'Runner's boob' is increasingly being reported to GP’s but what is it? GP's are noticing more runners are visiting their GP complaining about pain in their breasts from running, so we look at why Heres everything you need to know about runners boob.

Why do your breasts hurt after running?

When studying the movement of the breasts, scientists have found that when you run, your breasts move in a figure of eight pattern, not up and down. This means no matter how far your legs are running, your breasts are running further. In fact, researchers at Portsmouth University’s Research Group in Breast Health (RGBH) calculated that the breasts can move 15cm during a run.

Another recent study, conducted by running brand Brooks, found that running in the wrong sized bra can shorten your stride, by four centimetres. This could add up to running an extra mile or 1.5 kilometres over the length of a marathon.

In a survey of 1,397 entrants to the 2012 London marathon, a third had experienced breast pain during training. But why do they hurt? Discomfort, chafing or caused by running is strain on the breasts Cooper’s Ligaments - the supportive tissue.

Unlike other muscles in the body, once the supportive tissues in the breasts stretch, they cannot revert back to their original position. However avoiding irreversible sagging is easier than it sounds.

How can you reduce pain?

According to the NHS website, research suggests 70% of women are wearing the wrong bra size. What’s more, as the breasts are composed of fat and fibrous tissues, as you eat better and exercise more, your breasts may decrease in size, meaning your sports bra might not be supporting them as well as it once did. Your sports bra also loses it's support overtime, with experts recommending you Valencia Marathon 2024: New world record ahead.

Could there be a World Treadmill Championships RGBH, says women need better advice on getting the right fit when it comes to sports bras. 'The most common mistake is to wear the underband too loose and the cup size too small', she says.

What style of sports bra is best?

Like trainers, different brands and styles of sports bras will suit different women better. For women with smaller breasts, often compression-style sports bras are comfy, which work by pressing your breasts against your chest - you normally need to pull these on over your head.

Alternatively, encapsulation bras fit like a normal bra, lifting the breasts and with adjustable straps, and can be a better choice for women with larger breasts who want to adjust the support. There’s also some bras on the market that do both. We’ve rounded up Runners World, Part of the Hearst UK Wellbeing Network, and found advice for women with larger breasts when it comes to looking after them when running.

It's important to note, breast pain is breast pain, and if you are worried by a new or unusual pain, it’s a good idea to go and check with your doctor.