Whittlesey, M. J., Armstrong, L. E., Maresh, C. M., Elliott, T. A., Casa, D. J., & Kavouras, S. A. (1998). The effects of hypohyration on running economy in a mild (23 degrees Celsius) environment. Medicine and Science in Sports and Exercise, 30(5), Supplement abstract 1624.

Whether hydration level had an effect on running economy during strenuous exercise was evaluated. Collegiate distance runners (N = 10) performed two 10-minute euhydrated and two 10-minute hypohydrated (-5% BW) trials at treadmill speeds that evoked 70% and 85% VO2max.

Rectal temperature was significantly higher when Ss were dehydrated but the change in temperature during the exercises was significantly less than in the euhydrated condition. Cardiac output was significantly less during the dehydration trial. There was no difference in oxygen consumption between trials.

Implication. Body water loss of more than 5% body weight did not alter the running economy of highly trained distance runners in a mild environment despite differences in some physiological measures.

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