It's been excruciatingly hot in South Bend, Indiana, where the Wallabies have been preparing before their match against the USA Eagles at Chicago's Soldier Field on Saturday night (9.40am Sunday (AEST).

The question is whether the slow-roasted Wallabies are going to be over-cooked at the Rugby World Cup, the marathon tournament beginning in England on September 18.

There remains a game to be played before then and assuming Australia safely navigates the improving Americans, they can turn their full attention to the pool stages of the World Cup, which includes meetings with heavyweights England and Wales.

Head coach Michael Cheika and his staff have put the squad through the ringer physically since day one of their camp on the Sunshine Coast back in July. Sessions have been torrid and confrontational, occasionally spilling blood and igniting tempers.

That intensity continued throughout The Rugby Championship and even the day before they left for America, where players were sent to do hill sprints the morning after the John Eales Medal presentation dinner at Randwick.

A number of players told Fairfax Media that they didn't have much left in the tank by that stage and were looking forward to getting on the plane to the US, where they have been in camp at Notre Dame University, the home of the storied Fighting Irish athletic program.

But Ben McCalman, who will vice-captain the Wallabies at Soldier Field, said he didn't believe the training regime but been overdone and the players all believed there was method to the punishing routines.

The style of training under Cheika was somewhat of a wake-up call to those not familiar with his methods – one of which is to join his men on the park and rip in during contact drills – but McCalman said everyone had adjusted and adapted.

"You become used to it. We had an opportunity over the past couple of weeks when there wasn't a game, so you could afford to be fatigued come the weekend when there was no expectation to run out and play," McCalman said.

"It's very smart. There's a lot of reasoning behind the training that Cheika and the team employ.

"He picks his times when we can work extra hard and get some gains. We did that before we left and we continued to do that early this week."

Cheika has demanded his players train under pressure situations, even revealing he'd called a session short in Sydney when players weren't hitting the required notes.

McCalman said the players were hoping the pay-off for all of the grind would eventuate in the World Cup, possibly in a scenario where the Wallabies can draw on their fitness and detailed preparation late in a game.

"I'm holding up pretty well. I think you will see it [the rewards]. There might be times when you are fatigued during or after training but there is a real belief there is going to be a reward at the end of it. We all know what that could potentially be," McCalman said.

"It gets everyone closer and I think just having that extra time will be very beneficial. I've gained so much respect for the bigger blokes. Seeing Will Skelton and the tight five, the big men working so hard, it's inspiring and there's no excuse for us more mobile players."

McCalman said there had been plenty of curious onlookers around campus, with most interested on how the Wallabies could possible compete without the layers of protective equipment used in American football.

On the other side of the coin, the Western Force backrower said he has no idea how the college team stays upright carrying all of the pads given the summery weather.

"Everyone seems to be very interested as to how we play with no helmets or shoulder pads on. I actually don't know how they do it running around in that heat. But there has been a lot of interest and hopefully there's a great turn-out on Saturday."