What SPF Should You Use to Exercise Outside?

Many people find exercising outside preferable in the good weather. The fresh air and sun helps you enjoy your workout more. In some cases, according to "The New York Times," you challenge your body more with harder workouts and more stretching. It's important to protect yourself from the strong rays of the sun when you exercise outside. Ultraviolet rays can lead to skin damage and potentially life-threatening forms of skin cancer. Choose a sunscreen product with an appropriate SPF rating to stay safe.

SPF Explained

• SPF refers to the sunscreen's ability to protect you from harmful UV rays. The number relates to how much longer you can stay in the sun without getting a sunburn. The Skin Cancer Foundation explains that a product with SPF of 15 means you can exercise or enjoy the outdoors 15 times longer than you could without sunscreen, without burning. This is about five hours, as many people begin to burn within 20 minutes. Sunscreens with SPF 2, the lowest available, block about half of the sun's radiation, while SPF15 filters as much as 93 percent of harmful rays, according to the American Melanoma Foundation.

Recommendations

• The U.S. Food and Drug Administration recommends using a sunscreen with SPF of at least 15 when you're outdoors. At this level of protection, the majority of the UV rays will be blocked. The U.S. Tennis Association recommends that tennis players -- and others who exercise outdoors for long stretches of time -- protect themselves more with higher SPF numbers. Wear a hat, sunglasses and long sleeves as additional safeguards.

Application

• Apply sunscreen about 30 minutes before you head outside to exercise. This gives the lotion, spray or stick time to bind to your skin to give you the most protection possible. Use sunscreen liberally to ensure that you are fully protected. An ounce of sunscreen -- approximately the amount that would fit in a shot glass -- achieves this goal. Even if you're wearing a high SPF number, you'll need to reapply the sunscreen every couple of hours, or sooner if you've been in the water or perspiring.

Water Exposure

• Some types of sunscreen, often labelled as "sport" versions, are waterproof or water resistant. Waterproof varieties continue to shield you from UV rays for up to 80 minutes after you are exposed to water, either through sweating or swimming. Water-resistant products offer protection for 40 minutes. It's a good idea to slather on some more sunscreen after your swim practice or water aerobics class just to be on the safe side.