST (0.55 ± 0.06 vs. 0.46 ± 0.08; P < 0.01), but phase VLF ( P = 0.17) and gain VLF ( P = 0.69) were not different. Coherence LF and phase LF were not different, but gain LF was lower at POST (1.03 ± 0.20 vs. 1.12 ± 0.30 cm/s/mmHg; P = 0.05). During S-LBNP, CA was not different in the VLF or LF bands (all P > 0.10). Up-cBRS and Down-cBRS were not different during both LBNP protocols., Conclusion: These preliminary data indicate that CA and cBRS during LBNP in healthy, young adults is largely unaffected by an acute bolus of BRJ., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Worley, Reed, Chapman, Kueck, Seymour, Fitts, Zazulak, Schlader and Johnson.)

Chronic consumption of sugar- and artificially-sweetened beverages (SSB and ASB) are associated with an increased risk of stroke but it is unclear how acute consumption influences cerebral vascular function. Purpose: We hypothesized that: (1) acute consumption of SSB and ASB would augment dynamic cerebral autoregulation (dCA) and attenuate cerebral vascular reactivity to hypercapnia (CVR CO2 ) compared to water; and (2) dCA and CVR CO2 would be attenuated with SSB compared to ASB and water. Methods: Twelve healthy adults (age: 23 ± 2 years, four females) completed three randomized trials where they drank 500 ml of water, SSB (Mountain Dew ® ), or ASB (Diet Mountain Dew ® ). We measured mean arterial pressure (MAP), middle and posterior cerebral artery blood velocities (MCAv and PCAv), and end-tidal CO 2 tension (PETCO 2 ). Cerebral vascular conductance was calculated as cerebral artery blood velocity/MAP (MCAc and PCAc). Twenty min after consumption, participants completed a 5 min baseline, and in a counterbalanced order, a CVR CO2 test (3%, 5%, and 7% CO 2 in 3 min stages) and a dCA test (squat-stand tests at 0.10 Hz and 0.05 Hz for 5 min each) separated by 10 min. CVR CO2 was calculated as the slope of the linear regression lines of MCAv and PCAv vs. PETCO 2 . dCA was assessed in the MCA using transfer function analysis. Coherence, gain, and phase were determined in the low frequency (LF; 0.07-0.2 Hz) and very low frequency (VLF; 0.02-0.07 Hz). Results: MCAv and MCAc were lower after SSB (54.11 ± 12.28 cm/s, 0.58 ± 0.15 cm/s/mmHg) and ASB (51.07 ± 9.35 cm/s, 0.52 ± 1.0 cm/s/mmHg) vs. water (62.73 ± 12.96 cm/s, 0.67 ± 0.11 cm/s/mmHg; all P < 0.035), respectively. PCAc was also lower with the ASB compared to water ( P = 0.007). MCA CVR CO2 was lower following ASB (1.55 ± 0.38 cm/s/mmHg) vs. water (2.00 ± 0.57 cm/s/mmHg; P = 0.011) but not after SSB (1.90 ± 0.67 cm/s/mmHg; P = 0.593). PCA CVR CO2 did not differ between beverages ( P > 0.853). There were no differences between beverages for coherence ( P ≥ 0.295), gain ( P ≥ 0.058), or phase ( P ≥ 0.084) for either frequency. Discussion: Acute consumption of caffeinated SSB and ASB resulted in lower intracranial artery blood velocity and conductance but had a minimal effect on cerebral vascular function as only MCA CVR CO2 was altered with the ASB compared to water., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Reed, Worley, Kueck, Pietrafasa, Schlader and Johnson.)

Introduction: Blunted cardiac autonomic nervous system (ANS) responses, quantified using heart rate variability (HRV), have been reported after sport-related concussion (SRC). Research suggests this persists beyond clinical recovery. This study compared cardiac parasympathetic responses in student athletes with a remote history of SRC (> 1-year ago, Concussion History: CH) with those who reported no lifetime history of SRC (Concussion Naïve: CN). Design: Retrospective nested case-control. Setting: University laboratory. Patients or Other Participants: CH ( n = 9, 18.3 ± 2 years, 44% male, median 2 years since injury) were student athletes with a remote history of concussion(s) from more than 1 year ago. CN ( n = 21, 16.7 ± 3 years, 67% male) were student athletes with no lifetime history of concussion. Exclusion criteria included taking medications that could affect ANS function, history of concussion within the past year, persistent concussion symptoms, lifetime history of moderate to severe brain injury, and lifetime history of more than 3 concussions. Material and Methods: Participants performed the Face Cooling (FC) test for 3-min after 10-min of supine rest while wearing a 3-lead electrocardiogram in a controlled environment. Outcome Measures: Heart rate (HR), R-R interval (RRI), root mean square of the successive differences (RMSSD) of RRI, high frequency (HF) and low frequency to HF (LF:HF) ratios. Results: At baseline, CH had a lower resting HR than CN (62.3 ± 11 bpm vs. 72.9 ± 12, p = 0.034). CH had a different HR response to FC than CN (+8.9% change from baseline in CH vs. -7.5% in CN, p = 0.010). CH also had a smaller RMSSD increase to FC than CN (+31.8% change from baseline in CH vs. +121.8% in CN, p = 0.048). There were no significant group differences over time in RRI ( p = 0.106), HF ( p = 0.550) or LF:HF ratio ( p = 0.053). Conclusion: Asymptomatic student athletes with a remote history of concussion had a blunted cardiac parasympathetic response to FC when compared with athletes with no lifetime history of concussion. These data suggest that an impaired autonomic response to a physiological stressor persists after clinical recovery from SRC for longer than previously reported., (Copyright © 2020 Haider, Johnson, Horn, Leddy, Wilber, Reed, O'Leary, Bloomfield, Decezaro and Willer.)