A guffaw, a snicker, a belly laugh - they're all part of a health trend that started in India more than 12 years ago and one that a group of senior citizens in New York City have adopted to help them stay in mental and physical shape. It's called laughing yoga. "Well, laughing yoga is based on yogic principles, it involves laughter exercises, some improvisation, some chanting 'ho, ho, ha, ha, ha' and some deep breathing, some prana yoga," said Francine Shore of the Educational Alliance, that organises the laughing yoga classes for seniors in Manhattan. "The way I describe it - is it's exhausting - thoroughly exhausting - it really is a workout - it's a real exercise but ultimately exhilarating," she added. Laughing yoga was invented by Dr. Madan Kataria in Mumbai, India in 1995 after observing the health benefits of laughter. Since then it has grown into a worldwide movement with more than 2500 clubs in countries as varied as Vietnam, Finland and Dubai. The seniors in New York City, several of them holocaust survivors, are part of a co-op in lower Manhattan called NORC (Naturally Occurring Retirement Community) that along with The Education Alliance organizes the classes. Initially, many of the seniors were hesitant to laugh loudly and proudly but have since come to look forward to the classes. They help them overcome the challenges of growing older, they said. "You have to laugh because you accumulate a lot of problems when you're older," said Harold Krinsky, a senior student who insisted he be identified as eighty-something. "And it's physiologically all right - your whole body laughs like santa claus 'ho, ho, ho, ha ,ha, ha" that's the way you gotta do it." According to Shore, the body doesn't register the difference between a real laugh and a feigned one and the health benefits, of which there are many, are the same. "There are lots of health benefits to laughter yoga," said Shore. "It increases your endorphins - the feel-good hormones, and decreases the stress cortisol levels. You can burn up to 400 calories in an hour - so it lowers your blood pressure, it alleviates arthritis, aches and pains, decreases depression, anxiety, increases productivity and enhances creativity. So there are many health benefits." But it's not all giggles and fun for the students. It's also hard work. "It really invigorates you. It gets the little endorphins in the system jumping and it gives you a good feeling. Your breathing improves. The only fault I find with it - after the fun is over - I'm ready to take a nap," said Sadie Feinman. Aside from laughing, students also pretended they were chickens. Apparently making a 'clucking' sound is also therapeutic. OLD PEOPLE LIFESTYLE LIFESTYLES