Head and body positions affect thermoregulatory tonus in deltoid
muscles.
Meigal, Alexander Yu., Yuri V. Lupandin, and Osmo Hanninen.
Department of Physiology, University of Petrozavodsk, 185640, Lenin
Str., 33, Russian Federation; Department of Physiology, University of
Kuopio, FIN2D70211, Kuopio, Finland
APStracts 2:0526A, 1995.
Electromyogram was recorded from both deltoid muscles (DMs) when
subjects were sitting and standing, and during lateral head bends at
different cold sensations in order to clarify the role of head and
body positions in the thermoregulatory tonus. At room temperature
(+22oC) neither EMG related to thermoregulatory muscle tonus (TMT)
nor changes of EMG intensity were observed during changes of posture.
At cold temperature (+5oC) when subjects felt slightly cold or cold,
averaged surface EMG intensity of TMT was around 22D3 mkV during
sitting with the head held upright. EMG of TMT was 7.23+/2D2.99 mkV
in subjects sitting with the upright head when feeling cold and
extremely cold, and it increased up to 14.75+/2D5.15 mkV (p<0.01) in
standing at ease, and to 19.96+/2D11.01 mkV (p<0.01) when subjects
stood on tip toes. Lateral head bending in subjects, standing at ease
and feeling extremely cold increased the EMG 402D60% (p<0.01) in
the contralateral DM without any significant effect on the
ipsilateral DM. The results suggest that in man TMT is influenced by
tonic postural reflexes.
Received 25 August 1994; accepted in final form 21 November 1995.
APS Manuscript Number A900-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 8 December 95