Reverse crunches are a core-strengthening exercise that primarily targets the abdominal muscles. To perform a reverse crunch, lie on your back with your arms at your sides and your knees bent at a 90-degree angle. Engage your core and lift your hips off the ground, bringing your knees toward your chest. Hold for a moment before lowering your hips back to the starting position. This exercise can help improve core stability and strength, making it beneficial for overall fitness. It is often included in abdominal workout routines and can be modified for different fitness levels by adjusting the range of motion or adding weights.