Gymnastics
Noun, する verb, and の adjective
たいそう
この体操は見た目よりもずっときついんですよ。
This exercise is actually a lot harder than it looks.
Take your body and manipulate it around for exercise. This is Calisthenics or gymnastics.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.