World's 'most youthful' mother, 50, flaunts her super toned body while doing yoga at MINUS 40F (and she reveals exercising in winter is her secret to staying young) (15 Pics)

Liu Yelin, from China, has worked out in winter outdoors for over 30 years

The mother-of-one stressed winter swimming helps her get flawless skin

Often appearing in bikini, energetic Ms Liu said she felt she was still 15

The 50-year-old ex-librarian has been dubbed the world's 'most youthful' mother

Not a couple: Ms Liu (pictured with her son) said she is often mistaken for her son's girlfriend