Handgrip contraction induces a linear increase in arterial pressure by peripheral vasoconstriction, increased heart rate and a decrease in stroke volume.
OBJECTIVE
The hypothesis that isometric handgrip induces a progressive increase in arterial pressure and a linear increase in setpoint for arterial pressure control was tested.


METHODS
The continuous time course of changes in heart rate (HR), stroke volume (SV) and mean arterial pressure (MAP) was recorded during a 2-min handgrip contraction of 40% of maximal voluntary contraction force. Twice during the development of the handgrip-induced, gradual pressure increase of ∼25 mmHg, additional, transient changes in arterial pressure were mechanically induced. The subsequent baroreflex responses to these additional pressure changes were studied. The additional steep increase in arterial pressure (∼10 mmHg) was induced both after 70 and 100 s of handgrip contraction, by inflating bilateral thigh cuffs to suprasystolic pressure. Cuff pressure was released after 10s, thus introducing a steep decrease in MAP.


RESULTS
During the development of the handgrip-induced pressure increase, HR increased, SV decreased, cardiac output (CO) increased slightly and total peripheral conductance (TPC=CO/MAP) increased (i.e. peripheral vasoconstriction). The circulatory responses to the additional, sudden increase and subsequent decrease in arterial pressure after 70 and 100 s perfectly adjusted arterial pressure back to the linear increase in MAP, indicating an effective baroreflex response.


CONCLUSIONS
The increase in MAP which characterizes handgrip-induced pressure response can be regarded as a result of a gradual increase in the set point of the arterial baroreflexes, with no change in the time course and magnitude of the baroreflex responses to additional, induced changes in MAP.
Toska
K
K
Department of Physiology, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway. ktoska@medisin.uio.no
D000222:Adaptation, Physiological; D017704:Baroreflex; D001794:Blood Pressure; D005260:Female; D018737:Hand Strength; D006339:Heart Rate; D006801:Humans; D007537:Isometric Contraction; D016014:Linear Models; D008297:Male; D008955:Models, Cardiovascular; D018482:Muscle, Skeletal / Q000502:physiology*; D013318:Stroke Volume; D013997:Time Factors; D014655:Vascular Resistance; D014661:Vasoconstriction; D055815:Young Adult