Table 2 Predicted percentage body mass loss due to dehydration at end of 42 km marathon held in cool/temperate (18°C) weather for runners of various body mass drinking 400–800 ml/h while running at 8.5–15 km/h.

Body mass (kg)	Fluid intake (ml/h)	8.5 km/h	10 km/h	12.5 km/h	15 km/h
50	400	−0.4	−1.1	−2.0	−2.6
	600	1.6	0.6	−0.6	−1.5
	800	3.6	2.2	0.7	−0.3
70	400	−1.8	−2.3	−3.0	−3.4
	600	−0.4	−1.1	−2.0	−2.6
	800	1.1	0.1	−1.0	−1.8
90	400	−2.6	−3.0	−3.5	−3.9
	600	−1.5	−2.1	−2.8	−3.2
	800	−0.4	−1.1	−2.0	−2.6

Underlined type illustrates overdrinking relative to sweating rate. Bold type illustrates sufficient dehydration to compromise performance.