Thousands of people are preparing to gather at events around the world to mark the first International Day of Yoga, as India pushes to raise awareness about the ancient discipline.

Events will be held on Sunday in 177 countries, including Australia, where yoga practitioners will gather in cities and towns across the country.

The idea of a yoga day was first mooted by Indian prime minister Narendra Modi, a yoga practitioner himself, who spoke about the benefits at the UN general assembly in November last year.

Yoga lets people "discover the sense of oneness with yourself, the world and the nature", Mr Modi said at the time.

More than 35,000 people will gather in New Delhi for a half an hour public yoga session which will begin at 7:00am (local time), hoping to secure a place in the Guinness Book of World Records.

Ancient practice being absorbed into everyday Australian life

Yoga, an age-old practice, has grown exponentially in recent times and is enjoying unprecedented popularity in the West.

Bhanu Bhatnagar, who has been practicing yoga for over 8 years, does the headstand pose. ( Supplied: Richard Pilnick )

Bhanu Bhatnagar, a filmmaker who recently directed a film about yoga, said he noticed a change even after his very first class.

"When I walked out, I felt just physically different. I felt calmer. I felt like I had better posture. I just felt more at ease with my body," he said.

Yoga Australia CEO Shyamala Benakovic said yoga was becoming more mainstream in Australia.

"There's been a lot of research and studies showing the benefits of yoga — it's across all age groups, from children to senior ages," she said.

"The major trend is that it is being absorbed into everyday life. So you will see more and more corporations having [yoga programs].

"It is becoming part of sports — they do a lot of yoga. It's becoming part of the school system."

Ms Benakovic said yoga's malleability allowed people to work it into their life in any way they want.

This has resulted in many variations of yoga, from hot yoga and board yoga to more extreme forms such as nude yoga.

Yoga practitioners still flexible in their 80s

Yoga teacher and former hotelier Bette Calman, 89, attributes her good health to the discipline.

"I have never had a headache or a cold," she said.

Ms Calman said yoga helped her manage the muscle aches she experienced while working in the hotel industry, a result of standing on her feet for hours at a time.

"I would get behind the bedroom door and stand upside down. I knew it took all the pain away from those tired legs," she said, referring to the headstand pose.

"It is sensible relaxation and it is sensible exercise and it just makes you feel recharged and revitalised."

She said she "fell in love" with yoga about 60 years ago and has never stopped practicing since, adding that the shoulder and headstand poses are among her favourites.

"I think the shoulder stand gives me the energy that I demanded out of life," she said.

"I have been the one that had little sleep and always had plenty of energy."

Bette Calman, who has six decades of experience in yoga under her belt, does the dhanurasana, or the bow pose believed to massage one's abdominal organs. ( Facebook: Bette Calman )

Controversy ahead of yoga day

But in the lead up to yoga day, tensions have flared among religious communities in India.

Some Muslim activist groups say Muslim yoga practitioners do not want to chant "Om", which has Hindu origins, but rather chant "Allah".

Others expressed concerns over performing the Surya Namaskara, also known as the sun salutation, which they say violates the monotheistic nature of Islam.

Nevertheless, India is experiencing a renewal of interest in yoga, especially among its younger generation.

Anil Kumar Ganeriwala, from the Ministry of Ayurveda, Yoga, Unani, Siddha and Homoeopathy (AYUSH) said there was a growing interest in yoga among Indians.

"In the last two decades it has reached every home. It is no more confined to Himalayas or saints and sages," he said.

People gather at Sydney Harbour for a yoga session. ( Twitter: @MEAIndia )

Despite its controversy, yoga is one of India's most successful cultural exports.

However, Mr Bhatnagar, who became a yoga teacher four years ago, said the practice could not be bought.

"Yoga can never really be owned. Yoga is experienced — it's not performed or done or practiced. No-one can ever own your experiences," he said.

"I don't think it's ever possible to own yoga, just like it's impossible to own tai chi or karate."

About 20 million people are estimated to regularly perform the exercises in the United States and they spend an annual $US10 billion on classes and related products, a 2012 study by yogajournal.com found.