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). | |||||||||
| H | 137.3 | 14.50* | 1991 | 134.8 | 15.02 | 2025 | +34 | 118† | 84/21 |
| L | 137.2 | 14.50 | 1989 | 132.8 | 14.95 | 1985 | −4 | 71 | 76/19 |
| W | 137.5 | 14.50 | 1993 | 131.8 | 14.95 | 1970 | −23 | 0 | 24/6 |