A renowned gym junkie, injury-plagued AFL defender Marcus Adams has been stunning his Brisbane teammates with improved running endurance.

If early indications are anything to go by, the former Western Bulldogs player could be in for his most dominant AFL season yet.

Adams missed more than half of his first year at the Lions with a knee injury, before playing an important role in the club’s first finals appearance in 10 years.

The big-bodied defender has returned to training in top shape as he seeks to build on his partnership with All-Australian Harris Andrews in Brisbane’s back six.

He was second in the Lions’ recent 3km time-trial, finishing just behind young midfielder Jarrod Berry who has won the past four.

Adams even pipped captain Dayne Zorko and wingman Hugh McLuggage.

“All of a sudden on the seventh lap, big lumberjack (Adams) behind me is cruising along,” Berry said.

“I was a bit surprised on that but he was really impressive.

“He’s one of the most professional blokes that I’ve come across in terms of looking after his body, eating well, hydrating and doing his weights.

“He’s a monster in the gym…he’s just got that real good basis of running, and on top of that, he’s just a natural athlete.”

Berry said there was fierce determination within the Lions for spots after they were last year’s big improvers, rising from 15th in 2018 to playing in two unsuccessful finals games.

“Everyone’s pushing each other; there’s no point me resting on my laurels and letting blokes catch up to me,” Berry said.

“It’s really healthy at the moment, those competitions, and it only gets more ramped up in actual match practice.”