Table 3 Predicted percentage body mass loss due to dehydration at the end of a 42 km marathon held in warm (28°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	−1.2	−1.9	−2.6	−3.2
	600	0.8	−0.2	−1.3	−2.0
	800	2.7	1.5	0.1	−0.9
70	400	−2.5	−2.9	−3.5	−3.9
	600	−1.0	−1.7	−2.5	−3.1
	800	0.4	−0.5	−1.6	−2.3
90	400	−3.1	−3.5	−4.0	−4.3
	600	−2.0	−2.6	−3.2	−3.6
	800	−0.9	−1.7	−2.5	−3.0

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