Sit-ups are a classic core exercise that primarily targets the abdominal muscles. They help strengthen the core, improve stability, and enhance overall fitness. By lifting your upper body towards your knees, you engage the rectus abdominis, obliques, and hip flexors.

1. Lie on your back with your knees bent and feet flat on the ground.
2. Place your hands behind your head or cross them over your chest.
3. Engage your core and lift your upper body towards your knees.
4. Slowly lower your upper body back to the starting position.