Every morning, crowds of elderly people can be seen working out in China's public parks.

Temple of Heaven Park is one of the hot spots for the elderly in Beijing. Every corner of the park seems to host some novel exercise - from walking backward to kicking shuttlecock, square dancing, and Tai Chi.

But the most eye-catching groups in the park are the so-called "Kung Fu Grandpas/Grannies," whose workout videos have gone viral on social media platforms like Youtube and Douyin. On the exercising bars, these 60s and 70s display eye-opening flexibility and strength. Most of them were ordinary workers from different industries that only started working out after their retirement. They say age is just a number when it comes to fitness.

Social connection is also what the elderly seek during their morning workout. Seventy-two-year-old Feng plays diabolo, also known as Chinese yoyo, every day. He has kept this exercising routine for six years and now he's managing a Wechat group of 27 members who share the same hobby.

"What I like about this place is that newcomers are always welcome," said Feng. "I didn't know any diabolo tricks before, but those seniors taught me and practiced with me. Now, I'm able to teach others. It's like a team."