Translation guide
The exercise where you lie on your back and raise your upper body to a sitting position.
The physical exercise of raising the torso from a lying position.
Literally 'abdominal muscles', this is the most common way to refer to sit-ups as an exercise. Often used in the phrase 腹筋をする (to do sit-ups).
毎日腹筋を30回やっています。
I do 30 sit-ups every day.
Direct loanword from English. Used in fitness contexts, but less common than 腹筋.
シットアップは腹筋に効きます。
Sit-ups work your abs.
Literally 'raising the upper body'. Used in formal or technical contexts, such as physical education tests.
体力テストで上体起こしをしました。
I did sit-ups in the physical fitness test.