SUN EXPOSURE AND EXERCISE: The Good, the Bad, and the Behavior Change : ACSM's Health & Fitness Journal

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The Good, the Bad, and the Behavior Change

Lynn, Jeff Ph.D.; Urda, Joyan Ph.D.; Pierce, Patricia Ph.D., FACSM

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ACSM's Health & Fitness Journal 20(3):p 11-15, May/June 2016. | DOI: 10.1249/FIT.0000000000000200
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With spring and summer on us, more of our clients venture outdoors to enjoy physical activity in the bright sunshine. Outdoor activities can be invigorating and a welcome change of pace for those who have spent the winter indoors. We all are familiar with the physical and psychological benefits associated with exercise, but some may be less aware of the benefits associated with sun exposure. Spending time in the sun has been shown to activate vitamin D, enhance mood (7), improve sleep quality (3), and positively affect blood pressure (4). People suffering from seasonal affective disorder often are encouraged to spend time outside in the midday sunshine because exposure to bright light may help to reduce symptoms (7).

Considering the positive effects of both exercise and sun exposure, it may seem that outdoor exercise with abundant sun exposure is the perfect prescription for health. However, there are risks associated with sun exposure. UV radiation from the sun includes potentially damaging UV-A (longer wave) and UV-B (shorter wave) radiation. Overexposure to both of these UV rays can cause irreversible skin damage, accelerated skin aging, and a variety of skin cancers (6). The UV-B rays, which increase intensity in the spring and summer, are responsible for tanning and burning, both of which are signs of DNA-mediated damage to skin cells and relate to an increased cancer risk. In fact, Dermatologist Brad Amos, M.D., Ph.D., FAAD, likened a person showing off his suntan to an alcoholic bragging about his cirrhosis of the liver.

UV rays are responsible for both initiating skin cancers and promoting their growth, a fact that should be taken seriously by those who spend time exercising outdoors. In the United States, nearly five million people each year are treated for skin cancer, and during the past 30 years, there have been more cases of skin cancer than all other cancers combined. Basal and squamous cell carcinomas are the most common, and 90% of these are associated with sun exposure. Melanomas, although less frequently diagnosed, account for the large majority of skin cancer deaths, and 86% of melanomas are associated with exposure to the sun’s UV rays (9).


A less drastic but quite common risk of UV exposure is sunburn. Although sunburns may lead to permanent skin damage and increased cancer risk, a more acute consequence of sunburn that can affect exercise performance is the fluid shift and microswelling of the skin, which may compromise body temperature regulation. The eyes also can be damaged by sun overexposure including the formation of cataracts, ocular melanomas, and macular degeneration.


As little as 15 minutes of sun exposure has been shown to increase the risk of sun-related skin damage in runners. This finding suggests that any outdoor exercise carries risks. In 2006, a study of marathoners and matched controls concluded that runners presented with an increased risk of malignant melanoma and nonmelanoma skin cancer (1). Furthermore, high-intensity and long-duration training can suppress immune function, which may accommodate the development of some skin cancers (5).

Athletes who train/practice outdoors, particularly during peak hours for UV radiation (10 a.m. to 4 p.m.), are at risk for overexposure. A study including 290 NCAA athletes reported an average outdoor practice time of 4 hours per day, 10 months out of the year, for a total of 1,000 hours of potential annual sun exposure (10). Unfortunately, sweating has a dual negative effect of increasing skin photosensitivity and washing away sunscreen.

The surface on which one exercises also may increase sun exposure. Sand reflects 10% to 15% of UV radiation, whereas ice and snow reflect up to 80% of the sun's rays. For those who enjoy skiing or mountaineering, be aware that every 1,000 feet of elevation gain increases UV intensity by 8% to 10%. The good news for those on ice or snow is that cold temperatures often prompt the wearing of plenty of clothing, which conveys protection. Conversely, many sports, such as beach volleyball, require clothing that ensures abundant skin exposure on a surface that is highly reflective of UV rays.


Finally, those who oversee children during outdoor sports and activity should be aware that, in general, the younger the child is, the greater his or her sensitivity to the sun. UV radiation exposure during childhood and adolescence has a greater impact on melanoma risk than exposure during adulthood (2), so protection strategies are critical for youth participating in outdoor sports and activities.



The most effective strategy for reducing sun exposure risk during outdoor exercise is to cover your skin with clothing and a hat. The more skin that is covered, the better. Ideally, outdoor exercisers should wear long sleeves, pants, sunglasses, and a hat with a brim. Of course, not all clothes are created equally. The UV protection factor (UPF) is an indication of the clothing’s ability to block UV rays. A higher UPF means greater protection. Dark colors, polyester, rayon, and wool tend to have a higher UPF than light colors and cotton. Interestingly, laundering cotton can increase its UPF because of shrinkage of the fabric, which increases the density of the weave. Conversely, when cotton becomes wet, it loses most of its UPF. This is an important consideration for those who may be sweating profusely or wearing cotton while exercising/playing in water. Also, any clothing's UPF is diminished as the fabric becomes more worn or stretched through time.

BOX 1:
Sun Protection Strategies

Sunglasses are an essential piece of sun protection, but choosing the right pair has bearing on both comfort and how well they protect your eyes. Sunglasses should have lenses large enough to keep the sun out of the eyes from all angles, and they should be rated to block 99% to 100% of both UV-A and UV-B rays. It also is important that they have a nosepiece that will resist slippage when the skin gets sweaty. These points should not be overlooked when choosing sunglasses for children. Parents should be advised to avoid the cutesy glasses in favor of real, impact-resistant, UV-blocking sunglasses. This is particularly important for children younger than 10 years because of an elevated risk of UV penetration through the clear lenses in their eyes (9).


The advice from the American Academy of Dermatology for anyone spending time outdoors is to apply 1 oz of a broad-spectrum sunscreen with a sun protection factor (SPF) of 15 or higher 15 minutes before exposure and reapply every 2 hours. But what does all this mean? A broad-spectrum sunscreen is a mix of several chemicals that protect against both UV-A and UV-B radiation. Using a broad-spectrum sunscreen is important because it is the only way to know that you are being protected from UV-A rays. There is no rating for the effectiveness of sunscreen at blocking UV-A radiation. The SPF is a measure of the product's effectiveness to prevent sunburn caused only by UV-B rays. The SPF is theoretically a multiple of the time it takes for a person to get sunburn. For example, if you would normally burn in 10 minutes, an SPF of 15 should extend the time it takes to burn by 15 times, or 150 minutes. Another way to evaluate SPF is by how much of the UV-B rays it filters. SPF 15 filters approximately 93% of UV-B rays, whereas SPF 30 and SPF 50 filter approximately 97% and 98%, respectively. So, although an SPF of 15 is effective, those who have sensitive skin or a high risk for skin cancer should consider an SPF of 50. It should be noted that no sunscreen can block 100% of UV radiation, and redness of the skin is caused by UV-B rays and is not an indicator of UV-A damage, so a lack of sunburn is not equivalent to a lack of damage.

BOX 2:
Sun Protection Factors

Regardless of the sunscreen used, effectiveness diminishes throughout the day, and sweating or exercising in water accelerates the process. People who are not exercising and sweating should reapply sunscreen every 2 hours. When exercising and sweating in the sun, the recommendation is to reapply every 40 or 80 minutes depending on the specific sunscreen being used. Water-resistant sunscreens are preferable during exercise because they offer more protection while sweating, and they are less likely to run into the eyes. The U.S. Food and Drug Administration (FDA) defines the term water resistant as maintaining its SPF while wet for 40 minutes. They define very water resistant as maintaining SPF for 80 minutes while wet. Labeling laws on sunscreen packaging require the manufacturer to disclose this information. In addition, there is no such thing as waterproof or sweatproof sunscreen, and the FDA banned the use of these terms in 2013.

Time of Day

When possible, exercise should be performed before 10 a.m. or after 4 p.m. when the sun's rays are less direct. This schedule may not be an option for athletes who have scheduled practice during midday or people whose life obligations preclude early morning or evening exercise. Those exercising at midday should be aware that even on overcast days, up to 80% of the sun's UV rays can penetrate the clouds. If exercise is performed in the middle of the day, one should seek shade when possible, wear protective clothing, and apply a broad-spectrum water-resistant sunscreen.


Barriers to Use of UV Protection

There are a variety of barriers exercisers identify for not protecting themselves from harmful UV rays. One barrier to protection is a lack of knowledge of the associated dangers or the belief that the negative consequences will happen only to others. Some exercisers report having the desire to have a suntan because many believe that suntanned skin conveys a healthy or attractive look. Others believe that cloud cover protects them from UV radiation, which is not true. A common misconception is that 80% of lifetime sun exposure occurs before age 18 years, so adults need not be so concerned. The truth is that only approximately 25% of total sun exposure occurs before age 18 years, and men older than 40 years are the ones who spend the most time outdoors.

As stated earlier, clothing is the best barrier to sun overexposure. However, wearing minimal clothing often is perceived as most comfortable and ideal for trying to stay cool while exercising on a hot day. For instance, more than 95% of marathon runners wear shorts and shirts that leave the back and/or extremities uncovered (1). Furthermore, some fear that wearing a hat will interfere with heat dissipation even though research demonstrates that this is not true.

A common reason that exercisers cite for not wearing sunscreen is that it is not readily available or they simply forget. It would be prudent to advise all exercisers to carry sunscreen in their gym bags and consider it to be essential equipment. Coaches and personal trainers consistently should encourage its use. Some corporate wellness sites have sunscreen dispensers on the wall near the doors where employees leave to exercise outdoors.

Many exercisers report that they do not like the greasy feel of lotion or that sunscreen runs into and burns their eyes when they sweat. The good news is that water-resistant sunscreens are less likely to drip into the eyes, and plenty of exercisers have posted online that they have a favorite sunscreen that does not burn their eyes. It may take a bit of looking to find the one that works for each individual. It should be noted that all of the benefits of sun exposure listed earlier, including vitamin D activation, occur with minimal time in the sun and are not negated by wearing sunscreen.

Behavior Change Strategies

Many reading this article are in a position to provide health, wellness, and exercise guidance to others. The important question is: what is the most effective approach for facilitating sun protection behavior change? Unfortunately, reports from research indicate that few people improve sun protection strategies after interventions. However, there is excellent information to be drawn from the behavior change and wellness coaching literature on this topic, and perhaps the best chance for success lies in following these known principles.

Behavior change is a process, and evaluating the pros and cons represents decisional balance or the way each individual assesses the relative importance placed on the potential advantages or disadvantages/barriers to adopting a healthy behavior. Lack of readiness to change should not be confused with lack of desire to change a behavior; the individual may just be overwhelmed by having too many barriers to overcome. Accordingly, efforts to increase value on the pros of behavior change are more likely to result in actual behavior change than effort spent to reduce the cons.

The transtheoretical model of behavior change contends that the behavior change strategy used should be matched with an individual's “stage of change.” The stages (simplified here) are precontemplation, contemplation, preparation, action, and maintenance. Precontemplators are more likely to believe that negative outcomes will not happen to them, and they are not considering changing. These people would most benefit from awareness and education about risks as well as a clear understanding of the positive outcomes of adopting sun protection behaviors in contrast to the negative consequences of not adopting these strategies.

BOX 3:
Sun Protection Behavior Change Strategies

People in the contemplation and preparation stages are likely to understand reasons to change, as evidenced by the fact that they already intend to make positive changes, but they can benefit from creating specific action plans. They can be guided by asking them to answer such questions as, “When and where will you buy clothing and sunscreen?”, “When and where will you be exercising?”, and “How will you make sure to pack sunscreen and apply it before heading outdoors?” There is additional benefit to asking them to realistically envision the barriers to these new behaviors that will arise and how they will overcome these barriers.

People in the action stage of change have already adopted sun protection behaviors but not for a long period. They probably do not need education about pros and cons, and they have found some success with the strategies they have tried. They may benefit from conversations about what could cause relapse and how to avoid or overcome these situations. It also may be valuable for those in any stage of behavior change to deeply consider and articulate their personal motivations to adopt or maintain the healthy behaviors and avoid the negative consequences of not enacting these behaviors.

There is evidence that sun protection strategies improve when a physician counsels the patient on the topic, and it is recommended that those who exercise outside receive an annual skin examination from their doctor. After learning what to look for, a monthly self-examination also is suggested (8). Exercise facility managers should consider posting sun protection educational messages where clients are likely to see them. If it fits the budget, providing sunscreen to clients when you lead outdoor exercise is a great idea. Sadly, one of the strongest cues to action in terms of UV protection is a personal cancer scare. If leaders in the health/wellness and fitness fields can better educate, encourage, and guide clients toward protective behaviors, perhaps more people can enjoy the remarkable benefits of outdoor exercise with less risk of skin damage and cancers resulting from overexposure to the sun.


Exposure to sunshine conveys psychological and physiological benefits, but risks associated with exposure to the sun's UV rays must be addressed. Skin cancer is, by far, the most diagnosed cancer, and outdoor exercisers are at risk because of cumulative UV exposure and inadequate protective behaviors. Those who exercise outdoors should consistently wear protective clothing and a broad-spectrum water-resistant sunscreen with a sun protection factor of 15 or higher. Using evidence-based behavior change strategies provides the best opportunity to guide clients toward adopting appropriate sun protection behaviors.


The authors thank Chad Mathews, PA-C, for his guidance and support and for sharing his expertise from 15 years of experience working in dermatology and educating students on the importance of sun protection.

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Sun Exposure; UV Radiation; Skin Cancer; Sunscreen; Behavior Change

© 2016 American College of Sports Medicine.