A woman has been injured after a man somersaulted off a stage and into the crowd at a Northbridge festival venue on Monday night.

The man launched himself off the stage at Ice Cream Factory during a set by Australian band Peking Duk.

He landed on a 23-year-old woman, hitting her in the face and knocking her unconscious.

Ice Cream Factory said the man wasn't authorised to be on stage and that once he realised he had hurt someone, was devastated and offered cover any medical bills.

The 23-year old was treated at the outdoor venue by paramedics.

"Human bodies are not designed to take that sort of trauma,” Australian Medical Association President Andrew Miller told 7News.

"If you've got a 60, 70 or 80 kilogram man land on your head - that can break your neck, that can paralyse you and can turn you into a quadriplegic,” he said.

“It's a very risky thing to do."