"This is beginning to bring back bad memories," groans actress Lashana Lynch, as she does her umpteenth shuttle run to a soundtrack of the former Olympian Shani Anderson barking: "Get those knees up!"
Lynch stars in Fast Girls, a British film out next month which portrays the fortunes of four women on a fictional British sprint relay team. Lynch and her co-star Dominique Tipper are at the Crystal Palace National Sports Centre in London, reliving the gruelling training they went through for the film last year.
Anderson – who ran the relay and 100m for Britain in the Sydney Olympics – was their personal trainer in the months before filming started last winter. "We'd be training for three hours and then I'd be like, right, time for some abs work," she said. "I used to make them do planks. I was popular, as you can imagine." Also on hand to check on their athletic prowess this time is Olympic gold medallist Christine Ohuruogu. "I'm impressed!" Ohuruogu says, as the women detail their brutal regimen of ice baths, repeated stair sprints, abdominal work and weight running that got them looking and moving like athletes.
Ohuruogu is pleased that they were made to take it seriously. "It's good, because people think we just turn up for the Olympics and eat cake the rest of the time."
In case further proof were needed that being an Olympian takes more than eating cake, Anderson and Ohuruogu suggest I have a go at running alongside Tipper and Lynch. The first drill is strides, which Anderson assures me are "easy", suggesting: "You just run a bit faster than a jog." I take a few steps at what seems an appropriate speed, only to see Tipper and Lynch already at the finish line. "You sure that wasn't a sprint?" I grumble, puffing my way across the line. "Er, no," Tipper says, trying not to laugh, "definitely not."
Tipper, who made her film debut in Adulthood, says she, Lynch and their co-stars Lenora Crichlow and Lily James stuck to an extreme lifestyle to make sure they looked realistic. "Our lives turned into those of athletes – we had no social life and all I thought about was what meals we could have and when we could sleep. We had to change to a high-protein diet and we were running and then going off to do weights and sit-ups. It was hardcore: there was no taking it easy."