title: Sodium supplementation has no effect on endurance performance during a cycling time-trial in cool conditions: a randomised cross-over trial.
abstract: BACKGROUND
  Sodium ingestion during exercise may exert beneficial effects on endurance performance by either its ability to attenuate the decrease in plasma volume or reduce the risk of Exercise Associated Hyponatremia (EAH). This study aimed to investigate the effect of sodium supplements on endurance performance during a 72 km road cycling time-trial in cool conditions (13.8 ± 2.0°C).
  
  
  METHODS
  Nine well-trained cyclists (5 male, 4 female) participated in this randomized, double-blinded cross-over study, receiving either a 700 mg(.)h(-1) salt capsule, or a corn flour placebo during the time trial. Water was ingested ad-libitum throughout the time trial. Measurements were taken pre, post, and 40 min following time-trials, analysing blood, sweat, and urinary hydration and sodium concentration.
  
  
  RESULTS
  Sodium supplements had no effect on time-trial performance (overall time = 171 min sodium vs. 172 min placebo; p = 0.46). There was also no effect on the change in plasma sodium concentration from pre to post time trial between trials (relative plasma [Na(+)] change (pre-post): sodium = 0.56%, placebo = 0.47%; p = 0.60). The greatest difference observed was a significantly change in plasma volume from pre to post exercise between the salt and the placebo trial (p = 0.02), which corresponded with an increased thirst with sodium supplementation.
  
  
  CONCLUSIONS
  Sodium supplements therefore do not improving performance during exercise of approximately 3 h duration in cool conditions.
authors.affiliation: Department of Human Nutrition, University of Otago, P.O. Box 56, Dunedin, Otago 9054, New Zealand.
authors.forename: Samuel David
authors.initials: SD
authors.lastname: Cosgrove
authors.affiliation: Department of Human Nutrition, University of Otago, P.O. Box 56, Dunedin, Otago 9054, New Zealand.
authors.forename: Katherine Elizabeth
authors.initials: KE
authors.lastname: Black
keywords: Endurance exercise; Fluid balance; Hydration; Hyponatremia; Salt; Sodium; Thirst