Hawai'i's reputation as an ideal playground for recreational athletes is founded on the reality of clear skies and sunshine virtually all year long.

But year-round sunshine, especially in our signature high-humidity summer months — requires year-round vigilance for dehydration, heat exhaustion and other dangerous conditions.

At this week's U.S. Youth Soccer Far West Regionals at the Waipi'o Peninsula Soccer Park, as many as a dozen players and spectators have been treated for dehydration and heat-related illness.

The prevailing assumption is that many others suffered minor heat-related symptoms that, while easily avoidable, could have escalated to more serious conditions.

Cynthia Shimoda and Alison Kuramoto are among a team of athletic trainers on hand to treat the estimated 8,000 players, coaches, spectators and administrators on and around the fields this week.

Both have seen their share of overheated athletes in need of cooling care, and both are quick to emphasize that nearly all of the cases they've seen could have been avoided.

"If you're thirsty, it's already too late," Shimoda says. "You're already dehydrated."

As Shimoda notes, proper hydration is crucial for the body's highly efficient cooling mechanisms to work properly.

Under normal conditions, the body reacts to excessive heat by sweating. As perspiration evaporates from the skin, the body slowly cools. (Heat is also lost by breathing out moisture.)

However, if a body is not properly hydrated, the system can't work as efficiently as it should and the resulting accumulation of excess heat begins to quite literally cook the person from the inside out.

"When you're sweating, your skin will be cool and clammy," Shimoda said. "But when you stop sweating, the skin dries. At this point, your body is going into shock and is shutting down."

Dehydration may result in heat exhaustion, the symptoms of which include heavy sweating, cramping, nausea, fatigue and dizziness.

Untreated, heat exhaustion can progress into heat stroke, a potentially fatal condition that occurs when the body's temperature exceeds 104 degrees.

Symptoms of heat stroke may include rapid heartbeat, elevated or lowered blood pressure, confusion, headache, nausea and fainting.

Ultimately, heat stroke may result in organ failure, coma and death.

Shimoda and Kuramoto say maintaining proper hydration is an ongoing process. They advise athletes to stay hydrated well before the start of any athletic event. Consuming at least eight ounces of water or sport drink before an event should ensure a healthy start.

Athletes can also minimize the enervating effect of the sun by wearing light breathable fabrics (synthetics like DryFit work well in wicking away moisture for proper evaporation), applying and reapplying sunscreen (minimum spf 30), and shielding themselves with UV-protective sunglasses, hats and umbrellas.

Once activity begins, athletes need to rehydrate regularly, though the exact amount will vary based on exertion and climate conditions. Endurance athletes, for example, are advised to drink six to eight ounces of fluid every 20 minutes.

One reliable measure is the so-called pee test: If an athlete's urine is clear, he or she is adequately hydrated. If it's dark yellow, chances are dehydration is occurring.

As many young athletes learned this week, humidity can exacerbate heat-related problems because moisture in the air can impede perspiration.

Mild dehydration can be treated by drinking water and/or sports drink (maintaining electrolyte balance is important to allow muscles to absorb fluid), changing into dry clothes, applying cool towels and resting.

More serious forms of heat exhaustion may require immediate icing, an IV infusion for faster rehydration, and immediate medical attention.