She has been retired for more than seven years, has a hectic life as a mum of three and is not as "fit and fast" as she used to be, but Kim Clijsters believes she will still be competitive on her return to tennis.

The former world number one, 36, is making her comeback in March after a knee injury put the brakes on plans to return at next week's Australian Open.

In a wide-ranging interview with BBC Sport, she explains what motivated her to take to the court once again, which players she is looking forward to facing and what she makes of the air quality issues the players are facing at the Australian Open.

She says a lot has changed while she has been away - but can she still do the splits?

'I would be vocal' on air quality issue

The media day at her academy in her hometown of Bree in Belgium was supposed to be all about the four-time Grand Slam champion's much-anticipated return to tennis, but Clijsters inevitably found herself being asked about the air quality issues in Melbourne, where qualifying has been delayed because of poor air quality due to bushfires and players have had breathing problems.

Clijsters says if she was at the Australian Open she would be "vocal" in getting organisers to explain how they are going to deal with the issue when the main draw starts on Monday.

"If it's not possible to play in then what's the point?" she said.

"If you can't play and bring good tennis and be fit enough to play two hours, or even the guys 4-5 hours in this environment. You can't avoid or ignore it.

"They have delayed matches but it's not going to solve the air quality. On the centre and show courts there is not an issue - they can close the roof and they can have the ventilation on but on the outside courts… you can't play a whole event just on a few show courts that have a roof.

"If I would have been there I think I would have been very vocal and at least talk to the board and the tournament directors to try to think about solutions."

She said some of the players from her academy are involved in the qualifying event and have been talking about how hard it has been.

They feel the struggles at night, the coughing," Clijsters said. "It's a tough situation to be in. It's something that's out of anyone's control. It's important that players stay healthy."

She praised player efforts to raise money for the relief fund to help the crisis, in which at least 28 people have died and an estimated 10 million hectares (100,000 sq km) of land has burned since 1 July.

"Tennis is a sport that has always come together very well to try and make money for [disasters]," said Clijsters, speaking hours after tennis greats Roger Federer and Rafael Nadal were among a number of players to feature in a charity match for the bushfire appeal.

"Everybody cares about it, they all love the Australian Open, we just have to make sure that the people stay safe and healthy."

What made Clijsters come out of retirement (again!)?

Clijsters, who first retired in 2007 at the age of 23 to start a family, hung up her racquet for a second time in 2012 and has since thrown herself into being a busy mum as well as working as a TV pundit and playing at various Legends events.

But while she commentated on players like Serena Williams, who is still winning titles at the age of 38, she had a nagging feeling that she might not quite be done.

"Whenever I went to a couple of tournaments, even if I was doing commentating or if I was playing some legends, at the back of my mind at times I still felt I could still be a player - I'm not saying win Grand Slams, but be a player and not be among the legends or not doing commentary - still being competitive," she said.

"Then I would come home and be in craziness of the hectic life with kids and be like 'yeah, it's not possible'."

That was until her youngest son started school.

"I thought this will maybe give me some time and maybe I should just see how far my body can go and just go from there," she said.

"Maybe this can lead to coming back or playing a few tournaments a year, see how I will react. It very easily could have gone the other way."

The other key element was the rule that as a former world number one, Clijsters is eligible for unlimited wildcards at WTA tournaments. And there is no prescribed number of events that she has to play at.

"If they told me I had to play 16 tournaments a year and I have to go here, here and here, I would have said it was impossible to combine it but in this situation I can combine it," she said.

She is due to make her comeback in March and has wildcards for the events in Monterrey, Indian Wells, and Charleston.

Asked if anyone had tried to talk her out of returning, she laughed: "At least not to my face, behind my back maybe a little bit."

How will she fare against the new generation?

Clijsters, who won 41 WTA titles and spent 20 weeks as world number one, has not set herself - publicly - any goals for her comeback in terms of rankings or results.

But she is looking forward to mixing with a new generation of players, who she has been observing from afar.

"Simona Halep is not a young player but is someone I've never played against - the way she played against Serena [Williams] in that Wimbledon final [last year] was incredible to watch," she said.

"Bianca Andreescu - what she did at the US Open [when she beat Williams in the 2019 final]. Naomi Osaka is a player I enjoy watching - not just on the court but her press conferences. [American 15-year-old] Coco Gauff is definitely a girl I have my eyes on, especially in the big events. Fun girls, interesting."

It is not just the players who have changed since she played her last competitive match at the 2012 US Open.

"There is more and more science behind things these days, for my trainer and my osteopath - they also look at treatments differently. There is the cold therapies, so many new approaches to help," she said.

"I've been trying to go more - not fully vegan - but trying to be more healthy. You look at food that triggers inflammation differently. [But] there are things that haven't changed - I was a big believer in deep tissue massage back in the day - and I still do that."

Can she still do the splits?

Clijsters was always well known for her agility on court - often doing the splits when trying to get to shots. Unsurprising, perhaps, given that her mother was a gymnast.

And it sounds like we can expect to see some more.

"A few weeks ago when I was on training camp I did [the splits] out of the blue. Everybody on the sideline stopped and was kind of like 'why did you do that?', I was like 'sorry, I don't know, how it happened'," she smiled.

"I should be able to, just make sure I'm fit enough to get back up again with no pulled muscles."

Despite her return already being postponed because of a knee injury, she has not been put off by the physical pressures.

"The knee was an out-of-the-blue bad luck thing. If you put in the time, and you look at everything around you - the diet, the sleep, then you are capable of doing a lot of things," she said.

"If I do all that - I'm not saying I'm going to be as fit and as fast and do the splits like I used to do - I do think I'm capable of getting to a certain level that I feel happy with. It doesn't have to be a contender for a Grand Slam but to put myself for a level where I'm happy - that's the goal."

But before all that, though, she tells us she needs to take her daughter to basketball practice.

"But I like that, it's my life."