| Popis: |
Lower body negative pressure (LBNP) sequesters blood from the thorax into dependent regions of the pelvis and legs, effectively decreasing central blood volume. Cold exposure will alter central blood volume in response to variations in core and skin temperature. This may lead to improved tolerance of LBNP. The purpose of this study is to determine the effects of cold exposure and lower body negative pressure on cardiovascular and thermoregulatory variables. Eleven males (20.3 ± 2.7) underwent two 20-minute exposures to LBNP (AMB and COLD). During one trial the subjects were exposed to cold air (10°C) the other they were exposed to ambient temperature (23°C). The trials consisted of a 100-minute pre-LBNP period followed by a 20-minute exposure to LBNP and then a 15-minute recovery period. Cardiovascular variables were recorded every 30 minutes using bioimpedance. Rectal temperature and skin temperatures were recorded every 15 minutes and thermal sensation was assessed every 15 minutes using the Gagge and Modified Gagge scales. A repeated measures ANOVA demonstrated a significant condition x time interaction for rectal temperature (Tre) (p = 0.002), mean skin temperature (p < 0.05), thermal sensation (p = 0.002), modified thermal sensation (p < 0.05) and tissue insulation (p < 0.05). There was also a significant condition x time interaction for mean arterial pressure (p = 0.014), and cerebral oxygenation (p = 0.034). From these data, it may be suggested that cold alters the physiological response to LBNP. |
