Germany hopes to grow its armed forces, winning tens of thousands of new volunteers -- a tough task in a country where many young people view military service with scepticism.

To find new recruits, the Bundeswehr must rely on the power of persuasion, and sees the FIBO fair -- a celebration of bulging muscles and displays of sweaty stamina -- as a natural venue to win the soldiers of tomorrow.

"The target group is right here -- we rely on young, athletic, motivated people to join the service," the 30-year-old lieutenant commanding the booth, who gave his name only as Peter, told AFP.

"We can approach them very effectively here."

Franz, a 31-year-old physiotherapist who declined to give his last name, set the day's record in the army booth's gas-masked fitness challenge, working his way through 50 jumping jacks, 20 squats, 10 press-ups and five burpees in just 46 seconds.

Shortly after, he told AFP that he would be open to joining the army in coming years: "Being there to defend my country is definitely an option."

Chancellor Friedrich Merz has called for Germany to become Europe's leading conventional military power, part of a broader rearmament push by European NATO allies to deter a hostile Russia.

By 2035, Berlin has committed to increase its troop strength to 260,000 soldiers -- up from the current 185,000 -- and boost the reserves to another 200,000.

To achieve this, Berlin introduced a system this year to register 18-year-olds to identify potential new recruits -- but so far has refrained from bringing back mandatory military service, which was suspended in 2011.

Conscription is a sensitive subject in Germany, which has a strong pacificist streak often attributed to the horrors of the Nazi regime, and so the Bundeswehr is looking for other ways to win hearts, minds and recruits.

- Obstacle courses, combat sports -

The Bundeswehr stand at the fair dominated the middle of two bustling aisles packed with young men in athletic shorts and young women in leggings and sports bras.

Helping draw attention to the troops was an imposing Fennek armoured reconnaissance vehicle and a troop transporter, parked on either side of the booth.

"We've expanded even further compared to last year due to the success of our recruitment drive at FIBO," the lieutenant told AFP at the big stand, which was manned by 92 soldiers and staff.

With obstacle courses, combat demonstrations and daily raffles offering prizes like water bottles, mugs, T-shirts and backpacks -- all in military shades of sand and khaki -- the Bundeswehr is pulling out all the stops to attract new soldiers.

A banner advertised an upcoming "Olympix" event at the Bundeswehr's sports school in the western town of Warendorf, where young people aged 16 to 19 can compete in football, beach volleyball and combat sports.

"We've become more professional and more attractive" to potential recruits, Peter said of Germany's military, although he declined to provide specific recruiting figures from the FIBO stand.

Potential recruits often "need three or four contacts before deciding to pursue a career path or change professions," he added, comparing the decision-making process for signing up to making a major purchase.

Linda Reinhard -- a 33-year-old physiotherapist who had just completed a combat course at the training stand while wearing a 13-kilogramme (29-pound) vest -- said she thought the public perception of the Bundeswehr had improved in recent years.

"With everything that's happening in the world, the guys and girls here really contribute to making us feel safe," she said, although she is not considering putting on a uniform at the moment.

"I have a great job, I'm very happy, but I think they need good people here they can rely on," Reinhard said, adding that she was keeping an open mind to one day doing military service.

"Maybe that would be an alternative sometime in the future, why not?"