Anti-gravity yoga which requires you to move acrobatically, often in mid-air, with the help of hammocks made from parachute silk, has become the latest fitness craze in US.

Anti-gravity Yoga improves blood flow to the thyroid and pituitary glands, which is believed to boost hormone function.

It is the brainchild of American choreographer Christopher Harrison, co-founder of Cirque du Soleil, the Daily Mail reported.

"The hammock is so supportive that almost anyone can try more difficult poses, such as turning upside down, without risk," said Gillian Reeves, National Group Exercise Manager at Virgin Active.

"Doing this means that muscles are worked in unfamiliar ways so that they become more evenly toned," Reeves said.

The warm-up includes looping your arms around the swathes of fabric and leaning backwards.

People hold on to the hammocks for balance while standing on one leg and buttocks clenched. Eventually, both feet are placed in the hammock and arms on the floor in a position called 'a plank'.

The inversion is introduced after a few moves. Easing the bottom on to the hammock, people lean backwards, and then carefully wrap their legs around the silk, turning upside down.

The scary bit is letting go, but the sensation of dangling from the ceiling is exhilarating. Effectively you have the weight of a bowling ball – your head – pulling your spine downwards, the paper said.

"Blood and nutrients are able to flow freely around the spine," Reeves said.