He worked hard to strengthen his abdominal muscles.
waistline
Frequency:
60
%
She measured her waistline to track her progress.
midriff
Frequency:
50
%
She wore a crop top to show off her toned midriff.
Idiomatic Expressions for midsection
Phrase: tighten the midsection
Meaning: to tone or firm up the muscles in the abdominal area
Usage: She started doing sit-ups to tighten her midsection.