A sit-up is a common exercise that primarily targets the abdominal muscles. To perform a sit-up, an individual lies on their back with their knees bent and feet flat on the ground. They then lift their upper body towards their knees while keeping their hands behind their head or crossed over their chest. This movement helps strengthen the core and improve overall stability. Sit-ups can be part of a broader fitness routine that includes other exercises like crunches, planks, and leg raises. While effective for building core strength, it's important to perform sit-ups with proper form to avoid strain on the back and neck.