Gina Stewart, 49, dubbed the “World’s Hottest Gran”, isn’t shy when it comes to showing off her youthful physique.

 Kiwi grandmother has amassed a cult following over her racy bikini snaps which she regularly posts to Instagram and now she’s revealed the three minute “secret” behind her ageless looks.

mother-of-four and grandmother-of-one revealed that she endures temperatures of -110C to “rejuvenate” her body.

hyper-cooling remedy is known as cryotherapy and is used for muscle fatigue, muscle repair, injury treatment plus general skin revival.