Details

Autor(en) / Beteiligte

• Stewart, Julian M
• Montgomery, Leslie D
• Glover, June L
• Medow, Marvin S

Titel

Changes in regional blood volume and blood flow during static handgrip

Ist Teil von

• American journal of physiology. Heart and circulatory physiology, 2007-01, Vol.292 (1), p.H215-H223

Ort / Verlag

United States: American Physiological Society

Erscheinungsjahr

2007

Quelle

MEDLINE

Beschreibungen/Notizen

• Department of 1 Pediatrics and 2 Physiology, New York Medical College, Valhalla, New York; and 3 LDM Associates, San Jose, California Submitted 27 June 2006 ; accepted in final form 17 August 2006 Increased blood pressure (BP) and heart rate during exercise characterizes the exercise pressor reflex. When evoked by static handgrip, mechanoreceptors and metaboreceptors produce regional changes in blood volume and blood flow, which are incompletely characterized in humans. We studied 16 healthy subjects aged 20–27 yr using segmental impedance plethysmography validated against dye dilution and venous occlusion plethysmography to noninvasively measure changes in regional blood volumes and blood flows. Static handgrip while in supine position was performed for 2 min without postexercise ischemia. Measurements of heart rate and BP variability and coherence analyses were used to examine baroreflex-mediated autonomic effects. During handgrip exercise, systolic BP increased from 120 ± 10 to 148 ± 14 mmHg, whereas heart rate increased from 60 ± 8 to 82 ± 12 beats/min. Heart rate variability decreased, whereas BP variability increased, and transfer function amplitude was reduced from 18 ± 2 to 8 ± 2 ms/mmHg at low frequencies of 0.1 Hz. This was associated with marked reduction of coherence between BP and heart rate (from 0.76 ± 0.10 to 0.26 ± 0.05) indicative of uncoupling of heart rate regulation by the baroreflex. Cardiac output increased by 18% with a 4.5% increase in central blood volume and an 8.5% increase in total peripheral resistance, suggesting increased cardiac preload and contractility. Splanchnic blood volume decreased reciprocally with smaller decreases in pelvic and leg volumes, increased splanchnic, pelvic and calf peripheral resistance, and evidence for splanchnic venoconstriction. We conclude that the exercise pressor reflex is associated with reduced baroreflex cardiovagal regulation and driven by increased cardiac output related to enhanced preload, cardiac contractility, and splanchnic blood mobilization. exercise pressor reflex; mechanoreflex; metaboreflex Address for reprint requests and other correspondence: J. M. Stewart, Professor of Pediatrics and Physiology, Research Division and Hypotension Laboratory, New York Medical College, Suite 3050, 19 Bradhurst Ave., Hawthorne, NY 10532 (e-mail: stewart{at}nymc.edu )