New Zealand players had nerve stimulators on their legs during the flight to Denver and have been told not to wear sunglasses while in the Colorado city to help them adapt quicker to the time difference before their Test against England.

The Kiwis arrived in Denver 18 hours after departing Sydney on Monday and players said they were ready to start training after New Zealand doctor Greg McLeod and the team’s high-performance staff implemented a number of measures to assist their preparation for the match on Saturday (Sunday, 6am AEST).

Among the requirements for the Kiwis players on the flight were regulated sleeping times, drinking five 800ml bottles of water each and taking a course of probiotics and melatonin.

The Kiwis also wore oxygen masks to avoid germs circulating on the plane, used nasal sprays because of the dry air and had nerve stimulators on their legs to maintain blood flow.

"The planning for this trip started well before we arrived into camp last weekend, having a good look at Denver, having a good look at our flight plans and those sort of things to get our hydration plans right," McLeod said.

"We had a look at some very specific things around immunity support to make sure guys didn’t pick up viruses, not only that they didn’t get sick on the way but that they arrived healthy and ready to play.

"With circulation, we had a number of measures around that and not just the usual compression and hydration stuff but we had some other tricks up our sleeve to ensure that even when the guys weren’t moving around the blood was still circulating.

"Basically, what the guys had were nerve stimulators. There is a mechanical pump and it contracts the muscles which maintains blood flow."

Kiwis back Dallin Watene-Zelezniak said the players felt like they had been "treated like kings" with the preparation for their trip to the United States.

"The doctor gave us times that we needed to sleep, times we needed to eat, the water we needed to drink, and all the boxes have been ticked," Watene-Zelezniak said.

Before leaving Sydney, the NZRL booked a mobile cryotherapy van for the players to use on Sunday night and they slept on sky beds in business class.

Upon their arrival in Denver, the Kiwis players had massages booked and were told not to wear sunglasses while in the city to help them cope better with the effects of jet lag.

"The reason jet lag is a thing is because it is hormones that have gotten out of balance," McLeod said. "Melatonin is a specific hormone that is regulated by light so basically when the sun goes down the melatonin comes up and when the sun comes up the melatonin goes down.

"Therefore, when the guys go out for the next few days, just walking around or whatever, they should have no sunglasses to maximise the sun."

Each New Zealand player was given a medical assessment by McLeod before being cleared to travel to Denver and the GPS data from their training and Saturday’s Test will be forwarded to their NRL clubs.

The Kiwis are in camp and Michael Maguire has named his Squad to face England next weekend in the Denver, CO #TeIwiKiwi 🇳🇿 pic.twitter.com/eucgagDe9s — NZ Rugby League (@NZRL_Kiwis) June 17, 2018

New Kiwis coach Michael Maguire took South Sydney to England for the World Club Challenge and also the Flagstaff in Arizona for an altitude training camp and he said the team couldn’t be better prepared.

"I’ve been fortunate to travel overseas a number of times with teams and I have been very impressed by what has been put in place by Greg and the performance staff of Don Singe and Shaun Edwards and others," Maguire said.

"I think that they have ticked off on everything that is required, from timings of sleep, nutrition and just different things to help make sure you get the right recovery."

The Kiwis will have their first training session under Maguire at the University of Denver on Tuesday afternoon. England will train there earlier.

Meanwhile, England have lost halfback George Williams after he was ruled out with a knee injury suffered in Wigan’s defeat of Hull FC last Saturday.

Williams still travelled to Denver in the hope of being fit, but was ruled out by England's medical staff.

His absence means England coach Wayne Bennett will almost certainly start with St George Illawarra five-eighth Gareth Widdop and St Helens utility Jonny Lomax as his halves, with Warrington’s Stefan Ratchford at fullback.