Grandmother, 63, and granddaughter, 18, shoot to Insta stardom

A grandmother and granddaughter have shocked Instagram with their shredded physiques and fitness videos, proving age really is just a number.

When fitness freak runs in the family, you end up with Tia Christofi, 18, and her grandma.

The pair recently posted a video in which they hit the gym together — matchy-matchy activewear included, of course — and social media users went wild.

Tia’s grandma, Lesley Maxwell, 63, matches her granddaughter rep for rep, proving that age is just a number.

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Tia’s 113k followers went wild for the pair’s joint video, garnering comments like “The coolest grandma I’ve ever seen” and “Is grandma single?”

In the video, the two are seen completing a series of weightlifting and circuit training exercises without breaking a sweat.

After posting the footage on her Instagram, Lesley’s 21k followers also thought the Melbourne duo were “sexy” and “inspirational”.

Both grandma and granddaughter aren’t shy when it comes to Instagram and showing off their gains.

While Tia’s still in high school — and has already collaborated on her own activewear line — Lesley is a former figure sculpting world champion. These days, she helps the rest of us ‘Bring Your Sexy Back’ with her 90-day program.

Did someone say booty day? Picture: Instagram / tiachristofi

Lesley shows Tia how it’s done. Picture: Picture: Instagram / tiachristofi

The former fitness competitor has over 30 fitness titles under her belt and says fitness has been a lifelong passion of hers.

“I had always had a keen interest in fitness and health and I was determined to find a way to nourish my body to look and feel younger,” she told Metro.

“I used to love being strong and winning bets with boys that I could lift more than them.

“My mum used to tell me ‘boys don’t like girls with muscles’ — but I know they did.”

Her advice for those wishing to get her enviable physique?

“Train with weights to create a younger-looking body, as it can really lift and tone bums and arms better.”

Lesley after winning the World Figure Shaping Championships in the USA. Picture: Supplied

Her granddaughter Tia has clearly taken that advice on-board. The teen regularly shares her workouts on Instagram using everything from weight plates and booty bands to boxing in order to keep challenging her body.

And it’s paid off. Not only is she incredibly fit, the 18-year-old has already built up a staggering following that already earns her $75k a year in promos and endorsements.

“I’m selective with who and what I represent as I want my followers to know that I promote products that I actually like and believe in,” Tia told Daily Star.

Giving advice to others, Tia revealed: “Post what you’re passionate about and don’t care what anyone thinks of you. Be true to yourself.”