All Blacks trainer Nic Gill lifts lid on the fittest players in New Zealand

All Blacks trainer Nic Gill has revealed that the three Barrett brothers - Beauden, Jordie and Scott - are among the fittest players in New Zealand.

The trio of siblings were all named by Gill as among the nationwide leaders for the gruelling Bronco fitness test.

The drill, which is used as a measurement of aerobic endurance, sees players run shuttles of 20 metres, 40 metres and 60 metres five times over as quickly as possible.

In an interview with Stuff, Gill said Beauden and Jordie, along with Chiefs playmaker Damian McKenzie, were the three fittest backs in the country.

Scott, meanwhile, joined Crusaders hooker Codie Taylor and Blues loose forward Tom Robinson as the best of the forwards.

Robinson, who has missed most of the Super Rugby Aotearoa campaign after sustaining a knee injury in his side's opening game against the Hurricanes in June, is the only one of the six players yet to feature for the All Blacks.

However, Gill has been keeping track of the utility forward's - who is capable of playing lock and blindside flanker - fitness records as he looms as a potential call-up to the national squad.

Beauden made headlines a month before the Kiwi domestic league kicked off for setting a Blues club record for the fastest Bronco time, setting a rapid pace of four minutes at 12 seconds.

By comparison, former All Blacks captain Richie McCaw’s best time in the 1.2km test was four minutes 56 seconds, according to rugbysmart.co.nz.

Gill, however, noted that there wasn't a huge emphasis on raking up running mileage throughout a week of training.

“In a game a Beauden Barrett, if he's playing fullback, might cover 8km.

“Maybe on Monday he might do 4km, Tuesday another 8km, and then Wednesday have a breather, Thursday another 6km and Friday 4km before 8km during the game.

“For the forwards, probably 15km-20km in terms of total distance ... some of that is running fast, and some of that is jogging slow.”

Gill said the amount of running decreases as the size of players get bigger, but that didn't stop him for lauding the fitness feats of those in the tight five, reserving special praise for in-form Blues captain Patrick Tuipulotu.

“Even just getting up and down off the ground, it's pretty impressive what some of these big guys can do,” Gill told Stuff.

“Patrick [Tuipulotu] has maintained his condition really well this year.

“He’s 126kg-127kg, playing 80 minutes, getting to his feet quickly, he’s trucking the ball up, he’s making big hits."

Gill said that since he first joined the All Blacks staff 12 years ago, the size of front rowers and locks have increased, on average, by 15 to 20kg.

“Back in the day Ben Franks was 112kg as a prop, but if we were to average the top four props in the country right now, they'd average 127kg," he said.