Your cell phone may well be making one of your thumbs bigger

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Check for yourself! A new study claims that 1 in 20 adults in the U.K. think that one of their thumbs is bigger than the other, thanks to "swiping" on smartphone screens.

Telecommunications giant Telefonica claimed in a statement that the enlarged thumbs could be due to the increased workout of having to grapple with bigger handsets.

Of those respondents who believe their swiping thumb is bigger, the increase in size averaged out at an estimated 15 percent.

Nina Bibby, Marketing and Consumer Director, from Telefonica's subsidiary O2 said it's now accepted that smartphones have become an extension of us.

"It's difficult to tell where our hands stop and the handset starts. So in some ways it's no surprise that our bodies are subtly changing to adapt to the fact that mobiles are increasingly a part of our lives."

Also quoted in the release is hand therapist, Nicola Goldsmith, who doesn't dismiss the theory out of hand.

"Our thumb muscles are highly complex and located both in the base of the thumb as well as in the forearm, so an increase in "thumb swiping" could add to muscle strength and therefore bulk in these muscles.

However Carley King, professional adviser at the Chartered Society of Physiotherapy, said a bigger thumb could simply just be down to which hand you use most of the time.

"Increased use of a particular muscle group could lead to an increase in muscle bulk, but a difference in size of thumb could also just be due to which hand is dominant," she said in an email to CNBC Friday.

King said a bigger concern in her experience was that a repetitive action, such as swiping on your mobile phone, could lead to a Repetitive Strain Injury (RSI).

She recommended phone users adopt frequent rest breaks and a change of position.

The Telefonica study was carried out amongst 2,000 people.