The purpose of this study was to investigate selected physiological adaptations to heat and humidity training in elite athletes. Ten well trained middle distance runners were exposed to the warm humid conditions of Atlanta(average a.m. temperatures (T) and relative humidity (RH) = 21 ± 2.8°C, 78 ± 6.1 percent; average p.m. T and RH = 28 ± 3.0° C, 56 ± 1.9 percent) for a period of eighteen days. Two days prior to leaving Australia and two days post return subjects completed a treadmill test conducted in an environmental chamber set at a T of 30° C and a RH of 50 percent. Earlobe blood samples were drawn prior to the commencement of the test and immediately on completion of the exercise intervals and analyzed for La. Body fluid loss was estimated by changes in dry nude body weight. Pre-Atlanta and post-Atlanta blood samples were drawn from the antecubital vein and analyzed for hematocrit, RBC volume and RBC creatine. Blood variables monitored in Atlanta on the 2nd, 7th, 13th, and 18th day of training included: RBC volume, hemoglobin, hematocrit, and the hormones, aldosterone and ADH. Although individual differences were observed, there was no significant difference (p >.05) in RBC volume, hemoglobin, hematocrit, aldosterone, or ADH for their stay in Atlanta. For the heat test in Australia, there was some evidence for exercise HR to be lower (176 ± 11.8 vs 173± 11.1, p <.05) post- Atlanta, along with decreased blood La (2.8± 2.2 vs 1.9 ± 1.2, p <.05). Additionally, a 40% decrease in body fluid loss, based on nude body weight, was estimated post-Atlanta (1.1± 0.4 vs 0.7 ± 0.2, p <.05). An increase in RBC creatine concentration (66 ± 18.3 vs. 74 ± 14.5, p <.05) suggested training in the heat was responsible for producing a younger population of RBC. Due to a more efficient release of O2, a younger population of RBC could be an important factor for performance.
G-16 POSTER PHYSIO FUNCT: TRAINED ATHLETES