Raiders training with hypoxic elevation altitude masks- Josh McCrone.

PEAK FITNESS: Raiders players, including Josh McCrone, at left, try out the elevation training masks on Tuesday which are designed to increase breathing capacity. Photo: Melissa Adams

They look like military gas masks, a secret training device the Canberra Raiders hope will give them the edge when National Rugby League combat resumes this weekend.

The entire Raiders NRL squad has been training this week at a simulated altitude more than double the height of Australia's tallest peak, Mount Kosciuszko, without leaving their Bruce Headquarters.

The Raiders have been trialling a device - known as the Elevation Training Mask - which its inventors say provides resistance training for the lungs, increases breathing capacity and improves the body's use of oxygen. NRL clubs, including the Raiders, have long used simulated altitude devices, especially during the rehabilitation of injured players. But it's the way the Raiders have been experimenting with the devices this week that is more unique to team sports.

Raiders players have been strapping on the masks for their warm-ups and speed drills in the days before their season-opening clash with the North Queensland Cowboys in Townsville on Saturday.

Raiders strength and conditioning coach Nigel Ashley-Jones admitted it was a ''hunch'', but said he hoped it would enable players to drop the volume of their training in the lead-up to a match but still maintain high-intensity fitness levels.

''It's like breathing through a straw with your nose blocked,'' Ashley-Jones said of the masks, which have been set at a simulated altitude of more than 4500 metres above sea-level this week.

''They [altitude devices] were all the rage at one stage, but the way we're using it is a bit unique.

''We're trying to create science here, we've just got a hunch. Number one, it isn't going to harm them, worst-case scenario nothing happens. But best-case scenario we'll get a little bit of improvement. We believe it will make a difference.''

The Raiders have placed high expectations on fitness standards

this pre-season, with players asked to strip body-fat levels to record-low levels as they strive to reinvent themselves under new coach Ricky Stuart. The Raiders have enrolled players with sleeping issues into a scientific AIS sleep study to try and improve performance. They have also trialled with heat-exposure training, working through the hottest parts of the day during summer. ''The boys have been wearing their skins through the heat,'' Ashley-Jones said. ''We've been known as a cold-weather team, but we want to become an all-weather team.''

While altitude training in sport has been around since the 1960s, portable altitude devices are more innovative.

Australia's world champion ironman triathlete Pete Jacobs is an ambassador for the Elevation Training Mask, which cost about $100 a unit.

Professor Chris Gore, head of physiology at the AIS, specialises in altitude - or hypoxic training - and admitted research in team sports was not as extensive as it was with individuals.

''Some of the other footy teams like [AFL club] Collingwood go over to Colorado or Arizona and go up in the mountains but that's very expensive and very time consuming with all the travel time and lost training, so lots of people are looking at simulation devices,'' Professor Gore said. ''The jury's out in terms of performance benefits but I think I've worked with enough athletes to know there are small performance benefits, in the order of a couple of per cent. Athletes are all about the last one percenters. I think it works.''