title: Sweat sodium loss influences serum sodium concentration in a marathon.
abstract: The aim of this investigation was to determine the influence of sweat electrolyte concentration on body water and electrolyte homeostasis during a marathon. Fifty-one runners completed a marathon race in a warm and dry environment (24.4 ± 3.6 °C). Runners were classified as low-salt sweaters (n = 21; <30 mmol/L of sweat Na+concentration), typical sweaters (n = 20; ≥30 and <60 mmol/L of sweat Na+concentration), and salty sweaters (n = 10; ≥60 mmol/L of sweat Na+concentration). Before and after the race, body mass and a sample of venous blood were obtained. During the race, sweat samples were collected by using sweat patches, and fluid and electrolyte intake were recorded by using self-reported questionnaires. Low-salt, typical and salty sweaters presented similar sweat rates (0.93 ± 0.2, 0.92 ± 0.29, 0.99 ± 0.21 L/h, respectively), body mass changes (-3.0 ± 1.0, -3.3 ± 1.0, -3.2 ± 0.8%), total Na+intake (12.7 ± 8.1, 11.5 ± 9.7, 14.5 ± 16.6 mmol), and fluid intake (1.3 ± 0.8, 1.2 ± 0.8, 1.2 ± 0.6 L) during the race. However, salty sweaters presented lower post-race serum Na+concentration (140.8 ± 1.3 vs 142.5 ± 1.1, 142.4 ± 1.4 mmol/L; P < 0.01) and serum osmolality (297 ± 6 vs 299 ± 5, 301 ± 6 mOsm/kg; P < 0.05) than low-salt and typical sweaters. Sweat electrolyte concentration could influence post-race serum electrolyte concentration in the marathon. However, even the saltiest sweaters did not develop exercise-associated hyponatremia or associated symptoms.
authors.affiliation: Exercise Physiology Laboratory, Sport Science Institute, Camilo José Cela University, Madrid, Spain.
authors.forename: B
authors.initials: B
authors.lastname: Lara
authors.affiliation: Exercise Physiology Laboratory, Sport Science Institute, Camilo José Cela University, Madrid, Spain.
authors.forename: J J
authors.identifier: http://orcid.org/0000-0003-4153-5100
authors.initials: JJ
authors.lastname: Salinero
authors.affiliation: Exercise Physiology Laboratory, Sport Science Institute, Camilo José Cela University, Madrid, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Areces
authors.affiliation: Exercise Physiology Laboratory, Sport Science Institute, Camilo José Cela University, Madrid, Spain.
authors.forename: D
authors.initials: D
authors.lastname: Ruiz-Vicente
authors.affiliation: Exercise Physiology Laboratory, Sport Science Institute, Camilo José Cela University, Madrid, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Gallo-Salazar
authors.affiliation: Exercise Physiology Laboratory, Sport Science Institute, Camilo José Cela University, Madrid, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Abián-Vicén
authors.affiliation: Exercise Physiology Laboratory, Sport Science Institute, Camilo José Cela University, Madrid, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Del Coso
mesh_terms: D000328:Adult; D056352:Athletes; D001834:Body Water; D004326:Drinking; D006801:Humans; D007010:Hyponatremia; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D012420:Running / Q000502:physiology*; D012964:Sodium / Q000097:blood* / Q000378:metabolism; D013542:Sweat / Q000737:chemistry; D013546:Sweating / Q000502:physiology*; D014882:Water-Electrolyte Balance
chemical_list: D012964:Sodium
keywords: athletes; dehydration; fluid balance; hyponatremia; osmolality