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Effect of dynamic exercise on human carotid-cardiac baroreflex latencyWe compared the beat-to-beat responses of heart rate (HR) after brief activation of carotid baroreceptors in resting humans with the responses obtained during mild-to-moderate levels of dynamic exercise [25 and 50% of peak O2 uptake (VO2peak)] to investigate the effect of exercise on baroreflex latency. Carotid baroreceptors were activated by a pressure pulse (5 s) of neck suction (NS, -80 Torr) and neck pressure (NP, +40 Torr) during held expiration. At rest the peak change in HR to NS/NP occurred during the first several heartbeats (1st-3rd beat), whereas during mild and moderate exercise peak HR responses occurred near the end of the NS/NP pulse (6th-8th beat). In contrast, time (s) to the peak change in HR was not different between rest and exercise (P > 0.05). Reflex tachycadia to NP progressively decreased during exercise (17 +/- 3, 10 +/- 1, and 4 +/- 1% of control, rest vs. 25% VO2peak, vs. 50% VO2peak, respectively, P < 0.05), and a strong positive correlation was found between the magnitude of the reflex tachycardia and a measure of HR variability (cardiac vagal tone index, r = 0.74, P < 0.0001). Reflex bradycardia to NS gradually increased during exercise (13 +/- 2, 17 +/- 2, and 18 +/- 2% of control, rest vs. 25% VO2peak, vs. 50% VO2peak, respectively, P = 0.10) and was negatively correlated with cardiac vagal tone (r = 0.42, P < 0.06).(ABSTRACT TRUNCATED AT 250 WORDS).
Document ID
20050000221
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Potts, J. T.
(University of North Texas Health Science Center Fort Worth 76107)
Raven, P. B.
Date Acquired
August 22, 2013
Publication Date
March 1, 1995
Publication Information
Publication: The American journal of physiology
Volume: 268
Issue: 3 Pt 2
ISSN: 0002-9513
Subject Category
Aerospace Medicine
Funding Number(s)
CONTRACT_GRANT: HL-43202
CONTRACT_GRANT: HL-45547
Distribution Limits
Public
Copyright
Other
Keywords
NASA Program Space Physiology and Countermeasures
NASA Discipline Cardiopulmonary
Non-NASA Center
NASA Discipline Number 14-10

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