Division of Gastroenterology, Hepatology and Nutrition, Department of Pediatrics, Children's Hospital of Philadelphia, 3535 Market Street, Room 1556, Philadelphia, PA 19104, USA.
Eur J Appl Physiol. 2010 Mar;108(4):779-89. doi: 10.1007/s00421-009-1290-4.
Environmental limits for uncompensable heat stress, above which an imbalance between heat gain and heat loss forces body core temperature upward (i.e., the upper limits of the prescriptive zone), are unknown for children. To determine these limits, 7 lean and 7 obese 9- to 12-year-old heat-acclimated boys performed four randomized trials each on separate days to determine the critical water vapor pressure (P (crit)) forcing an upward inflection of body core temperature at several ambient temperatures. Subjects walked continuously on a treadmill at 30% maximal aerobic capacity at a constant dry bulb temperature (T (db) = 34, 36, 38 or 42 degrees C). After a 30-min equilibration period at 9 torr, ambient water vapor pressure increased approximately 1 torr every 5-min until a distinct breakpoint in the core temperature versus time curve was evident. Compared to the lean subjects, obese subjects had significantly lower environmental limits (P < 0.03) in warm environments (P (crit), for lean vs. obese, respectively = 32.9 +/- 0.7 vs. 30.3 +/- 0.8 torr at T (db) = 34 degrees C; 29.6 +/- 0.6 vs. 27.2 +/- 0.9 torr at T (db) = 36 degrees C; 27.8 +/- 0.6 vs. 24.7 +/- 0.9 torr at T (db) = 38 degrees C; 25.5 +/- 0.7 vs. 24.5 +/- 1.5 torr at T (db) = 42 degrees C). These results suggest that separate critical environmental guidelines should be tailored to lean and obese children exercising in the heat.
环境限制不可补偿的热应激，在这之上，热量获得和热量损失之间的失衡迫使身体核心温度上升（即，规定区域的上限），对于儿童来说是未知的。为了确定这些限制，7 名瘦和 7 名肥胖的 9 至 12 岁热适应男孩在不同的日子里分别进行了四次随机试验，以确定临界水蒸气压力（P（crit）），该压力迫使身体核心温度在几个环境温度下向上弯曲。受试者在恒定干球温度（T（db）= 34、36、38 或 42°C）下以 30%最大有氧能力连续在跑步机上行走。在 9 托环境下平衡 30 分钟后，环境水蒸气压力大约每 5 分钟增加 1 托，直到核心温度与时间曲线出现明显的转折点。与瘦受试者相比，肥胖受试者在温暖环境中的环境限制（P < 0.03）明显较低（P（crit），分别为 32.9 +/- 0.7 对 30.3 +/- 0.8 托，T（db）= 34°C；29.6 +/- 0.6 对 27.2 +/- 0.9 托，T（db）= 36°C；27.8 +/- 0.6 对 24.7 +/- 0.9 托，T（db）= 38°C；25.5 +/- 0.7 对 24.5 +/- 1.5 托，T（db）= 42°C）。这些结果表明，在热环境中运动的瘦胖儿童应分别采用单独的临界环境指南。
