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).