It's hard to imagine millions of people performing aerobics simultaneously, but that happens five times a week in Liu Kent-Hung's livestreams.

Known as Will Liu in English, Liu has been a well-known singer and actor since the early 1990s, and his fame has been enhanced by the Douyin livestreams in which he coaches aerobics.

"I'm happy to see so many people that never took exercise before have now started working out with my livestream because that means they have taken a step toward a healthier lifestyle," Liu told China Daily.

He has been a fitness fanatic for more than 30 years, and has published several books, including A Fitness Book by Kent-Hung?in 2004, and Fitness Can Change Your Life in 2014.

The first book became very popular because Liu was a star actor who had helped his celebrity friends share his fitness experience.

"I wanted to let people know that no matter how busy you are, you have time to work out," he said.

"In the book that was published eight years ago, I wanted to tell people that 'fitness can change your life', even though the publisher said the idea was too advanced and might be hard for people to understand.

"Fitness is not only about losing weight and building muscle — it's a lifestyle that makes you healthier, happier, have a great career and benefits your relationships with family and friends."

He said his current popularity is not something he achieved in several months. Instead, it's the result of many years of work.

"From introducing my family and friends to my fitness regime, to becoming an instructor on TV shows and making coaching videos and livestreams, I have been doing this enthusiastically," he said.