YOU SAID:
Expand your chest, and avoid rounding your back!
INTO JAPANESE
胸を広げて、背中を丸めないようにしましょう!
BACK INTO ENGLISH
Spread your chest wide and don't curl up on your back!
INTO JAPANESE
胸を大きく広げて、背中に丸まらないでください!
BACK INTO ENGLISH
Spread your chest wide and don't curl up on your back!
That didn't even make that much sense in English.