Swimmers, runners, tennis players, golfers and other athletes often train and compete during the most sun-damaging hours of the day - between 10am and 4pm.
However, you might not want to wear a hat or long sleeves. And sunscreen might make you feel as if your pores are clogged and you cannot sweat, which is essential for cooling down.
That is how Mr Patrick Serfass, a Washington resident and triathlete, said he feels about sunscreen. He will wear it reluctantly while training but he said that it affects his performance.
So on race day, he goes sunscreen-free and deodorant-free to sweat more and cool better.
He said: "My body can sweat more easily, which means I cool faster, and that's key for performance."
Why do people even bother to run or play tennis or golf during peak sunshine hours? Can't they train in the early morning or late at night?
DARK SKIN IS NO PROTECTION
I have dark skin, dark eyes and dark hair.
I never thought it would happen to me. We need a cultural shift... we now know that skin cancer can happen to anyone.
SUMMER SANDERS, a 1992 Olympic gold-medallist swimmer who has had three melanomas removed.
Not if you need to make sure your body can handle the conditions under which you will be competing, Mr Serfass said.
Failing to do so "can kill your race", he said. "You have to get your body used to the heat and humidity."
Before moving on to other sun- blocking options, athletes can take a look at sunscreen products in the market: What type? How much? When to apply?
"You want a product with SPF30 or more, broad spectrum and water resistant," said Dr J. Leonard Lichtenfeld, deputy chief medical officer at the American Cancer Society, referring to the sun protection factor, which measures how well sunscreen protects your skin.
"And follow the directions. Reapply and use generous amounts," he added.
Take note that there is no such thing as building a base tan.
A tan - any tan - is a sign that skin is unhealthy, Dr Lichtenfeld said. "It's the skin's way of saying, 'I have a problem'."
Dr Marty Braun, a dermatologist, recommends a daily lotion or face cream that includes SPF, even if it is as low as 15.
For prolonged outdoor activity, he recommends SPF30 or higher.
If you want to be completely covered, use sunscreens that have physical blockers, as opposed to chemical blockers such as zinc and titanium.
Dr Braun knows that athletes have a resistance to blocked pores and having to reapply mid-match or mid-race.
Like Mr Serfass, he also recommends wearing sunscreen when you train and going without it only when you compete. It is not a perfect solution, but it helps.
Another way to shield yourself from damaging rays is to wear protective clothing - such as broad-brimmed hats and long- sleeved shirts - though it is hard to imagine any athlete wearing a broad-brimmed hat.
Dr Braun said: "I don't think we'll convince tennis players to wear sombreros when they play."
A hat that shades the face and head will do. You could apply sunscreen on the back of your neck and ears, which are common areas for skin cancers.
There are also lightweight, long-sleeved workout shirts that are sun-protective.
To stay cool while wearing sun- protective clothing, Mr Serfass said, carry two bottles of water on long training runs and rides - one to spray yourself with and the other to hydrate.
And if you are wearing a hat, you can fill it with ice when it is really scorching.
Children need to be careful too.
Swimmer Summer Sanders, a 1992 Olympic gold medallist who has had three melanomas removed, said she hopes parents and coaches will help their children stay clear of sun damage.
She now promotes skin cancer education for young lifeguards and swimmers through the group Block The Blaze.
"I have dark skin, dark eyes and dark hair. I never thought it would happen to me," she said.
A tan body is not a sign of health, she said.
"We need a cultural shift. Knowledge is power and we now know that skin cancer can happen to anyone," she added.
THE WASHINGTON POST