The present study examined the hemodynamics underlying blood
pressure elevations for evidence of a shift in the control of
blood pressure during prolonged mental stress. Mean arterial
pressure (MAP), cardiac output (CO), and total peripheral
resistance (TPR) were measured at rest, during a 28-min mental
arithmetic stress task, and during recovery, in 30 young healthy
men and women. The stress task elicited a sustained increase
in MAP: CO rose during the first half of the task but returned
to baseline levels during the last quarter of the task, whereas
TPR increased as the task progressed. When participants'
hemodynamic reactions were classified as cardiac, vascular,
or neither, there were more cardiac reactors early relative
to late in the task, whereas there were more vascular reactors
late relative to early. Thus, the sustained pressor response
was initially supported mainly by cardiac mechanisms but
subsequently by predominantly vascular mechanisms.