High incidence of hyponatremia in trained rowers during a four-week training camp

Results Hyponatremia ([Na] < 135 mmol/L) was observed in 70% of the rowers. The highest incidence amounted to 43% at day 18, when training volume was highest. [Na] decreased from 143 ± 8.7 mmol/L (baseline) to 134.5 ± 5.4 mmol/L (day 18, p< 0.01). Hyponatremia was associated with body mass gain in the preceding 24 hours (p<0.01). [Na] returned to normal values at day 28 (139.8 ± 3.9 mmol/L). Relative fluid intake (L/m body surface area) increased from day 7 (males: 2.79 ± 0.78 L/m; females: 2.20 ± 0.70 L/m) to day 28 (3.88 ± 0.69 L/m and 2.65 ± 0.93 L/m; p<0.05). No athlete developed symptomatic hyponatremia.