Table 4.
Factors that influence exertional hyponatremia. Letters in column 1 refer to the symbols embedded in Figure 2.
| Symbols in Figure 2 | Men | Women | Scenario (Ambient Temperature, °C) | Final Serum Na+ (mmol/L) | Body Mass Change (%) | Exercise Duration (h) | Rate of Fluid Intake (ml/h) | Mean Initial Body Mass (kg) | Source |
|---|---|---|---|---|---|---|---|---|---|
| Background data points | a | a | 11 endurance events a | See Figure 3 | See Figure 3 | b | b | b | [20] |
| A | 42 | 164 km cycling (34.4) | 141 | −0.8 | 9.1 | 649 | 85.9 | [55] | |
| B | 31 | 164 km cycling (24.4–39.5) | 141 | −1.4 | 9.0 | 700 | 85.4 | [66] | |
| C | 6 | 164 km cycling (34.4) | 140 | −0.1 | 9.0 | 520 | 67.3 | [55] | |
| D | 50 | 100 km run (15.6–21.7) | 138 | −2.6 | 12.2 | 600 | 74.9 | [71] | |
| E | 7 | Treadmill walk (41.0) c | 136 | −0.1 | 4.0 c | 640 | 77.9 | [61] | |
| F | 5 | 44 km trail run (15–34) | 131 | −2.2 | 9.3 | 290 d | 81.9 | [72] | |
| G | 1 | Ironman triathlon (21.0) e,f |
131 | +0.9 | 13.3 | 733 | 57.5 | [73] | |
| H | 1 | 164 km cycling (24.4–39.5) g | 130 | +4.3 | 8.9 | 1,500 | 72.0 | [66] | |
| I | 1 | Ironman triathlon (21.0) e,f |
130 | +2.5 | 12.0 | 764 | 59.0 | [73] | |
| J | 1 | 164 km cycling (24.4–39.5) g | 130 | +0.1 | 10.6 | 1,400 | 77.5 | [66] | |
| K | 2 | 5 | Ironman triathlon e | 128 | −0.5 | 12.3 | b | 62.5 | [74] |
| L | 1 | Treadmill walk (41.0) c | 122 | +4.0 | 4.0 c | 2,061 h | 82.2 | [61] | |
| M | 1 | Ironman triathlon e | 116 | +5.0 | 14.0 | 1,642 | b | [75] |
Note: values are means or medians (columns 5–9) when the number of subjects is ≥ 2. a, 3 Ironman triathlons, 6 marathon footraces (42.2 km), a 109 km cycling tour, and a 160 km footrace (2,135 athletes); b, not reported; c, 5.6 km/h, 5% grade, 30 min walking and 30 min seated rest per hour; d, runners were allowed to drink and eat only fluids and food provided by the race organizing committee, at 11 intermediate checkpoint stations, positioned every 3–5 km; they did not drink when thirsty or ad libitum; e, triathlon stages were 3.8 km swim, 180 km cycle, 42.2 km run; f, this athlete stopped during the cycling stage due to hyponatremic illness; g, identical to cyclists LC and AM in Table 4 (column 1); h, this individual purposefully overhydrated.