The fad for exercising on vibrating platforms which claim to multiply the fat-burning benefits of a traditional workout has raised concerns among experts.
They found no scientific basis for claims that the machines help people lose weight and, moreover, warned that incorrect use may cause dizziness and spinal damage, according to a Consumer Council report.
The council has referred its report to the Customs and Excise Department to see whether manufacturers have breached the Trade Descriptions Ordinance.
Amid adverts proclaiming "Vibrate away body fat", the council collected information from seven manufacturers and sought advice.
Physiotherapists said that the exercises manufacturers recommend to perform while standing on the machines would help weight loss but found no evidence that the vibration made them any more effective.
Chinese University sports science professor Stanley Hui Sai-chuen said that doing housework was more effective in burning calories. Any extra possible muscle activity caused by maintaining one's balance on the platforms would be mild, and at most would burn 10 grams of fat an hour, while an hour's housework burns 34 grams of fat, said Hui in the council's report.
The report warned that users must keep their knees bent, as standing up straight could transmit the vibrations to the head, causing dizziness. And sitting on the platforms could cause a disc protrusion in the lumbar spine, which can press on the spinal nerve and cause severe pain.
Also, lower vibration frequencies - under 20Hz - may cause organ damage as they vibrate at similar frequencies.
"Don't create your own postures and ways of using the machine, as that may damage your body," said council chief executive Gilly Wong Fung-han.
The council advised people to seek medical advice before using the machines.
"Hong Kong's manufacturers commonly make exaggerated claims in their promotions," said Professor Michael Hui King-man, chairman of the council's publicity and community relations committee.
"As for whether any of these machines' manufacturers have been lying, we're unable to reach a conclusion at this point."