Exercise might be good for your health – but keeping fit without a good sports bra is bad for your chest. Research shows that the up and down movement of breasts during sports stretches vital ligaments beyond repair. And without the right support both small and large-chested ladies will end up with a saggy bosom.

During high-impact exercise, such as aerobics, unsupported chests can bounce by as much as 21cm, and move from side to side. This causes the breasts’ main support system, the Cooper’s ligaments, to be put under stress. Once these ligaments are stretched they never recover and that causes the chest to sag.

Even lower-impact sports can lead to chest bounce. A University of Portsmouth study found that breasts move as much during slow jogging as when sprinting. Other activities that necessitate a sports bra include aerobics, body attack and trampolining.

Women with smaller chests will also be affected by so-called “Cooper’s droop”. Medical research has found that whether you measure a 34A or a 36E, the supporting ligaments are under strain.

A sports bra is a girl’s best friend

An Australian study revealed that a good sports bra will reduce vertical bounce by half that of a bare chest. But to make sure you attain the right support it’s essential that you buy exactly the right bra size.

Always try on a range of bras to ensure good support and comfort.

Bra fit:

Bra comfort:

It’s also recommended that you change your sports bra every 30 to 50 washes. Keep an eye on the material to check for wear and stretch. There is little point in a bra that sags or doesn’t support you in the right places.

Where to buy your sports bra:

* Most good sports shops will stock a wide range of bras. Make sure you try a number on to ensure you get the right fit.

* Supermarkets and department stores now also sell sports bras.

* Bra-specific on-line stores will have the widest range of many different sizes and styles. A good on-line store will offer a personalised measuring service – and will allow you to return bras that do not fit perfectly.