United Kingdom, Sept. 7 -- Donna Mills still does 100 sit-ups a day at the age of 85.

The Knots Landing actress has no plans to slow down and sticks to a tough exercise regime every day, as well as enjoying regular sessions on the tennis court.

She told Fox News Digital: "I do 100 sit-ups a day, 50 leg lifts, lots of stretching. I have a ballet barre in my little gym.

"And ride the bike for about 45 minutes or an hour.

"I play tennis five times a week sometimes. And so that's very, very important."

Donna also still sticks to a strict diet and never indulges in sweet treats.

She said: "I've always been anti-sugar. I read a book a long time ago called 'Sugar Blues' that really talked about the sugar industry and everything, and I have...