Australia’s Jillaroos were caught on camera using balloons in truly bizarre scenes in their locker room before their match against England’s Lionesses in Las Vegas.

The Jillaroos delivered a masterclass on Sunday, smashing the Lionesses 90-4 at Allegiant Stadium in a record-breaking match.

However, before the game, the Jillaroos were filmed in their rooms inhaling and exhaling from large balloons.

Walsh, who on occasions sleeps with tape over his mouth and wears nasal strips to maximise oxygen flow, has embraced various breathing techniques.

One of the most recent is known as ‘box breathing’, where a person exhales, inhales and then holds their breath at regular intervals.

The Jillaroos trounced England 90-4 in Las Vegas on Sunday

The Jillaroos were filmed in their locker room inhaling and exhaling from large balloons before the match

The method is used by US Navy SEALS to help them to remain calm and alert in pressure-cooker situations.

‘The best athletes in the world are all doing a thing called box breathing which is something we spoke about (at the Broncos) when we went in camp,’ Walsh told AAP.

‘It’s something I am getting into.

‘For me it is all about maximising my full potential and trying to find stuff that works. You don’t know unless you know, if you get what I mean. So you just dive in and have a crack.

‘I have a nose strip which just opens up your nasal passages and allows you to breath better.’

In Australia’s third-biggest win of all time, Tamika Upton scored five tries and set another up two in a complete domination at Allegiant Stadium

Winger Julia Robinson and bench centre Jess Sergis also crossed for hat-tricks for Australia, while Taryn Aiken was superb at halfback with six assists.

So dominant were the Jillaroos that they ran in 17 tries in the 70-minute fixture to claim their largest victory margin over a tier-one nation.

The Jillaroos that they ran in an astonishing 17 tries in the 70-minute fixture

Superstar Tamika Upton (not pictured) played a huge role, scoring an amazing five tries

The win was briefly marred by a horror head-on collision from the first tackle after the break, leaving England prop Vicky Whitfield prone on the ground.

After taking the hit up from the kick off, Whitfield clashed heads with Jillaroos front-rower Sarah Togatuki and both reeled from the collision.

Togatuki was taken for the field with a concussion, while Whitfield was eventually taken off on a stretcher on the back of a medicab. The 30-year-old was taken to hospital for precautionary scans.

Still, the main question for the NRL is whether the Jillaroos’ walloping of England is the best advertisement for the women’s game in the US market.

With no fully-professional women’s rugby or NFL competition in America, the NRLW is viewed as a space where rugby league can make an impact.

But Australia’s win was overwhelmingly one-sided.

England conceded tries in four straight sets at different stages in both halves, and scored their only points on the full-time siren through Georgia Roache.

By contrast, Pacific Championship matches between Australia and New Zealand have been far more competitive in recent years, leaving the Kiwi Ferns as a potentially better opponent for the Jillaroos next year.

Women’s State of Origin is also viewed as a potential way to sell the game in the US, with last year’s three-game series a compelling contest.

Regardless, Australia were ruthless against the Lionesses.

Upton was in everything, putting Jakiya Whitfeld into a gap in the lead up to the Jillaroos’ first try before scoring three more herself in the opening half.

Isabelle Kelly was dominant at left centre, scoring twice and laying on a nice try for Upton when she swept out wide and passed back inside for her fullback.

Prop Shannon Mato ran close to 200 metres, while Olivia Kernick laid on two tries in the second row in her first Jillaroos game since her controversial axing last year.