The movie is about a medical engineer (Bullock) and an astronaut (Clooney) who are stranded in space after debris from a satellite crashes into their space shuttle.
Asked about how they trained for the role, Clooney said, "Sandy and I did a lot of Bikram yoga together."
"We're good that way. Very flexible," Bullock added.
Bullock, who called her role in the film the "most challenging" she's had thus far, told reporters she also trained with real astronauts.
"They were incredibly helpful, and they gave me an inside visual as to why they do what they do,” she said. “It was the craziest, most bizarre, and most challenging shoot I’ve ever done.”
Regarding how she stays in such good shape at 49, the "Heat" star explained she thoroughly enjoys dancing.
"I love to dance, I have a background, I was a gymnast, I was a dancer, I just don't like gyms I'm very bored so I'm just cardio, music, just blast the music for an hour and don't stop moving your body. Lightweights," she said. "I have a 40 pound 3-year-old who still is a baby and insists on being carried so I must stay strong. So just that."
Clooney, who in a separate interview credited "doing yoga and drinking" as his preparation technique for the role, said he chose to star in the film because of the script.
"In general, through my career and certainly in the last 15 years of my career, I just try to find really good scripts and if there's something that I can do in them," he said.
The 52-year-old actor added that “moving slowly to mimic the way the body moves in space while speaking normally,” was his biggest challenge while shooting.
"Gravity" hits theaters October 4th.