TY - JOUR
T1 - Influence of head-down and lateral decubitus neck flexion on heart rate variability
AU - Lee, C. M.
AU - Wood, R. H.
AU - Welsch, M. A.
PY - 2001
Y1 - 2001
N2 - The purpose of this study was to examine the response of heart rate variability (HRV), a noninvasive index of autonomic control, to head-down neck flexion (HDNF), which engages both otoliths and neck muscle afferents, and to lateral decubitus neck flexion (LNF), in which neck afferents are activated, whereas otolith afferent input is not. HRV and forearm blood flow were evaluated in participants lying prone, during HDNF, lying in the lateral decubitus position, and during LNF. Compared with the prone position, HDNF resulted in lower high-frequency (46.9 ± 7.1 vs. 62.3 ± 6.2) and higher low-frequency (53.1 ± 7.1 vs. 37.7 ± 6.2) power, expressed as normalized units, along with higher low-frequency-to-high-frequency ratio (1.65 ± 0.3 vs. 0.78 ± 0.2), whereas LNF resulted in no alterations in HRV indexes. Furthermore, there were no significant differences in forearm blood flow or vascular resistance among any of the positions. Our data suggest that otolith organs influence autonomic modulation of the heart, supporting previous studies reporting that HDNF elicits increased sympathetic outflow. These data further suggest that HDNF results in a parasympathetic withdrawal from the heart in addition to sympathetic activation.
AB - The purpose of this study was to examine the response of heart rate variability (HRV), a noninvasive index of autonomic control, to head-down neck flexion (HDNF), which engages both otoliths and neck muscle afferents, and to lateral decubitus neck flexion (LNF), in which neck afferents are activated, whereas otolith afferent input is not. HRV and forearm blood flow were evaluated in participants lying prone, during HDNF, lying in the lateral decubitus position, and during LNF. Compared with the prone position, HDNF resulted in lower high-frequency (46.9 ± 7.1 vs. 62.3 ± 6.2) and higher low-frequency (53.1 ± 7.1 vs. 37.7 ± 6.2) power, expressed as normalized units, along with higher low-frequency-to-high-frequency ratio (1.65 ± 0.3 vs. 0.78 ± 0.2), whereas LNF resulted in no alterations in HRV indexes. Furthermore, there were no significant differences in forearm blood flow or vascular resistance among any of the positions. Our data suggest that otolith organs influence autonomic modulation of the heart, supporting previous studies reporting that HDNF elicits increased sympathetic outflow. These data further suggest that HDNF results in a parasympathetic withdrawal from the heart in addition to sympathetic activation.
KW - Autonomic
KW - Muscle afferents
KW - Otoliths
UR - http://www.scopus.com/inward/record.url?scp=0035159662&partnerID=8YFLogxK
U2 - 10.1152/jappl.2001.90.1.127
DO - 10.1152/jappl.2001.90.1.127
M3 - Article
C2 - 11133902
AN - SCOPUS:0035159662
SN - 8750-7587
VL - 90
SP - 127
EP - 132
JO - Journal of Applied Physiology
JF - Journal of Applied Physiology
IS - 1
ER -