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. 2011 Nov-Dec;46(6):581–591. doi: 10.4085/1062-6050-46.6.581

Table 4.

Incidence of Decreased Performance and Heat Illness Related to Inadequate Hydration (N = 276)

Item Responseb Groupa
Low Mod High Total
1. Have you ever experienced a major decrease in running performance that you feel was caused from being dehydrated? No, % 36 27 17 27
Once, % 29 26 21 25
More than once, % 33 41 59 44
Do not know, % 2 5 3 4
Mean ± SD 2.0 ± 0.8c 2.1 ± 0.8 2.4 ± 0.8 2.2 ± 0.8
2. Have you ever suffered heat-related illness symptoms (severe muscle or stomach cramping, light-headedness, dizziness, nausea, or loss of ability to think clearly) while running that you feel were caused from being dehydrated? No, % 58 62 45 55
Once, % 21 16 28 22
More than once, % 21 21 26 23
Do not know, % 1 1 0 1
Mean ± SD 1.6 ± 0.8 1.6 ± 0.8 1.8 ± 0.8 1.7 ± 0.8

a Low, Mod, and High are tertile classifications based on training volume, expected performance, and running experience.

b 1, no; 2, once; 3, more than once.

c Different from High (P = .001).