Every time you train outdoors you are exposed to two types of ultraviolet radiation with very different effects: UVA and UVB. Understanding the difference is not a theoretical exercise. It is the first step in choosing sun protection that actually works for those who play sport, not for those who sunbathe while staying still.
The electromagnetic spectrum in simple terms
Sunlight reaching the Earth is made up of different wavelengths. Part of it is visible light, which we perceive with our eyes. Another part is infrared radiation, which we perceive as heat. A third part is ultraviolet (UV) radiation: invisible to the human eye, but responsible for most of the sun's effects on the skin.
UV radiation reaching the Earth's surface is divided into two main bands:
- UVA — longer wavelength (315-400 nm), penetrates deeper into the skin
- UVB — shorter wavelength (280-315 nm), acts mainly on the surface layers
UVC (100-280 nm), the shortest and most energetic band, is almost completely absorbed by the Earth's atmosphere and does not reach the surface under normal conditions. This is why sun protection communication almost always refers only to UVA and UVB.
This distinction is not merely terminological. UVA and UVB interact with the skin differently, at different depths and with different biological effects. Protection designed to cover only one of the two bands leaves the other uncovered, which is why talking about “sun protection” without specifying which spectrum it covers is not sufficient information for those who train regularly outdoors.
UVA: the exposure that ages skin over time
UVA accounts for around 95% of the ultraviolet radiation that reaches the ground. It penetrates deeper into the dermis, where it acts on collagen and elastin fibres: chronic UVA exposure is one of the main factors in skin photo-ageing, including wrinkles, loss of elasticity and the spots that appear with years of accumulated exposure.
The effect of UVA, however, is not limited to the aesthetic level. Beyond photo-ageing, it generates oxidative stress in skin cells and can indirectly damage DNA, also interfering with normal cell repair mechanisms. Research recognises this mechanism as playing a role in the increased risk of skin cancers, including melanoma — a contribution that adds to that of UVB. Precisely because UVA exposure is chronic, cumulative and without warning signs such as sunburn, broad spectrum protection remains the most complete way to cover both damage mechanisms.
Unlike UVB, UVA is present with similar intensity throughout the year and passes through clouds and glass. This means exposure continues even on cloudy days or during activities considered “sheltered”, such as training near a window or on a day perceived as not very sunny.
UVB: the rays that burn
UVB accounts for a smaller share of UV radiation (around 5%), but has higher energy and acts mainly on the surface layers of the skin. It is directly responsible for sunburn and plays a central role in the cellular DNA damage that accumulates over time.
UVB intensity varies much more than UVA: it changes with the time of day, the season, latitude and altitude. It is at its highest during the central hours of the day and in the summer months, but remains significant in the mountains and at altitude throughout the year.
UVA and UVB differences: comparison table
A quick summary of what has been covered so far, useful as a reference.
|
|
UVA |
UVB |
|
Skin penetration |
Down to the dermis |
Mainly epidermis |
|
Cause sunburn |
No |
Yes |
|
Photo-ageing |
Yes, main cause |
Yes, to a lesser extent |
|
Link to skin cancers |
Yes (promoting oxidative stress and indirect DNA damage) |
Yes (direct DNA damage) |
|
Pass through glass |
Yes |
Almost completely blocked |
|
Present in winter |
Yes, with limited variation |
Yes, but reduced |
|
Variability of intensity |
Low |
High: varies with time, season, latitude, altitude |
UVA and sport: why those who train outdoors are doubly exposed
Those who play outdoor sport are not exposed to the sun occasionally, as can happen to those who spend the day in an office. They are exposed for hours, often during the periods of peak UV intensity.
This is why broad spectrum protection, effective against both UVA and UVB, is not an optional detail for those who play sport: it is the minimum standard to start from.
There is also a practical aspect linked to the duration of the activity. A one-hour training session involves very different UV exposure to a fifteen-minute jog: total time under the sun is one of the factors that most affects cumulative exposure, together with the UV intensity at the time, the altitude at which you train and the surface on which you practise sport. Asphalt, sand and water reflect UV in different proportions, increasing actual exposure even when under partial cover, such as a parasol or a tree.
How UVA protection is measured
Unlike SPF, which indicates the level of protection from UVB rays (the main cause of sunburn), protection from UVA rays is assessed with specific tests.
In Europe, the reference is the circled UVA symbol found on sunscreen packaging. This mark indicates that the product complies with European recommendations and that the UVA protection factor (UVA-PF) is at least one third of the stated SPF.
In Asian markets, on the other hand, the PA (Protection Grade of UVA) system is widespread, based on the PPD (Persistent Pigment Darkening) method. The classification ranges from PA+ to PA++++: the higher the number of “+” signs, the higher the level of UVA protection.
The term “Broad Spectrum” indicates that the product offers protection from both UVB rays, responsible for solar erythema, and UVA rays, associated with photo-ageing and long-term skin damage.
FAQ
Is UVA dangerous even if I never get sunburnt?
Yes. UVA does not necessarily cause visible reddening, but its action on collagen and elastin accumulates over time regardless of whether the skin burns or not.
Is protection with a high SPF alone sufficient for those who train outdoors?
A high SPF alone mainly protects against UVB. For complete coverage, broad spectrum protection is needed, effective against UVA as well.
If I wear sunscreen, will I not tan?
No. Sunscreen does not block tanning, but it reduces the damage caused by UV rays.
Even with SPF 50+ protection, a small amount of UV radiation reaches the skin and still stimulates the production of melanin, the pigment responsible for tanning.
The difference is that the tan develops more gradually and safely, reducing the risk of sunburn, cellular damage and premature skin ageing.
Does altitude affect exposure to UVA and UVB?
Yes. As altitude increases, overall UV radiation increases, and this is a factor to consider for those who train or play sport in the mountains. This is one of the scenarios SUNO ALPINE was developed for.
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Knowing the difference between UVA and UVB makes it possible to read a label with greater awareness and to assess a sunscreen for what it really offers, not just for its most visible SPF number.
SUNO formulas are designed for outdoor sports
All SUNO sunscreens are formulated to offer broad spectrum protection (UVA and UVB) and are developed with the needs of those who play outdoor sport in mind. Lightweight, sweat-resistant formulas designed to accompany activities such as running, cycling, trail running, trekking and mountain sports, where UV exposure is often intense and prolonged.
You can explore the characteristics of the different formulas and choose the one best suited to your activity in the SUNO Sport products section.
