Crunch

Primary target: Rectus Abdominis (腹直肌)

Exercise Details

Equipment: Bodyweight/weight plate
Sets & Reps: 3-4 sets × 15-20 reps · rest 60 s
How to do it: Low back flat on the floor; exhale as the ribs curl toward the pelvis (shoulder blades off the floor is enough); pause 1 second at the top; lower slowly.
Common mistakes: Pulling the neck, sitting the whole torso up (hip-flexor takeover), rushing