Taking the example of our forbearers, a growing fitness movement across many countries encourages people to remain fit by making use of ancient movement skills, such as running through bushes barefoot.
Founded by a French trainer, Erwan Le Corre, about four years ago, it encourages natural, functional exercise in an outdoor setting. It also promotes a paleo-style diet, which is based on hunter-gatherer foods such as meat, vegetables, fruit and nuts, the Sydney Morning Herald reported.
About 250 people around the world have become official instructors since qualifications were introduced in May this year.
The method teaches practical movements based on how humans used to move in nature or childhood, said the instructor Vic Verdier, who runs public workshops all over the world.
These can be adapted for indoor and urban use but are preferably done in natural settings, where each workout is adjusted to a particular terrain. No special equipment is necessary, he said.
"What we try to do ... is relearn the way we used to live and move in general. It doesn't mean we want to live like cavemen or anything stupid like that. It just means we spend too much time sitting and too much time in an artificial environment and therefore most people just don't know how to move [any more," the paper quoted Verdier as saying.
Unlike most joggers and walkers, who prefer the safety and convenience of man-made tracks and padded soles, Brad Osborn, who has completed MovNat workshops in Australia and the US, enjoys scurrying through the bush, jumping over logs and crawling underneath branches.
"People think I'm crazy but the ability to connect to the earth ... and the capacity to run through any terrain barefoot is one of the things [this workout] gives you," the decathlete and volleyball coach said.
"Running through the bush engages every part of your body and mind because you have to be completely aware of every point of balance - it's shifting all the time," he added.
Tanya Carroll, a trainer from Livestrong Primal Fitness in Melbourne, said the method caters to every level of skill, from beginner to advanced, but there is no formal hierarchy. It engages people's imaginations, is not competitive and can be used to supplement other sports and exercises, she says.
Most of her clients fall into the 25- to 35-year-old age bracket, with just as many women as men showing interest.
The outdoor extremes in Australia can sometimes prove a challenge, however.
"Obviously that's something we have to be aware of. With our weather we have to be careful about exposure to the sun so it's not something I'd be doing in the middle of summer on a 40-degree day, but you work around that," she noted.
Others also warn that the system may not suit everybody. Chris Tzarimas, the director of the lifestyle clinic in the faculty of medicine at the University of NSW, compares it to commando-style training that is most likely to appeal to fit and able-bodied people.