Table 3.
Hydration markers
| Parameter | 31°C |
34°C |
Mixed-Effects Model |
||||||
|---|---|---|---|---|---|---|---|---|---|
| Pre | 4 h | 8 h | Pre | 4 h | 8 h | Time effect | Condition effect | Interaction | |
| ΔBody mass, % | 0.0 (0.0) | −0.6 (0.3)* | −1.4 (0.4)*† | 0.0 (0.0) | −0.8 (0.6)* | −1.9 (0.5)*‡† | <0.001 | 0.02 | 0.008 |
| Blood samples | |||||||||
| Subjects, n | 15 | 15 | 15 | 15 | 15 | 15 | |||
| ΔPlasma volume, % | 0.0 (0.0) | −3 (7) | −4 (6) | 0.0 (0.0) | −9 (8)* | −9 (5)* | <0.001 | 0.01 | 0.02 |
| Plasma osmolality, mosmol/kgH2O | 285 (4) | 283 (2) | 284 (2) | 284 (4) | 284 (3) | 285 (3) | 0.28 | 0.95 | 0.23 |
| Serum sodium, mmol/L | 142 (3) | 143 (2)* | 145 (2)* | 143 (2) | 144 (3) | 145 (2)*‡ | <0.001 | 0.32 | 0.49 |
| Serum potassium, mmol/L | 4.1 (0.3) | 4.2 (0.3) | 4.2 (0.3) | 4.1 (0.2) | 4.2 (0.2) | 4.2 (0.3) | 0.21 | 0.77 | 0.91 |
| Serum uric acid, mg/dL | 5.6 (2.2) | 5.1 (1.1) | 4.9 (0.7) | 4.8 (0.9) | 5.0 (0.9) | 4.8 (0.8) | 0.27 | 0.20 | 0.21 |
| Urine samples | |||||||||
| Subjects, n | 15 | 15 | 14 | 15 | 14 | 13 | |||
| Urine specific gravity | 1.010 (0.007) | 1.016 (0.006) | 1.023 (0.004)*‡ | 1.009 (0.006) | 1.016 (0.007)* | 1.032 (0.018)*‡ | <0.001 | 0.11 | 0.10 |
| Urine osmolality, mosmol/kgH2O | 450 (312) | 666 (207)* | 929 (121)*‡ | 366 (315) | 666 (242)* | 959 (129)*‡ | <0.001 | 0.55 | 0.11 |
| Urine sodium, mmol/L | 51 (49) | 76 (50) | 108 (60)*‡ | 39 (48) | 62 (37) | 49 (36)† | 0.02 | 0.02 | 0.005 |
| Urine potassium, mmol/L | 30.9 (20.9) | 57.4 (25.1)* | 98.3 (32.1)*‡ | 21.9 (20.5) | 57.8 (30.2)* | 120.1 (39.5)*‡ | <0.001 | 0.46 | 0.01 |
| Urine uric acid, mg/dL | 3.8 (3.3) | 1.1 (0.4)* | 0.6 (0.3)* | 3.7 (3.5) | 0.8 (0.5)* | 0.3 (0.2)*‡ | <0.001 | 0.96 | 0.28 |
Values are presented as mean (SD). Hydration markers were measured from blood and urine samples collected at preexposure (Pre) and 4 h and 8 h into each exposure. Data were analyzed with a repeated-measures linear mixed model (time × trial), and exact P values are reported. If a significant interaction or main effect was found, post hoc analyses were completed with Šídák’s multiple comparisons tests. *Different from Pre (P < 0.05); ‡different from 4 h (P < 0.05); †different from 31°C (P < 0.05).