Fig. 1.

A: increase in serum osmolality from baseline over dehydration (%body wt loss) via exercise in the heat was significantly affected by group (P = 0.034) with attenuated rise observed for cystic fibrosis (CF) subjects [sweat Na⁺ concentration ([Na⁺]) = 132.6 ± 6.4 mmol/l] compared with Controls (mean ± SD sweat [Na⁺] = 43.7 ± 9.9 mmol/l) and non-CF salty sweaters (SS, [Na⁺] = 91.0 ± 17.3 mmol/l). B: scatter plot indicating relationship (r = −0.76, P < 0.001) between individual subjects' change from baseline in serum osmolality observed at 3% dehydration and regional sweat [Na⁺]. *Less than Control, P < 0.05.