breaking news from the olympic games. the greatest gymnast of all times, simone biles, has pulled out of a second competition. >> i'm not sure this kind of conversation about athletes has ever been normal before. >> as quiet as it's kept, gymnastics is as hard and pressure-filled a sport as they come. football is tough, but they wear pads. the only pads you see here -- >> whoa! >> are the callouses. >> oh, my hamstrings! >> all right. cartwheel. >> oh, this is -- you better get way in front of me. >> got it! >> so i don't know if you guys know this, but competitive gymnastics is really hard. >> just a little bit. >> just a tad. >> coaches sarah, breanna mcneil have been teaching gymnastics