What muscles do trunk curls work?

Trunk curls primarily target the rectus abdominis muscle, which is the long, vertical muscle that runs down the front of the abdomen. While this is the main muscle worked, trunk curls also engage:

External obliques:

Located on the sides of the abdomen just outside the rectus abdominis.

Transverse abdominis:

The deepest abdominal muscle that wraps around the waist like a corset.

Internal obliques:

The muscles located beneath the external obliques that run diagonally upwards across the sides of the abdomen.