The Denmark international has been put through his paces in Copenhagen in a bid to lose weight and get match fit after failing to seal a move away from north London in the summer
The 25-year-old spent much of the summer pushing for a move away from the north London club after falling out of favour with manager Arsene Wenger.
Bendtner – who has been out on loan at Sunderland and Juventus for the last two seasons – was close to joining Premier League new boys Crystal Palace on the final day of the transfer window, but a move failed to materialise as Arsenal were unable to bolster their own forward line.
Having played hardly any football last season because of injury, the Denmark international is desperate to regain match fitness, and personal trainer Thomas Jorgensen admits he needs to lose some weight.
"He needs more fitness and has had a few problems, but it is not as if he needs to lose 20 kilograms," Jorgensen said.
Arsenal's striker shortage has ensured Bendtner of a place in their 25-man Premier League squad, and last week Bendtner declared he would continue to do his best for the club.