Development of Hyponatremia in highly trained rowers during a 32-day training camp
Purpose: The aim of this study was to determine the incidence of hyponatremia during a training camp consisting of high volume training and its relationship to fluid intake, urine volume and arginine vasopressin (AVP) secretion as assessed by measurements of plasma copeptin (COP). Methods: 30 members (21 males, 9 females) of the German junior rowing team were studied during the training camp preceding the world championships. Samples for serum sodium ([Na+]), COP, serum osmolality [Osm] and hematocrit (Hct) were taken at baseline before entering the training camp (day 0) and at day 7, day 13, day 18, day 24, and day 28, respectively. In addition, daily absolute fluid intake (AFI) and fluid intake per body surface area (RFI) as well as urine output (UV) and training volume was assessed. Results: A high incidence of hyponatremia was observed (with 43 % of the rowers being hyponatremic at day 18, when training volume was highest). Mean [Na+] decreased from 144 ± 8.7mmol/l (day0) to 134.5 ± 5.4 mmol (day18). [Na+] returned to normal values at day 28 (139.8 ±3.9 mmol). [Osm] also decreased (day 18: 278.8 ± 8.6 mosm/kg). COP decreased from baseline (males: 6.74 ± 2.78 pmol/l; females: 4.78 ± 1.05 pmol/l) to day 28 (3.56 ± 1.70 pmol/l; 3.21 ±1.50 pmol/l) (p<0.05;p<0.05), whereas RFI increased from day 7 (males: 2.79 ± 0.78 l/m2; females: 2.20 ± 0.70 l/m2) to day 28 (3.88 ± 0.69 l/m2 and 2.65 ±0.93 l/m2), respectively (p<0.05). Urine volume (UV) increased simultaneously in male and female athletes, while the difference between AFI and UV (FB) came to a significant low at day 24. None of the athletes developed symptomatic hyponatremia. Conclusion: High volume rowing training frequently leads to hyponatremia despite decreasing copeptin levels. Overdrinking combined with inadequate suppression of AVP may in part explain these findings. However, additional mechanisms probably contribute to the development of hyponatremia under these conditions.
Subject HeadingsHyponatriämie [GND]
Sports; Physiology [MeSH]