"And you start off simulating it, but it becomes real because where are other people around also laughing - it's infectious and always turns into real laughter."

Laughter yoga combines laughter with yogic breathing exercises to provide one-hour workout sessions that include 30 minutes of laughter.

Mr Robertson says the main aspect laughter yoga shares with traditional forms of yoga is the focus on the breath - laughter makes people breathe more deeply, which has a raft of benefits in itself.

"As a psychologist, that's the first I would get people to do," Mr Robertson says.

"Get people to breathe more deeply, get more oxygen to the brain, help them relax."

Laughter yoga advocates say it exercises the heart, diaphragm, abdominal, intercostal, respiratory and facial muscles, with 20 minutes providing a workout equivalent to 10 minutes on an exercise bike.

Among other things, it strengthens facial muscles and reduces wrinkles, leaving people looking younger, improves cardiovascular health, reduces blood pressure, boosts body's oxygen and energy levels, as well as immune cells that attack cancer, infection and viruses.

It releases endorphins, a natural pain killer, stimulates the lymphatic system and boosts the immune system, and reduces levels of stress poisons 50 per cent or more in minutes.

And the positive effects came at no cost, Mr Robertson says.

"There are no side effects - it's not medication, not talking therapy.

"We just leave our minds at the door and engage on what is a cardiovascular workout.''

The classes are free - laughter should always be free, Mr Robertson says.

He envisages the therapy moving beyond the community centre where he holds his classes.

"It needs to grow in all the places where laughter is missing - old people's homes, organisations, hospitals, that sort of stuff."

Laughter yoga began with a group of five in Bombay, in 1995, and has now spread to 5000 clubs in 53 countries.

Dr Madan Kataria, an Indian medical doctor dubbed the Guru of Giggling, started the groups with his wife after becoming interested in the health benefits of laughing while writing an article on it for a medical magazine.

Speaking from South Africa, Dr Kataria said when he started, very few people laughed in the big sprawling city.

Life was "very stressful" in Mumbai, he said.

"We started out by telling jokes, but after about 10 days, we ran out of jokes," he said.

"So we said, let's laugh without jokes."

Now, 12 years later, Dr Kataria says he doesn't remember the last time he had a cold.

(chinadaily.com.cn March 20, 2007)