Table 1

 Sodium balance calculations for three groups of runners running at ∼10 km/h for four hours while ingesting solutions with different [Na+]

Pre-race [Na+] (mmol/l) (A)Pre-race ECF volume (litres) (B)Pre-race ECF Na+ content (mmol) (A×B)Post-race [Na+] (mmol/l) (C)Post-race ECF volume (litres) (D)Post-race ECF Na+ content (mmol) (C×D)Post-race Na+ balance (mmol) (E) (C×D)−(A×B)Amount of Na+ ingested (mmol) (F)Apparent amount (mmol)/rate of Na+ loss during exercise (mmol/h) ((F−E)/4)
H, High sodium intake; L, low sodium intake; W, water during exercise.
*Based on 25% of mean body weight of 57.7 kg for the total group of runners. Weights for different groups were not reported.
†From table 2 of Twerenbold et al1: to convert mg sodium (table 2) into mmol sodium, divide by the molecular weight of sodium (22.99).