I know half of them are "delinquents" and probably skip PE, but "big boobs shake when you run" shouldn't come as a surprise to them. I can understand awakening to Saotome's male gaze for the first time, but everything I've heard indicates that having the twins flop around is uncomfortable at best regardless of who's watching. So if they've ever run in the past three years, they would know how much it sucks! And of all the girls running, the cheer girls should understand the power of doubling or tripling down on sports bras!