Having strong abdominal muscles and a strengthened core is both aesthetically and physically beneficial. Since the abdominal muscles are involved in most twisting and bending motions, strengthening your abs can prevent damage to your spine as you move and lift heavy items. Though most people want strong abs, many people end up doing inefficient exercises that do not actually activate all of the abdominal muscles at once. The plank is a more beneficial exercise because it actually works out all of the abdominal muscles together.
The plank exercise is important because it actually works out all six of your abdominal muscles. The rectus abdominis is the band of muscle stretching along your belly that can look like a six-pack, and this is typically the only muscle that people focus on while working out. However, the abdominal muscle that does most of the back-supporting work is the transverse abdominus, which is a deep band of muscles that wrap around the torso. There are also four sets of oblique abdominal muscles because there is both an internal and an external oblique muscle on each side. Most people just do endless crunches when they want to work out their abs, but these are ineffective because they are not working out the transverse abdominis or the internal obliques.
The plank exercise is a little unusual because it is an isometric exercise, where you work out your muscles without performing repetitive movements. Isometric exercises are often beneficial because they strengthen many muscles at the same time. To properly perform a plank, start out in pushup position. Bend first one elbow and then the other to a 90 degrees angle with your weight rested on your forearms, so only your toes and your forearms are touching the floor. Do not let your torso sag towards the ground, and do not let your buttocks rise above your head. Instead, your body should form a straight line going from your head to your feet. Your head should be looking down at the floor, and your elbows should be beneath your shoulders. Hold this position for as long as possible.
At first, many people can only hold this position for about 15 seconds or so. However, if you keep doing a plank and holding it for as long as possible each day, you will gradually be able to stay in a planked position for a longer amount of time. Your goal should be to eventually be able to stay in a plank position for two minutes. Most people find that by steadily doing a plank each day, they can gradually increase their planking endurance to two minutes within 30 days. By the time a person can plank for two minutes, they will notice a significant difference in abdominal strength, and their core will appear more toned. You can just keep doing longer and longer planks each day to strengthen your abs, or you can start increasing the difficulty by raising either one leg or one arm off of the ground.