'Are You There God? It's Me, Margaret' Star Got a Bust Exercise 'Master Class' from Judy Blume

"We must! We must! We must increase our busts!"

We imagine that countless Judy Blume fans tried to picture the infamous exercise after reading Are You There God? It's Me, Margaret. But when the film adaptation dropped in April, readers finally got to see how it's done. And according to Abby Ryder Forston, who plays Margaret, the cast couldn't have done it without Blume's help.

While chatting with PureWow, the 15-year-old actress walked us through how she and her fellow cast mates, Elle Graham, Amari Alexis Price and Katherine Kupferer, learned the proper way to do the bust exercise.

In case you need a recap of the scene, Nancy encourages her friends to follow a special "technique" that'll help them get out of wearing smaller bras.

While discussing the scene, Forston told us, "We were rehearsing the scene where we're in Margaret's room, and all of the girls are doing the 'must increase our busts' exercise after they look at the Playboy, and we were rehearsing it. And apparently, Judy was talking to Julie, one of the producers, and was like, 'Oh, no, I have to stop them. They're doing it wrong. I have to show them how to do it.'"