Vascular responses in glabrous and nonglabrous skin during acute mental stress in physically trained humans.
Acute mental stress induces sympathetic activation and influences vasomotor control in various organs. In the present study, to better understand the effect of physical training on peripheral vasomotor control during acute mental stress, we compared the skin vascular responses to mental arithmetic (MA) in physically trained and untrained humans. Eight physically trained (T group) and eight untrained (UT group) healthy volunteers performed 2 min of MA aloud in the supine position under a thermoneutral condition (28 degrees C). Skin blood flow (laser-Doppler flowmetry) and local temperature were monitored at the glabrous (palm, sole) and nonglabrous (forearm, calf) sites. Cutaneous vascular conductance (CVC) was evaluated from the ratio of blood flow to mean arterial pressure (tonometry). Local sweating rate (SR) was measured in the sole and calf by the ventilated capsule method. In the T group, the CVC at glabrous sites consistently decreased (P < 0.05) during MA, while in the UT group, the stress-induced decreases in CVC were transient and gradually recovered during MA. The patterns of changes in CVC at the nonglabrous sites were substantially similar to those at the glabrous sites, but the decreases in CVC at the nonglabrous sites were smaller (P < 0.05) than those at the glabrous sites in both groups. Local temperature at the glabrous sites (especially in the sole) showed higher (P < 0.05) values in the T group compared with the UT group. The SR in the sole and calf were increased (P < 0.05) during MA but did not differ between the two groups. These findings suggest that physical training acts to heighten skin temperature at the glabrous sites but not at the nonglabrous sites. It is also suggested that the change of skin temperature by physical training modifies sympathetic vasomotor control in glabrous and nonglabrous skin during acute mental stress in the peripheral level.