Health news: Why going to the gym could be making you sick.

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Fact: When you walk through the doors of a gym, you immediately feel healthier.

God, even owning a gym membership makes you feel healthier, even if you never actually make it into the building. Hundreds of fit (or soon-to-be-fit) people go there every day, so you become one via osmosis. That’s just how it works.

But what if we told you that going to the gym could actually be making you sick? And no, we’re not talking about the perils of shared yoga mats or sweaty, barely towelled-down equipment – it’s something a lot harder to avoid.

Why you should avoid the communal yoga mats at your gym

Researchers from Holland and Portugal have found the airborne pollutants inside fitness centres could pose risks for the health of gym-goers. Air quality monitors installed inside the studios and bodybuilding rooms of 11 gyms in Lisbon detected high levels of dust, carbon monoxide, carbon dioxide, formaldehyde and particle pollution in the air during peak times.

These pollutants can exacerbate respiratory problems like asthma - and according to study author Carla Ramos, the body is more exposed to them during a workout.

"When we exercise, we take in more air with each breath and most of that air goes through the mouth, bypassing the natural filtration system [in the nostrils]. The pollutants go deeper into the lungs compared to resting situations."

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"We consider that the gymnasiums meet the criteria for a poor indoor quality," the conclusion of the report reads.

"The pollutants CO2, VOC and CH2O presented high concentrations exceeding the national limit values." Well, that's a bit concerning. These elements were particularly high during classes, due to the number of people (sadly, that includes you) adding toxins and CO2 to the air by exhaling through the mouth. Dust and fumes from the carpet and furniture in these smaller rooms was also easily disturbed at busy times.

However, before you wield this information as an excuse not to exercise (we're onto you, lazy girls), it's worth noting that air pollutants like those mentioned above can be found in numerous environments we spend time in every day - even our own homes and offices.

What to do with that gym membership you never use

According to the study authors, gyms should try to optimise their air conditioning and heating systems and ventilation. Likewise, if you're really concerned about being exposed to air pollutants, maybe try to visit the gym at quieter times, or find a spot with good ventilation - but don't cancel your membership based on these findings.

Alternatively, you could move part of your exercise to this big, vast, thing we call "outside". You don't have to look too far to find beautiful parks and running tracks that'll get your heart pumping and fill your lungs with fresh air - and you don't need to pay a membership fee.

Have you ever felt uneasy about the hygiene at your gym?

Regardless of whether you work out inside or outdoors, consider this your easy guide to the fitness accessories that are worth the money - and the ones that definitely aren't: