TABLE 1.

Hydration status and body temperature at rest and during prolonged exercise in the heat

	Exercise time (min)
	Rest	30	60	90	118 ± 1
Body mass, kg
Progressive dehydration	70.4 ± 3.5	—	—	—	67.6 ± 3.5 †
Euhydration control	70.1 ± 3.6	—	—	—	69.7 ± 3.5
Body mass change, %
Progressive dehydration	0	—	—	—	−4.0 ± 0.2 †
Euhydration control	0	—	—	—	−0.6 ± 0.1
Red cell volume, L
Progressive dehydration	1.85 ± 0.1	1.79 ± 0.1	1.79 ± 0.1	1.75 ± 0.1 †	1.74 ± 0.1 †
Euhydration control	1.85 ± 0.1	1.83 ± 0.1	1.80 ± 0.1	1.83 ± 0.1	1.82 ± 0.1
Plasma volume, L
Progressive dehydration	3.12 ± 0.1	2.64 ± 0.1	2.58 ± 0.1 †	2.48 ± 0.1*, †	2.42 ± 0.1*, †
Euhydration control	3.11 ± 0.1	2.74 ± 0.1	2.71 ± 0.1	2.75 ± 0.1	2.75 ± 0.1
Rectal temperature, °C
Progressive dehydration	36.9 ± 0.1	37.8 ± 0.1	38.2 ± 0.05*	38.6 ± 0.1*, †	38.9 ± 0.1*, †
Euhydration control	36.8 ± 0.1	37.8 ± 0.1	38.1 ± 0.05*	38.2 ± 0.05*	38.3 ± 0.1*
Mean skin temperature, °C
Progressive dehydration	35.9 ± 0.1	36.2 ± 0.2	36.1 ± 0.2	36.3 ± 0.2	36.3 ± 0.2
Euhydration control	35.7 ± 0.1	36.3 ± 0.2	36.1 ± 0.2	36.0 ± 0.2	36.1 ± 0.3

Values are means ± SEM. For body mass and rectal and mean skin temperatures, n = 8 subjects; for red cell and plasma volumes, n = 7 subjects.

^* P < .05 versus 30 min.

^† P < .05 versus euhydration control.