| Female reproductive hormones, aging, global heating and local heating are factors affecting skin blood flow (SBF), but their effect on electrical stimulation (ES) has never been examined until the present investigation. To investigate female reproductive hormones, nine women (age= 25.6+/-3.5 years) with a normal menstrual cycle (MC) underwent ES in thermoneutral (25°+/-0.5°C) and warm environments (35°+/-0.5°C). To investigate aging, ES was applied on active young (n=15, age= 32.1+/-8.3 years) and old (n=8, 64.5+/-6.2 years) groups in thermoneutral and warm environments. To investigate the effect of global and local heating, groups of 15 and 18 subjects (age=18--40 years) experienced ES under global and local heating, respectively. During global heating ES was applied in thermoneutral (25°+/-0.5°C) and warm environments (35°+/-0.5°C), and during local heating, skin temperature was elevated to 25°C, 35°C, and 40°C. The SBF was measured by Laser Doppler Imager for periods of 15 minutes pre, during, and post ES. Sweat rate and skin temperature were monitored at the forehead, chest, ipsilateral and contralateral thighs. Tympanic temperature was taken every 5 minutes. In all of these experiments, ES did not increase SBF in the thermoneutral environment, but in the warm environment, the SBFs were significantly increased during and post ES compared to pre ES. In the warm environment, the SBF was significantly higher during the follicular phase at baseline (P=0.02), whereas, no significant differences were found during and post ES due to the higher SBF response to ES during the luteal phase (P>0.5). In the active young and old groups, no significant difference in SBF was caused by ES (P=0.50). Comparing local heating 35°C to global heating, the SBF response to ES was not significantly different. The SBF, however, was significantly higher at 40°C local heating of the skin compared to global heating or to 35°C of local heating. The response of SBF to ES was modulated by female reproductive hormones. Aging had no effect on the SBF response to ES due the high physical activities of the old group. Local heating of the skin to 30°--40°C caused the same or better SBF response to ES than global heating, which suggests that the combined effect of ES and local heating may be an effective method to increase wound healing. |
