Table 4 Hydration by sodium intake

Runner characteristics, n (%)

42 (29.1)

63 (43.8)

39 (27.1)

Age, years

45 (7.4); 45 (28–63)

42 (8.8); 43 (23–65)

42 (9.5); 43 (26–57)

0.26

 Female, n (%)

16 (38)

16 (25)

12 (31)

0.38

 Male, n (%)

26 (62)

47 (75)

27 (69)

Height, cm

176 (7.7); 173 (164–193)

177 (8.4); 178 (158–189)

175 (9.2); 177 (157–195)

0.53

Weight (starting), kg

73 (13.2); 72 (52–103)

75 (10.9); 74 (55–105)

75 (11.3); 75 (57–107)

0.59

BMI, kg/m²

24 (2.9); 23 (18–31)

24 (2.7); 24 (20–33)

25 (3.3); 24 (19–34)

0.55

Pack weight (starting), kg

9 (2.1); 9 (6–15)

11 (2.8); 10 (7–17)

13 (3.4); 11 (8–16)

< 0.01

 Body weight change, kg

− 10 (7.6); − 10 (− 50–3)

− 2 (0.8); − 2 (− 3–0)

1 (0.7); 1 (0–2)

< 0.01

 Serum sodium, mEq

141 (4.3); 140 (133-153)

142 (6.8); 140 (124–160)

139 (5.4); 139 (126–156)

0.05

Sodium intake rate, mg/h

323 (198.6); 280 (74–860)

329 (264.3); 250 (40–1500)

279 (156.4); 240 (83–768)

0.52

Total sodium ingested, g

4 (2.4); 4 (1–9)

4 (3.5); 4 (1–18)

5 (3.1); 4 (1–14)

0.53

Sodium diagnoses

< 0.01

 Hyponatremia, n (%)

1 (2.4)

1 (1.9)

6 (18.8)

 Hypernatremia, n (%)

8 (19.5)

14 (26.4)

4 (12.5)

 Normonatremia, n (%)

32 (78.1)

38 (71.7)

22 (68.8)

Temperature of races

0.31

 Hot races, n (%)

19 (45.2)

49 (77.8)

24 (60)

 Cold races, n (%)

23 (54.8)

14 (22.2)

14 (40)

Pace, min/km

9 (2.1); 9 (6–14)

11 (2.8); 10 (7–18)

13 (3.4); 13 (6–20)

< 0.01

Total race time, h

12.4 (2.9); 12 (8–20)

14 (3.7); 13 (9–23)

17 (4.3); 18 (8–26)

< 0.01

Finishing rank, n (%)

< 0.01

 Top 10%

8 (20)

9 (14.5)

4 (10)

 11–25%

8 (20)

18 (29)

0

 26–50%

14 (35)

17 (27.4)

6 (15)

 51–75%

7 (17.5)

13 (21)

14 (35)

 > 75%

3 (7.5)

5 (8.1)

16 (40)