Relationship Between Ventilatory Threshold and Cerebral Blood Flow During Maximal Exercise in Humans

Little is known about the response of the cerebrovasculature to acute exercise in children and how these responses might differ with adults. Therefore, we compared changes in middle cerebral artery blood velocity (MCAVmean), end-tidal Pco2 ([Formula: see text]), blood pressure, and minute ventilation (V̇e) in response to incremental exercise between children and adults. Thirteen children [age: 9 ± 1 (SD) yr] and thirteen sex-matched adults (age: 25 ± 4 yr) completed a maximal exercise test, during which MCAVmean, [Formula: see text], and V̇e were measured continuously. These variables were measured at rest, at exercise intensities specific to individual ventilatory thresholds, and at maximum. Although MCAVmean was higher at rest in children compared with adults, there were smaller increases in children (1–12%) compared with adults (12–25%) at all exercise intensities. There were alterations in [Formula: see text] with exercise intensity in an age-dependent manner [ F(2.5,54.5) = 7.983, P < 0.001; η2 = 0.266], remaining stable in children with increasing exercise intensity (37–39 mmHg; P > 0.05) until hyperventilation-induced reductions following the respiratory compensation point. In adults, [Formula: see text] increased with exercise intensity (36–45 mmHg, P < 0.05) until the ventilatory threshold. From the ventilatory threshold to maximum, adults showed a greater hyperventilation-induced hypocapnia than children. These findings show that the relative increase in MCAVmean during exercise was attenuated in children compared with adults. There was also a weaker relationship between MCAVmean and [Formula: see text] during exercise in children, suggesting that cerebral perfusion may be regulated by different mechanisms during exercise in the child. NEW & NOTEWORTHY These findings provide the first direct evidence that exercise increases cerebral blood flow in children to a lesser extent than in adults. Changes in end-tidal CO2 parallel changes in cerebral perfusion in adults but not in children, suggesting age-dependent regulatory mechanisms of cerebral blood flow during exercise.

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Dehydration affects cerebral blood flow but not its metabolic rate for oxygen during maximal exercise in trained humans

The Journal of Physiology ◽

10.1113/jphysiol.2014.272104 ◽

2014 ◽

Vol 592 (14) ◽

pp. 3143-3160 ◽

Cited By ~ 53

Author(s):

Steven J. Trangmar ◽

Scott T. Chiesa ◽

Christopher G. Stock ◽

Kameljit K. Kalsi ◽

Niels H. Secher ◽

...

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Metabolic Rate ◽

Maximal Exercise

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The Regulation of Cerebral Blood Flow During Recovery from Dynamic Exercise in Humans

Medicine & Science in Sports & Exercise ◽

10.1249/00005768-200605001-01755 ◽

2006 ◽

Vol 38 (Supplement) ◽

pp. S196

Author(s):

Shigehiko Ogoh ◽

James P. Fisher ◽

Sushmita Purkayastha ◽

Ellen A. Dawson ◽

Michael J. White ◽

...

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Dynamic Exercise ◽

Exercise In Humans

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Cerebral blood flow and oxygenation at maximal exercise: The effect of clamping carbon dioxide

Respiratory Physiology & Neurobiology ◽

10.1016/j.resp.2010.09.011 ◽

2011 ◽

Vol 175 (1) ◽

pp. 176-180 ◽

Cited By ~ 28

Author(s):

J. Tod Olin ◽

Andrew C. Dimmen ◽

Andrew W. Subudhi ◽

Robert C. Roach

Keyword(s):

Carbon Dioxide ◽

Blood Flow ◽

Cerebral Blood Flow ◽

Maximal Exercise

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Evaluating the methods used for measuring cerebral blood flow at rest and during exercise in humans

European Journal of Applied Physiology ◽

10.1007/s00421-018-3887-y ◽

2018 ◽

Vol 118 (8) ◽

pp. 1527-1538 ◽

Cited By ~ 9

Author(s):

Michael M. Tymko ◽

Philip N. Ainslie ◽

Kurt J. Smith

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Exercise In Humans

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Effects of ATP-induced leg vasodilation on V̇o2 peak and leg O2 extraction during maximal exercise in humans

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00746.2005 ◽

2006 ◽

Vol 291 (2) ◽

pp. R447-R453 ◽

Cited By ~ 65

Author(s):

J. A. L. Calbet ◽

C. Lundby ◽

M. Sander ◽

P. Robach ◽

B. Saltin ◽

...

Keyword(s):

Blood Flow ◽

Maximal Exercise ◽

Muscle Fibers ◽

Isotonic Saline ◽

Whole Body ◽

Active Muscle ◽

Vascular Conductance ◽

Exercise Tests ◽

Leg Blood Flow ◽

Exercise In Humans

During maximal whole body exercise V̇o2 peak is limited by O2 delivery. In turn, it is though that blood flow at near-maximal exercise must be restrained by the sympathetic nervous system to maintain mean arterial pressure. To determine whether enhancing vasodilation across the leg results in higher O2 delivery and leg V̇o2 during near-maximal and maximal exercise in humans, seven men performed two maximal incremental exercise tests on the cycle ergometer. In random order, one test was performed with and one without (control exercise) infusion of ATP (8 mg in 1 ml of isotonic saline solution) into the right femoral artery at a rate of 80 μg·kg body mass−1·min−1. During near-maximal exercise (92% of V̇o2 peak), the infusion of ATP increased leg vascular conductance (+43%, P < 0.05), leg blood flow (+20%, 1.7 l/min, P < 0.05), and leg O2 delivery (+20%, 0.3 l/min, P < 0.05). No effects were observed on leg or systemic V̇o2. Leg O2 fractional extraction was decreased from 85 ± 3 (control) to 78 ± 4% (ATP) in the infused leg ( P < 0.05), while it remained unchanged in the left leg (84 ± 2 and 83 ± 2%; control and ATP; n = 3). ATP infusion at maximal exercise increased leg vascular conductance by 17% ( P < 0.05), while leg blood flow tended to be elevated by 0.8 l/min ( P = 0.08). However, neither systemic nor leg peak V̇o2 values where enhanced due to a reduction of O2 extraction from 84 ± 4 to 76 ± 4%, in the control and ATP conditions, respectively ( P < 0.05). In summary, the V̇o2 of the skeletal muscles of the lower extremities is not enhanced by limb vasodilation at near-maximal or maximal exercise in humans. The fact that ATP infusion resulted in a reduction of O2 extraction across the exercising leg suggests a vasodilating effect of ATP on less-active muscle fibers and other noncontracting tissues and that under normal conditions these regions are under high vasoconstrictor influence to ensure the most efficient flow distribution of the available cardiac output to the most active muscle fibers of the exercising limb.

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Coupling between the blood lactate-to-pyruvate ratio and MCA Vmean at the onset of exercise in humans

Journal of Applied Physiology ◽

10.1152/japplphysiol.00468.2009 ◽

2009 ◽

Vol 107 (6) ◽

pp. 1799-1805 ◽

Cited By ~ 7

Author(s):

Peter Rasmussen ◽

Camilla A. Madsen ◽

Henning B. Nielsen ◽

Morten Zaar ◽

Albert Gjedde ◽

...

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Brain Tissue ◽

Oxygen Tension ◽

Redox State ◽

Mean Flow ◽

Cerebral Capillary ◽

Calculated Average ◽

Exercise In Humans ◽

Pyruvate Ratio

Activation-induced increase in cerebral blood flow is coupled to enhanced metabolic activity, maybe with brain tissue redox state and oxygen tension as key modulators. To evaluate this hypothesis at the onset of exercise in humans, blood was sampled at 0.1 to 0.2 Hz from the radial artery and right internal jugular vein, while middle cerebral artery mean flow velocity (MCA Vmean) was recorded. Both the arterial and venous lactate-to-pyruvate ratio increased after 10 s ( P < 0.05), and the arterial ratio remained slightly higher than the venous ( P < 0.05). The calculated average cerebral capillary oxygen tension decreased by 2.7 mmHg after 5 s ( P < 0.05), while MCA Vmean increased only after 30 s. Furthermore, there was an unaccounted cerebral carbohydrate uptake relative to the uptake of oxygen that became significant 50 s after the onset of exercise. These findings support brain tissue redox state and oxygenation as potential modulators of an increase in cerebral blood flow at the onset of exercise.

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