We’re all very aware that our boobs bounce. Anyone who’s run for the bus or up some stairs would have figured this out. But why? Well we’re about to reveal all!

Boobs tend to bounce as they are the body part that is most affected by gravity – which you probably have already guessed. On average they weigh around 3 lbs each (which of course varies depending on size) and there is very little natural support to hold them still.

On average, a woman’s breasts move 9cm with each step you take and this isn’t just up and down, but sideways too. Without alarming anyone, if boobs are unconstrained by a bra, breaking into a run could see your boobs move up to 15cm with each stride. If this doesn’t make you instantly want to wear about four sports bras I don’t know what will! To put this into perspective, this means that if an average D-cup size woman takes part in a one kilometre jog of over 1,000 steps her boobs will have independently journeyed as much as 0.12 kilometres. Ouch.

jogger runner exercise

It seems strange to say, but each individual boob will have its own movement pattern. But unfortunately as we mature, the older we get the further our boobs travel. A study carried out by Portsmouth University’s Research Group in Breast Health – which used hi-tech sensors and 3D scanning to analyse the motion of breasts – monitored the boobs of two sets of women, aged 18 to 25 and 45 to 65, during brisk walks. Researchers discovered that while the younger women’s breasts mainly moved up and down, the older group’s bosoms moved more in all directions.

Professor Joanna Scurr, an expert in bio-mechanics of breasts, said ‘In all women, their right and left boobs move differently, depending on mass and how elastic they are. However in older women, there is more movement in both breasts, probably because the supporting structures are not as strong. You will tend to see a more U-shaped swing.’

So it seems gravity is of course the main culprit to why our boobs move, but it’s also interesting to find out that they move in all sorts of directions and quite a way depending on exercise! This is why we bang on about how important it is to wear a sports bra. We hope you found this as informative as we did – and will now never run up the stairs without a bra again! Does this mean we get out of exercising all together? We think so.

Grace x

Find the perfect sports bra for you by reading through our Sports Bra Buying Guide!

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