Image caption Mr Xiao's book on paida lajin is sold in bookshops in Asia and has sparked copycats

A Chinese therapist who has come up with a "self-healing" philosophy involving slapping is at the centre of controversy in Australia.

Xiao Hongchi promotes the paida lajin method, which sees patients being slapped or slapping themselves repeatedly.

He has been questioned by police investigating the unexplained death of a seven-year-old Sydney boy who had earlier been taken to one of his workshops.

What does the process involve?

Paida involves patting ("pai" in Chinese) and slapping ("da") one's skin while lajin involves assuming various postures to stretch one's muscles.

Image caption Xiao Hongchi's books includes details of how to pat and slap joints, armpits, head, and shoulders

Participants vigorously slap various parts of their body, particularly joint areas and the head, until their skin turns red or starts looking bruised, as this video of a 2012 workshop in Malaysia led by Mr Xiao shows.

Some can go on to do stretches while lying down on tables or on the floor, against walls, or against doorframes.

Paida and lajin are linked to a concept in traditional Chinese medicine known as "sha", the belief that blood can be "poisoned" by toxins and needs to be expelled.

Practitioners believe paida and lajin improve blood circulation and draw out "sha".

Mr Xiao claims that when "sha" appears, it is an indication of "latent diseases".

Critics say this only results in broken blood vessels and bruising of the skin.

The BBC's Pamela Koh once underwent a beating therapy to treat a knee injury

I sat on a short stool facing the healer, a middle-aged Chinese man brandishing a bundle of hard rattan and bamboo.

He felt around my knee for where he thought the "little clots" were and without warning, forcefully whacked my knee. He aimed for exactly the same spot each time. It was excruciating. I yelled in surprise. The bruises turned purple quickly and minutes later, I had to halt the blows.

The beating needed to continue for at least 20 minutes to be effective, I was told. I gritted my teeth between the sharp, swift blows but I had to tell him to stop. He resumed until it became unbearable again and I tried to sit through the full 20 minutes of pain.

The bruises took weeks to heal. I am unsure if the knee healed from being "beaten" with a bamboo stick or if the body naturally heals itself over time. It certainly, however, is not for the faint-hearted and even though the knee got better, I would not go back in a hurry.

How popular is it?

The concept of "sha" is a widely-held belief in Chinese culture, and paida lajin has attracted a significant following in Chinese communities around Asia.

It is not uncommon for Mr Xiao's clinics to be sold out and attended by hundreds. A ticket can cost hundreds of pounds.

He first shot to fame when he published a book in 2009 entitled The World of Medicine: The Paida Lajin Self-Healing Method.

He has gone on Taiwanese talkshows to promote paida lajin, and has conducted workshops in China, Hong Kong, Taiwan, Malaysia and Singapore.

In recent years he has gone further afield to India, the US, Germany and Australia to hold clinics.

What's the controversy?

Mr Xiao's method have been heavily criticised as having no scientific or medical basis, and many have taken him to task for his claims that paida lajin can cure or ease the symptoms of a wide range of illnesses.

These include colds, body pains, Alzheimer's, strokes, paralysis, kidney failure and even cancer and autism.

For example, Mr Xiao recommends getting autistic children to engage in "group slapping games" and hit one another on their limbs, head, hands and feet.

"Do not panic seeing colourful patches of sha, lumps and swelling at the slapped areas. These are good healing reactions," his site states.

His site also carries testimonials from parents claiming they had slapped their children - including infants - and healed them of fevers, bronchitis and stomach flu.

Image copyright Getty Images Image caption Paida lajin practitioners believe bruises are manifestations of "sha", or poisoned blood

In April 2011, Taiwanese authorities fined him NT$50,000 (£1,060, $1,600) for "promoting folk remedies as medically effective", after he claimed that diabetic patients did not need medication and could be cured with paida lajin.

Aidan Fenton, the boy who died in Sydney, had type 1 diabetes and police believe he may have stopped taking insulin.

Several print and television outlets in China and Taiwan have run pieces questioning and debunking Ms Xiao's method, and have argued that his method is not part of traditional Chinese medicine.

But his followers swear paida lajin works, and have continued to practise it. Mr Xiao has even inspired copycats, with other authors writing books with titles like Patting and Slapping to Good Health.