The exercise commonly used to strengthen the core muscles is the plank. Planks involve maintaining a position similar to a push-up for extended periods, engaging the abdominal muscles, obliques, and back. In addition to traditional planks, variations like side planks or dynamic planks can target different areas of the core. Strong core muscles are essential for improving posture, stability, and overall athletic performance. They also play a critical role in injury prevention during various physical activities.