Effect of hemodilution on maximal oxygen consumption, blood lactate response to exercise and cerebral blood flow in subjects with a high-affinity hemoglobin

The influence of brain norepinephrine on cerebral metabolism and blood flow was examined because exogenous norepinephrine, administered in a way that the blood-brain barrier is bypassed, has been shown to effect pronounced changes in the cerebral circulation. Reserpine (40 mug/kg, by intracarotid infusion) was administered in order to release brain norepinephrine in five anesthetized baboons. Reserpine significantly increased cerebral oxygen consumption (23%) and cerebral blood flow (50%). This response lasted for approximately 60 min. In a further five animals, effects of central beta-adrenoreceptor blockade were studied. Pro pranolol (12 mug/kg-min) produced an immediate, significant reduction in both cerebral oxygen consumption (40%) and cerebral glucose uptake (39%). Cerebral blood flow was reduced minimally. However, the responsiveness of the cerebral circulation to induced hypercapnia was severely attenuated from a gradient of 3.22 before, to 1,11 after, administration. These experiments suggest that central norepinephrine can influence the cerebral circulation primarily through noradrenergic effects on brain metabolism.

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Cerebral Blood Flow and Oxygen Consumption in Man

Physiological Reviews ◽

10.1152/physrev.1959.39.2.183 ◽

1959 ◽

Vol 39 (2) ◽

pp. 183-238 ◽

Cited By ~ 1269

Author(s):

Niels A. Lassen

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Oxygen Consumption

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Effects of a 2-km Swim on Markers of Cycling Performance in Elite Age-Group Triathletes

Sports ◽

10.3390/sports7040082 ◽

2019 ◽

Vol 7 (4) ◽

pp. 82

Author(s):

Jeffrey Rothschild ◽

George H. Crocker

Keyword(s):

Heart Rate ◽

Oxygen Consumption ◽

Blood Lactate ◽

Peak Power ◽

Maximal Oxygen Consumption ◽

Lactate Concentration ◽

Blood Lactate Concentration ◽

Cycling Performance ◽

Age Group

The purpose of this study was to examine the effects of a 2-km swim on markers of subsequent cycling performance in well-trained, age-group triathletes. Fifteen participants (10 males, five females, 38.3 ± 8.4 years) performed two progressive cycling tests between two and ten days apart, one of which was immediately following a 2-km swim (33.7 ± 4.1 min). Cycling power at 4-mM blood lactate concentration decreased after swimming by an average of 3.8% (p = 0.03, 95% CI −7.7, 0.2%), while heart rate during submaximal cycling (220 W for males, 150 W for females) increased by an average of 4.0% (p = 0.02, 95% CI 1.7, 9.7%), compared to cycling without prior swimming. Maximal oxygen consumption decreased by an average of 4.0% (p = 0.01, 95% CI −6.5, −1.4%), and peak power decreased by an average of 4.5% (p < 0.01, 95% CI −7.3, −2.3%) after swimming, compared to cycling without prior swimming. Results from this study suggest that markers of submaximal and maximal cycling are impaired following a 2-km swim.

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