She is about to undergo major surgery on her back that will put her out of action for several weeks.

And model Natalie Roser is making sure to fit in as much physical activity as she can ahead of the procedure.

The Miss Universe Australia finalist modelled a sexy exercise outfit as she played a game of tennis on Tuesday.

The blonde beauty showed off her abs in a black crop top and toned legs in a matching tennis skirt, which she teamed with a grey hoodie and black mid-calf socks with trainers.

Natalie chose to tag popular activewear brand Alo in her post.

The 30-year-old wore barely any makeup on her flawless skin and had her glossy blonde locks out.

This week Natalie revealed her private battle with scoliosis.

The beauty, who has shot campaigns for the likes of Guess in the US, said she was preparing for spinal fusion surgery.

'It's getting worse. It's going to continue to get worse,' she said during a Q&A on Instagram on Monday.

'I am constantly in a level of discomfort. There are days when I can't ignore it.'

Scoliosis is the sideways curvature of the spine. Natalie said her spine has moved '60 degrees' and that makes her a candidate for surgery.

The fashion star will undergo surgery in 15 days, with doctors 'removing her discs' to replace them with artificial ones and a brace.

'They are removing my discs, putting in fake ones and drilling a pole to my spine, so I am straight up and down again,' Natalie explained.

The operation will see her in hospital for one week and her recovery time is estimated to be about six weeks.

Natalie said she won't be able to work, but admitted that 'winter' is a much better time to undergo the procedure.

'I will be affected as I won't be able to work [for now,' she said.

'[But] timing wise, this is the perfect opportunity.'

Nat recently relocated back to Sydney with her Neighbours star boyfriend, Harley Bonner.

In November 2019, she revealed her excitement at having secured her dream job as the face of Guess' holiday campaign in the United States.

Natalie told The Daily Telegraph at the time that she believed being chosen as a Guess girl had 'a lot to do with her curvy body'.

'One of the biggest compliments I got on set was the clothes fit me so well,' she said.

'...and that was not because I was really thin, but because I was curvy and had a full figure. That's what being a Guess woman is all about.'