The health and performance of ultra-endurance athletes is dependent on avoidance of performance limiting hypohydration while also avoiding the potentially fatal consequences of exercise-associated hyponatremia due to overhydration. In this work, key factors related to maintaining proper hydration during ultra-endurance activities are discussed. In general, proper hydration need not be complicated and has been well demonstrated to be achieved by simply drinking to thirst and consuming a typical race diet during ultra-endurance events without need for supplemental sodium. As body mass is lost from oxidation of stored fuel, and water supporting the intravascular volume is generated from endogenous fuel oxidation and released with glycogen oxidation, the commonly promoted hydration guidelines of avoiding body mass losses of >2% can result in overhydration during ultra-endurance activities. Thus, some body mass loss should occur during prolonged exercise, and appropriate hydration can be maintained by drinking to the dictates of thirst.
*Department of Veterans Affairs, Northern California Health Care System, Physical Medicine and Rehabilitation Service
†Department of Physical Medicine and Rehabilitation, University of California Davis Medical Center, Sacramento
‡Ultra Sports Science Foundation, El Dorado Hills, CA
This material is the result of work supported with resources and the use of facilities at the VA Northern California Health Care System.
The contents reported here do not represent the views of the Department of Veterans Affairs or the United States Government.
Disclosure: The author declares no conflict of interest.
Reprints: Martin D. Hoffman, MD, Department of Physical Medicine & Rehabilitation (117), Sacramento VA Medical Center, 10535 Hospital Way, Sacramento, CA 95655-1200 (e-mail: firstname.lastname@example.org).