'Physically ill': Aussie young gun's sickening moment at Olympics

Australian sprinter Riley Day left commentators concerned for her welfare after going all out on the Tokyo heat to qualify for the 200m Olympics semi-final.

The 21-year-old Queenslander moved on to the semi-finals in a blistering time of 22.94 seconds, but she has promised more the races to come.

'WHAT A FREAK': Runner's 'mind-blowing' act after fall in 1500m

'WHAT THE HELL': Aussie runner caught in 'ridiculous' farce

This was despite the concern of Channel 7 commentator Bruce McAvaney, who suggested Day appeared 'physically ill' after her taxing heat in the heavy Tokyo sun.

Day required some time to recover from her race, hunching over in a shady area of the track and taking several moments to catch her breath.

Fellow commentator Tamsyn Manou said the high temperatures in Tokyo had clearly had an effect on Day as she waited for her heat to begin.

"She's in absolute pain because of the heat," she said.

"She's also been out there for a while, behind the blocks and I think the heat has probably taken a little bit out of her."

In her first Olympics, Day overcame some pre-race nerves to claim the third automatic qualifying spot in her opening-round heat on Monday morning.

Speaking to Channel 7 after the heat, Day said she was confident she could improve on her first outing.

"I was trying to just remember that it is just a race," she said.

"The Olympics isn't going to change how fit I am, how fast I am and how well I run.

"If anything it can make me lift even more, so I feel a lot more relaxed now that the first run is over.

"I know how everything works and I can just leave it all on the track tonight."

Sprint star savaged over 'unforgivable' act at Olympics

Manou and McAvaney have tore strips off Shericka Jackson after the Jamaican star eased up in the 200m heats at the Olympics and failed to make the semi-finals.

Jackson provided a major shock at the Tokyo Games on Monday when she failed to advance to the semi-finals in the 200m event.

The bronze medallist in the 100m last week behind compatriots Elaine Thompson-Herah and Shelly-Ann Fraser-Pryce, Jackson was tipped to medal again in the 200m.

But the Jamaican produced an extraordinarily lazy effort in Monday's heats, lumbering down the straight and easing up well before the finish line.

The bizarre tactics backfired spectacularly when she failed to qualify for the semis.

"You cannot do that at the Olympic Games," Aussie Olympian Manou said in commentary for Channel 7, calling Jackson "too cocky".

"That is unforgivable. I mean, she's not even trying,

"Look at her at the back of the field. It's good to have confidence in sport but that's just being a little bit too cocky".

McAvaney added: "Four one thousandths of a second would have got her through. I can't believe the unprofessional way she went about that race."

Jackson had the third-fastest 200m time this year, but has ruined Jamaica's hopes of completing a clean-sweep of the medals in both the 100m and 200m.

With AAP

Watch 'Mind Games', the new series from Yahoo Sport Australia exploring the often brutal mental toil elite athletes go through in pursuit of greatness:

Click here to sign up to our newsletter for all the latest and breaking stories from Australia and around the world.