How to keep hydrated while exercising in summer heat

Building a tolerance to heat
The ability to tolerate heat varies greatly between individuals. You can improve your capacity to withstand heat stress by repeated and slowly increasing exposures to heat over a period of ten days to two weeks. This process, called acclimatization, may take even longer in people who are less physically fit, children, elderly and those with chronic medical conditions or those using certain medications.

Keep hydrated
Dehydration, which results from the failure to replace fluids lost during activity, can increase the risk for exertional heat illness and stress the cardiovascular system. Experts recommend that to prevent dehydration and heat illness, water lost due to sweating should be replaced at a rate close to or equal to the amount of sweat lost.
For physically active adults, this can range from 3-10 liters per day.

It’s about more than thirst
Relying on thirst alone to determine fluid needs is inadequate. We experience the sensation of thirst only after our bodies are already experiencing the stress of fluid loss. In addition, drinking water extinguishes the sensation of thirst before restoration of fluid balance has occurred. Interspersing sports drinks, which contain sodium, with water during hydration actually helps maintain your thirst drive and may aid rehydration. Elderly, active individuals need to use more caution as their sense of thirst is diminished with dehydration.

“Under heat stress, children’s exercise tolerance time is reduced compared to adults,” says Dr. Roberta Millard, a sports medicine specialist at Penn State Hershey. “For that reason, children should be encouraged to drink more fluids than dictated by thirst alone.”

Individuals engaged in vigorous exercise or whose work involves sweating for two or more hours daily should especially take precautions in the heat. The appearance of urine can also be helpful to monitor fluid intake. If well-hydrated, your urine should have the appearance of lemonade. If your urine is dark and has the appearance of apple juice, you should drink more.

Drink up – and drink early
Hydration should begin prior to physical activity or work in the heat by drinking at least two cups of water or sports drink one to two hours prior to exercise. In hot weather, drinking between a half-cup and a whole cup of fluid for every 15 minutes of vigorous exercise is a general guideline. Drinking cool fluids does double duty, both hydrating and cooling of the body.

By knowing your limits, dressing appropriately and drinking the right things, you can stay safe during summertime exercise, and ensure the benefits you realize are not outweighed by heat-related illnesses that can take a toll on the body.

 Source: Penn State Milton S. Hershey Medical Center