Natalie Fuller is one of an increasing number of people who are leaving gyms to keep fit with strangers outdoors - all organised through social media.
She said having a personal trainer was ''costing me a fortune,'' so she signed up for the free Sydney Fitness Boot Camp group at Hyde Park.
Why would people pay when they could do the same for free or a lot less?
She signed up online and had her request approved by the group's organiser before joining the regular Wednesday night session. The sessions are so popular the group's trainer, Ben Winegarden, often has to turn people away.
Mr Winegarden, who works in banking, is not a trained fitness instructor and admits he "wasn't even really into fitness" when the group's founder moved overseas and handed the reins over to him.
He studies YouTube clips and fitness sites in order to keep the workout fresh and challenging, and has seen a huge improvement in his own fitness: "I have to make sure that I'm in better shape than everyone else," he said.
Boot camp is just one of the free fitness options that people are getting into through the internet. Yoga, bushwalking, ocean swimming, football, dancing, beach volleyball, and even power walking are on offer from various social media sites.
Jelle Marechal is the founder of facetime.com.au, which has almost 90,000 members, although he estimates only 5000 of these regularly attend events.
He said the main appeal is the social interaction and that most of the events are free: ''You've got all those fashionable initiatives like boot camp, and you walk past the park and people are going crazy with their boxing. And I have thought, why would people pay when they could do the same for free or a lot less?''
Several months ago, Nadia Samperi and her husband, Daniel Adabow, joined a free football club, playing at parks around Sydney each Saturday afternoon.
"I've always thought gyms were a bit sterile,'' she said. ''But the soccer is outdoors, it's really fun and people are friendly. And it's free!"