Runners: Drink to Your Health

By Aravind Athiviraham, MD, FRCS(C), Assistant Professor of Orthopaedic Surgery

Beware your thirst.

That’s the most important rule in sports. If you are thirsty, hydrate.

Every time you break a sweat, you siphon off fluids that help regulate your metabolism. Replenish every drop – especially in muggy August – for optimal health and performance. Rehydration is key to maintaining your mental focus, muscle function and cardiovascular system.

Even seasoned runners are vulnerable to dehydration in hot weather. Think of the Chicago Marathon in 2007, when temperatures climbed into the upper 80s. Nearly 50 runners were hospitalized. Hundreds were treated at first aid stations.

The clinical definition of dehydration is when lost fluids exceed the amount taken in, leading to an imbalance. The adult human body is about 60 percent of water. If you lose more than 2 percent of your weight, you’re dehydrated. If you lose 5 percent, you’re in danger and 10 percent is catastrophic.

Classic signs of dehydration include:

  • Dry mouth
  • Edema, or warm, swollen skin
  • Irritability
  • Confusion
  • Muscle cramps
  • Heart palpitations
  • Dark, concentrated urine


Heat exhaustion occurs when your body temperature rises above 98.6 F but below 104 degrees F. Athletes who recover will probably be OK.

Heat stroke – which strikes when your body temperature exceeds 104 degrees F – is rarer and more dangerous. You can suffer organ failure, coma and even death.

Runners are savvy about hydration, but sometimes too savvy. They over-hydrate, which can lead to hyponatremia. You retain excess water, which dilutes sodium, the electrolyte responsible for blood pressure. Your temperature is normal, but your mental state changes. You may be confused, weak or nauseous.

A rule of thumb: Hydrate with water for periods of exercise under an hour. For longer periods of activity, drink beverages like Gatorade or Powerade, which replenish carbs and electrolytes. Hydrate before, after and during activity.

If the race is under four hours, drink 10 to 12 ounces every 20 minutes. It works out to 30 to 36 ounces an hour.

If it’s a four- to five-hour race, you're looking at 8 ounces every 20 minutes, or 24 ounces an hour. Over five hours, drink four to six ounces every 20 minutes, or 12 to 18 ounces an hour. You reduce the amount to lower the risk of  hyponatremia.

When I was a sports fellow, I was involved in covering several football teams. Football carries a risk of heat exertion 11 times high than other majors sports combined. The players, who are wearing heavy equipment, are so focused on the game that they don’t rehydrate as often as they should. The coach is also telling you, “Go, go, go! ’’

They have Gatorade on the sidelines. But they also start IVs in the locker rooms.  Some players would pour water on their heads. Sure, it feels good and cools you down. But I recommend replenishing your thirst first.

Aravind Athiviraham, MD, FRCS(C), is an Assistant Professor of Orthopaedic Surgery at the University of Chicago Medicine. The orthopedic sports medicine specialist has supervised athletic events ranging from youth soccer games to NFL training camps.


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