A 15-year-old boy is in a critical condition in hospital after being found pinned to a weightlifting bench with a bar across his neck after trying to lift 100 kilograms in a Brisbane gym on Tuesday evening.

The ABC understands Ben Shaw was working out on the bench press, attempting to lift more than his body weight, at the Pine Rivers PCYC gym, north of Brisbane, when the weightlifting accident happened.

Ben was taken to the Lady Cilento Children's Hospital after the incident. ( Facebook: Ben Shaw )

But it was not until some time later that he was found by a staff member with the bar across his upper neck and throat, pinning him to the bench.

It is not clear how long he was trapped.

PCYC gym and fitness centre rules state that children under 16 years of age are not permitted to use weights equipment without proper supervision.

It also states members use the equipment at their own risk and management assumes no responsibility for any injury that may occur.

Ben was taken to the Lady Cilento Children's Hospital in a critical condition, and has family by his side.

Workplace Health and Safety is now investigating and will scrutinise CCTV footage to determine exactly what happened.

PCYC chief executive Phil Schultz said the organisation was cooperating fully with the investigation.

"At this stage at PCYC Queensland our focus and our thoughts are with the person in question," he said.

"This is a terrible incident and everyone here at PCYC Qld has been impacted by it.

"This kind of news is always extremely distressing.

"Our hearts go out to his family and friends and the wider community."

Pine Rivers PCYC remains closed.

Ben Shaw was trying to bench press about 100 kilograms when he became trapped. ( Facebook: Pine Rivers PCYC )

Gyms have duty of care, industry association says

Pine Rivers PCYC is a member of Fitness Australia, the peak industry association.

Ben Shaw, 15, was working out at the PCYC Pine Rivers gym when the accident happened. ( Facebook: Ben Shaw )

A Fitness Australia spokeswoman said the organisation would not be providing specific comment on the accident.

"We want to allow the relevant authorities to conduct their investigations, without our speculation," she said.

"All fitness businesses have a duty of care to prevent harm which could reasonably be expected to occur whilst a consumer is using the service provided by the business.

"Professional standards and guidelines developed by Fitness Australia assist fitness business members in mitigating risk and exercising duty of care.

"Our thoughts are with the young man and his family."