Mountain bikers spend a good amount of time in the sun. While a little bit of sunlight is a good source of Vitamin D, too much exposure can be harmful. Since avoiding the sun altogether is not on the agenda for those of us who like to play outside, we wanted to find out the best ways for outdoor enthusiasts to protect themselves from harmful UV rays and prevent skin cancer.

We turned to the experts to find out: Jeanie Chung Leddon, MD, PhD, board certified dermatologist and fellow of the American Academy of Dermatology; Deborah S.

Sarnoff, MD, board certified dermatologist and senior vice president of The Skin Cancer Foundation; and Joel Schwartz, DO, radiation oncologist with Illinois Cancer Specialists, a practice in The US Oncology Network.

Read on for expert skin protection tips from Drs. Leddon, Sarnoff and Schwartz.

About.com: What is skin cancer and how is it caused?
Dr. Sarnoff: Skin cancer is the uncontrolled growth of abnormal skin cells. It occurs when unrepaired DNA damage to skin cells (most often caused by ultraviolet radiation from sunshine or tanning beds) triggers mutations, or genetic defects, that lead the skin cells to multiply rapidly and form malignant tumors.

Dr. Schwartz: Skin cancer is an abnormal growth of the skin cells. It can be unsightly and bothersome in the case of Basal Cell Carcinoma and most Squamous Cell Carcinomas. It can also be dangerous and deadly in the case of Melanoma. There are multiple triggers that can lead to a skin cancer. An individual may have a genetic predisposition for producing a skin cancer.

In addition, environmental factors can also cause genetic damage that can produce a skin cancer. These factors include a lifetime of excessive sun exposure, tanning bed usage, or 5 or more blistering sunburns in early childhood.

About.com: Which skin types are at a higher risk of skin cancer?
Dr. Schwartz: Fair-skinned people are at greater risk than those with darker skin. This is because darker skinned people produce more melanin, the pigment that gives color to skin and hair, and protects the skin from the damage of ultraviolet radiation. In addition, people with blue or green eyes and red hair or blond hair are at increased risk.

Dr. Leddon: Below skin types have higher risk of skin cancers because they typically have fair skin with less pigment.
Skin type I: You always burn and never tan in the sun
Skin type II: You almost always burn and rarely tan in the sun.
Smokers and people who use indoor tanning devices also have higher risk for skin cancers. People with a family history of melanoma skin cancer or many moles or abnormal appearing moles can be at higher risk for melanoma skin cancers.

About.com: What are the best ways cyclists can protect their skin from the sun?
Dr. Schwartz: Top on the list is sunscreen. Consumer Reports reviewed sunscreen products in May of 2014 and they have an excellent list of quality sunscreens. The tube you select should be a broad-spectrum sunscreen offering protection against both UVA and UVB rays and have an SPF rating of 30 or greater. Cyclists sweat a lot and like swimmers, they should use a "water resistant" sunscreen. Also, re-apply sunscreen every 2 hours (since it may "wash off" with a lot of perspiration and activity). Sun protective clothing is just as important. Cover up with high quality active wear that has a UPF (ultraviolet protection factor) rating of 30 or greater. Polyester, nylon, wool, silk and denim are very good at stopping UV light. Cotton is much less effective. Lastly, the face is a very common area for skin cancers to develop. Using a helmet with a visor and UV-blocking sunglasses will also keep your face more protected.

Dr. Leddon: For sun protection, wear clothing and a broad-rimmed hat with a UPF of 30 or higher or dark or bright colored tight weave clothing, use broad spectrum sunscreen with SPF 30 or higher and reapply at least every 2 hours. Cyclists should wear sunscreen under their gloves. Physical blockers containing Zinc Oxide or Titanium dioxide are good options as they stay on better in sweat than chemical blockers. Avoiding the sun during the hours when the sun is at strongest between 10 am to 4 pm is also recommended. Seek shade when possible. 

(Read part two of this article on skin protection.)