The 22-year-old stands at 206 centimetres tall and now weighs 119 kilograms - "easily the heaviest" he has been - after taking advantage of an intense gym program in Wallabies camp.

Frost is the tallest player on the Brumbies roster and now find himself in the upper echelon of the club's heavyweights having added nine kilograms to his frame over the past year.

He has the national set-up to thank for it after being in camp with the Wallabies during the Rugby Championship, cashing in on extra gym sessions when he was not playing matches.

But now the challenge will be maintaining that extra muscle mass when he returns to action with the Brumbies during their Super Rugby Pacific campaign.

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"By the end of it, we were just trying to gym as much as possible because there was a group of us that just got in and did gym when we weren't playing games so we got a few extra sessions," Frost said.

"I put a few kilos on here and there but it's been enjoyable. It's easily the heaviest I've been but I need to be able to keep the weight and be able to run around with that.

"Naturally as a tall lock [you want] to put on mass and increase strength as well and obviously size will come with that. I'm a bit younger so I've got a bit of time to do it gradually and not all at once."

Frost has been widely touted as a Wallaby-in-waiting and his time in camp with Dave Rennie's squad this year will have been invaluable for his development.

Now he has returned to Canberra more critical of his own game as he searches for ways to help himself win that maiden Test cap.

"The higher you went up, the quicker the game. Training-wise, in the first couple of sessions [with the Wallabies] it was like 'jeez, this is quick'," Frost said.

"You were just constantly running. Once you got used to that and come back here, you see a bit of a change. I took a few different bits and pieces off other guys in technical work. It was good to ... [hear] different voices and opinions.

"You've got to be good yourself to be honest. It's no good telling someone they're no good or to improve things, and then you reflect on yourself and you weren't up to shape.

"It's made myself be a bit more critical around what I do. It's a pretty open environment [at Brumbies training] so I'm happy to be told off by other people, just for constructive criticism."

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