Altitude is set to have an impact in the Denver Test but not in the way some had feared, with England playmaker Gareth Widdop suggesting it may be possible to kick a 60-metre penalty goal at Mile High Stadium on Saturday (Sunday, 6am AEST).
England and New Zealand had their first training sessions since arriving in the United States on Tuesday, and Widdop and Kiwis winger Jamayne Isaako noted that they could kick the ball further than usual because of the altitude.
The Denver Broncos, who are supporting and hosting the historic Test, boast the best home record in the NFL since 1975 and use the stadium's 1609m elevation to gain a psychological advantage over opponents.
The last thing visiting teams see as they leave the away dressing room, which will be used by England, is a giant sign painted on a wall opposite the locker room door, welcoming them to Denver, the "MILE HIGH CITY, ELEVATION 5280' ABOVE SEA LEVEL".
Before they take the field, they pass another sign warning of "HIGH ALTITUDE HAZARDS" and "ALTITUDE SICKNESS" – "regardless of fitness".
The England and New Zealand team medical staffs are confident this won't be an issue for their players as they have five days to acclimatise and none reported feeling any ill effects after their first training session.
However, Widdop said he expected the altitude to have an impact on goal kicking and kicking in general play if the kickers don't adapt.
"I had a few little kicks during the session and the ball travels a fair bit further so it will be interesting," Widdop said. "We will have to see how the game pans out but I have no doubt you could edge a goal over from 50m or 60m out with the altitude."
The longest field goal in NFL history - a 64-yard (58.5 metres) effort by Matt Prater - was kicked at Mile High Stadium. Three of the five longest field goals ever have been in Denver.
The longest punt in NFL history also occurred at Mile High Stadium when Steve O'Neal of the New York Jets kicked the ball 98 yards (89.6 metres) during a match in 1969.
It has been estimated that a kicked ball travels about 10 percent further in Denver than the same kick would at sea level.
"It felt like the ball floated a bit more because of the altitude," Isaako said. "I will back myself from anywhere I feel comfortable kicking the ball.
"I went out there today and had a little kick around to get a feel for what Denver and the altitude is all about and I felt pretty comfortable with my kicking."
There has never been an NRL match played at altitude but England players had a training camp in South Africa before the 2013 World Cup and were based at Potchefstroom, which is 1340m above sea level.
"I did some kicking there and it was a bit the same but we didn't play a game," Widdop said. "It is going to be interesting to see what difference it makes on Saturday."
To accommodate concerns raised by the RLPA and NRL clubs about the altitude and summer temperatures in Denver, there will be two-minute drinks breaks midway through each half of the Test.
The Kiwis narrowly avoided a hail storm before their training session at University of Denver Soccer Field.
The seven debutants in the New Zealand team and new coach Michael Maguire stripped down to their undies at the end of the session to perform a haka for the other members of the team – a tradition for newcomers to the Kiwis.
The promotion for the Test received a boost after South Sydney co-owner Russell Crowe indicated on Twitter that he would be travelling to Denver to watch Sam and Tom Burgess play for England.
The Test will be refereed by Super League match official Ben Thaler, with Englishman Chris Kendall and New Zealand’s Chris McMillan to be the touch judges.
NRL referee Jarred Maxwell will be the video referee.