If you click the link at the top you'll find it goes to an article. The article will often expand upon the text in the link!!!

In this case:

"While we would expect children's lungs to grow year on year, our results indicate that the London children's lung growth had accelerated during the four years to 'catch up' with the control group in Luton to reach similar levels of lung capacity," researchers say.

"I was absolutely stunned when I first saw the results," Prof Chris Griffiths, a senior author on the study, at Queen Mary University of London, told the BBC.

"The speed of catch up in lung capacity in the London group was surprising and impressive."