Millie's personal trainer Rich Tidmarsh took a snap of the former Made in Chelsea star in a deep wall squat, giving her toned thighs a serious workout...
If you want to have a go at Millie's feel-the-burn workout, all you need is a wall and buns of steel.
HOW TO DO A WALL SQUAT
1. Stand a foots width away from the wall, with your feet placed as wide as your shoulders.
2. Stretch your arms out above your head and place your hands on the wall.
3. Send your hips back and lower yourself down under control into a deep, full squat. Don't let your hands leave the wall, and don't let any other part of your body touch the wall.
4. Think about pushing your knees out and your chest up. This should help you get a good position, and will keep your torso tight.
5. Feel the burn.
6. Push slowly back up, concentrating on using your thigh and bum muscles. The slower you push, the harder the muscles work. Repeat.
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