Proper Hydration: Running Low on Water?

Any time a person goes for a run, their hydration level will impact how that person feels and the performance of that run.  The body cools itself during a run by the evaporation of sweat from the skin’s surface.  The fluid lost during exercise needs to be replenished so that the body can function as its’ very best.  Some people are told to drink as much fluid they can so that they won’t be dehydrated, while others are told to limit drinking so that they don’t become over-hydrated.  

Dehydration is caused by the loss of fluids from sweat, urine, and respiratory losses, or when fluid intake does not match up to fluid losses.  Since the body is approximately 65% water, a significant decrease in body water stores will alter normal physiological function.1.  Dehydration can occur while working out in a warm/hot climate due to the body’s increased sweat rate.  People with already high sweat rates are at greater risk for dehydration.  Multiple runs, not eating, and/or drinking enough fluids may also contribute to dehydration among other things.

Dehydration can lead to heat illness.  The basic signs and symptoms of heat illness caused by dehydration can be irritability, headache, dizziness, cramps, chills, vomiting, nausea, head or neck heat sensations, and decreased performance.2.  So how can one reduce the risk of having heat illness? Runners can start by beginning all runs properly hydrated by consuming 17 to 20 fl. oz. of water/sports drink 2 to 3 hours before exercise and 10 to 12 fl. oz. of water/sports drink about 15 minutes before exercise.  Rehydration should be focused on replenishing any fluid loss accumulated during the run.  Drinking fluid around 50℉ to 59℉ will absorb faster and is recommended post-run.

In addition to being properly hydrated, a runner can help reduce the risk of heat illness by being educated on appropriate fluid replacement, monitoring body weight when possible, monitoring urine color (see chart below), taking time to become acclimated to the environment and not running in the heat of the day if possible.

1. Oppliger, R., & Bartok, C. (2002). Hydration Testing Of Athletes. Sports Medicine, 32(15), 959-971.

2. Casa, D. J., L. E. Armstrong, S. K. Hillman, S. J. Montain, R. V. Reiff, B. S. E. Rich, W. O. Roberts, J. A. Stone. National Athletic Trainers’ Association Position Statement. Fluid replacement for athletes. J. Athletic Training. 35 (2): 212–224, 2000.