Reductions In Posterior Cerebral Blood Flow Are Susceptible To Orthostatic Stress During Post-exercise Acute Hypotension

PURPOSE: This study aimed to compare the acute effects of different types (treadmill vs. cycle) of moderate-intensity aerobic exercise on cerebral blood flow and cognitive function in young adults.METHODS: By a randomized crossover study design, ten participants were initially assigned to either treadmill exercise (TE; n=5) or cycle ergometer exercise (CE; n=5) and then they performed the other with seven-day wash-out period. Both exercises were implemented at the target heart rate corresponding to 70% of heart rate reserve for 30 minutes. Cognitive function was assessed by the Stroop Color-Word test at pre- and post-exercise. Cerebral blood flow was continuously monitored using near-infrared spectroscopy technique during rest, cognitive function test (CFT), and exercise.RESULTS: There was a significant group by time interaction in tissue saturation index (TSI) (p=.046). Post-hoc analysis presented that TSI at post-exercise CFT was higher than during exercise in TE (p=.02). In both exercises, TSI at pre-exercise CFT significantly increased compared to the resting value (p=.001). Cerebral oxyhemoglobin level was significantly increased during exercise and at post-exercise CFT compared to the resting value in both exercises (p<.001). The reaction time for certain cognitive tasks such as color, word with matched color, word with color interference, and color with word interference was improved after both exercises (p<.05).CONCLUSIONS: One-bout of moderate-intensity aerobic exercise acutely improves cerebral blood flow and cognitive function even in healthy young adults. Exercise types with the same intensity do not seem to make meaningful difference in the positive effects of aerobic exercise.

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REGULATION OF CEREBRAL BLOOD FLOW DURING ORTHOSTATIC STRESS IN SPACE

Medicine & Science in Sports & Exercise ◽

10.1097/00005768-199905001-01703 ◽

1999 ◽

Vol 31 (Supplement) ◽

pp. S338

Author(s):

J H Zuckerman

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Orthostatic Stress

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Changes in cerebral oxygenation and blood flow during LBNP in spinal cord-injured individuals

Journal of Applied Physiology ◽

10.1152/jappl.2001.91.5.2199 ◽

2001 ◽

Vol 91 (5) ◽

pp. 2199-2204 ◽

Cited By ~ 19

Author(s):

Sibrand Houtman ◽

Jorge M. Serrador ◽

Willy N. J. M. Colier ◽

Derek W. Strijbos ◽

Kevin Shoemaker ◽

...

Keyword(s):

Spinal Cord ◽

Blood Flow ◽

Cerebral Blood Flow ◽

Cerebral Oxygenation ◽

Cerebral Blood Flow Velocity ◽

Lower Body Negative Pressure ◽

Systemic Circulation ◽

Orthostatic Stress ◽

Cerebrovascular Regulation ◽

Spinal Cord Injured

Spinal cord-injured (SCI) individuals, having a sympathetic nervous system lesion, experience hypotension during sitting and standing. Surprisingly, they experience few syncopal events. This suggests adaptations in cerebrovascular regulation. Therefore, changes in systemic circulation, cerebral blood flow, and oxygenation in eight SCI individuals were compared with eight able-bodied (AB) individuals. Systemic circulation was manipulated by lower body negative pressure at several levels down to −60 mmHg. At each level, we measured steady-state blood pressure, changes in cerebral blood velocity with transcranial Doppler, and cerebral oxygenation using near-infrared spectroscopy. We found that mean arterial pressure decreased significantly in SCI but not in AB individuals, in accordance with the sympathetic impairment in the SCI group. Cerebral blood flow velocity decreased during orthostatic stress in both groups, but this decrease was significantly greater in SCI individuals. Cerebral oxygenation decreased in both groups, with a tendency to a greater decrease in SCI individuals. Thus present data do not support an advantageous mechanism during orthostatic stress in the cerebrovascular regulation of SCI individuals.

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Cerebral blood flow during orthostasis: role of arterial CO2

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00446.2005 ◽

2006 ◽

Vol 290 (4) ◽

pp. R1087-R1093 ◽

Cited By ~ 46

Author(s):

J. M. Serrador ◽

R. L. Hughson ◽

J. M. Kowalchuk ◽

R. L. Bondar ◽

A. W. Gelb

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Healthy Subjects ◽

Cerebral Arteries ◽

Alveolar Ventilation ◽

Orthostatic Stress ◽

Upright Posture ◽

Head Up Tilt ◽

End Tidal

Reductions in end-tidal Pco2 (PetCO2) during upright posture have been suggested to be the result of hyperventilation and the cause of decreases in cerebral blood flow (CBF). The goal of this study was to determine whether decreases in PetCO2 reflected decreases in arterial Pco2 (PaCO2) and their relation to increases in alveolar ventilation (V̇a) and decreases in CBF. Fifteen healthy subjects (10 women and 5 men) were subjected to a 10-min head-up tilt (HUT) protocol. PaCO2, V̇a, and cerebral flow velocity (CFV) in the middle and anterior cerebral arteries were examined. In 12 subjects who completed the protocol, reductions in PetCO2 and PaCO2 (−1.7 ± 0.5 and −1.1 ± 0.4 mmHg, P < 0.05) during minute 1 of HUT were associated with a significant increase in V̇a (+0.7 ± 0.3 l/min, P < 0.05). However, further decreases in PaCO2 (−0.5 ± 0.5 mmHg, P < 0.05), from minute 1 to the last minute of HUT, occurred even though V̇a did not change significantly (−0.2 ± 0.3 l/min, P = not significant). Similarly, CFV in the middle and anterior cerebral arteries decreased (−7 ± 2 and −8 ± 2%, P < 0.05) from minute 1 to the last minute of HUT, despite minimal changes in PaCO2. These data suggest that decreases in PetCO2 and PaCO2 during upright posture are not solely due to increased V̇a but could be due to ventilation-perfusion mismatch or a redistribution of CO2 stores. Furthermore, the reduction in PaCO2 did not fully explain the decrease in CFV throughout HUT. These data suggest that factors in addition to a reduction in PaCO2 play a role in the CBF response to orthostatic stress.

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Effects of age and exercise on cerebral blood flow responses to orthostatic stress

10.31274/rtd-20200803-63 ◽

2002 ◽

Author(s):

Kelly Ann Erpelding

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Orthostatic Stress

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The cerebrovascular response to lower-body negative pressure vs. head-up tilt

Journal of Applied Physiology ◽

10.1152/japplphysiol.00797.2016 ◽

2017 ◽

Vol 122 (4) ◽

pp. 877-883 ◽

Cited By ~ 10

Author(s):

Anne-Sophie G. T. Bronzwaer ◽

Jasper Verbree ◽

Wim J. Stok ◽

Mat J. A. P. Daemen ◽

Mark A. van Buchem ◽

...

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Negative Pressure ◽

Cerebral Blood Flow Velocity ◽

Lower Body Negative Pressure ◽

Orthostatic Stress ◽

Lower Body ◽

Head Up Tilt ◽

End Tidal ◽

Pronounced Reduction

Lower-body negative pressure (LBNP) has been proposed as a MRI-compatible surrogate for orthostatic stress. Although the effects of LBNP on cerebral hemodynamic behavior have been considered to reflect those of orthostatic stress, a direct comparison with actual orthostasis is lacking. We assessed the effects of LBNP (−50 mmHg) vs. head-up tilt (HUT; at 70°) in 10 healthy subjects (5 female) on transcranial Doppler-determined cerebral blood flow velocity (CBF v) in the middle cerebral artery and cerebral perfusion pressure (CPP) as estimated from the blood pressure signal (finger plethysmography). CPP was maintained during LBNP but decreased after 2 min in response to HUT, leading to an ~15% difference in CPP between LBNP and HUT ( P ≤ 0.020). Mean CBF v initially decreased similarly in response to LBNP and for HUT, but, from minute 3 on, the decline became ~50% smaller ( P ≤ 0.029) during LBNP. The reduction in end-tidal Pco2 partial pressure (PetCO2) was comparable but with an earlier return toward baseline values in response to LBNP but not during HUT ( P = 0.008). We consider the larger decrease in CBF v during HUT vs. LBNP attributable to the pronounced reduction in PetCO2 and to gravitational influences on CPP, and this should be taken into account when applying LBNP as an MRI-compatible orthostatic stress modality. NEW & NOTEWORTHY Lower-body negative pressure (LBNP) has the potential to serve as a MRI-compatible surrogate of orthostatic stress but a comparison with actual orthostasis was lacking. This study showed that the pronounced reduction in end-tidal Pco2 together with gravitational effects on the brain circulation lead to a larger decline in cerebral blood flow velocity in response to head-up tilt than during lower-body negative pressure. This should be taken into account when employing lower-body negative pressure as MRI-compatible alternative to orthostatic stress.

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