Police said Dylan Voller, whose mistreatment in juvenile detention triggered a national inquiry, tied part of his T-shirt around his neck and was gasping for air before he was cut free.
Voller, 21, was one of five activists who were arrested during Friday's confrontation with a heavy police presence, the latest in a series of protests during the Games.
"(Police) found that the individual had actually torn part of his T-shirt and tied it around his neck and tied a knot and appeared to be grasping for air and choking as a result of that," police assistant commissioner Brian Codd said.
Police stopped the van and used a penknife to cut through the material, Codd said. Voller received medical attention under police custody but is not in a serious condition.
"My fear is that if they hadn't of done that we could have had a very, very serious outcome," Codd said.
Voller and four others were arrested after dozens of indigenous activists attempted to disrupt a live TV broadcast on a beach at Gold Coast, the Games' host city.
They chanted "No Games, no justice!" as they were blocked by a heavy police presence who stopped them marching to the scene of the TV broadcast.
Protesters who have dubbed the event the "Stolenwealth Games" have staged a number of demonstrations including at the opening ceremony, where three people were arrested in clashes with police.
The treatment of Voller became the focus of public outrage after footage was broadcast of prison guards assaulting mostly indigenous boys in the Northern Territory, including stripping them naked and using tear gas.
Images released in 2015 showed Voller, then 17, hooded and shackled to a mechanical restraint chair and left alone for two hours.
It prompted a Royal Commission into treatment of children in detention, which last year made multiple recommendations, including the immediate closure of the Don Dale detention centre in which Voller was held.
Aboriginal culture stretches back tens of thousands of years but indigenous people are now the most disadvantaged in Australia, with higher rates of poverty, ill-health and imprisonment than any other community.
Eyewitness? Submit your stories now via social or:
Email: eyewitness@pulse.ng
![The woman was recorded, among others, while bathing [BI]](data:image/svg+xml;charset=utf8,%3Csvg%20xmlns%3D'http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg'%20width%3D'300'%20height%3D'172'%20data-ring-placeholder%3D'1'%3E%3C%2Fsvg%3E "The woman was recorded, among others, while bathing [BI]")
