The plank is considered a very effective isometric abdominal exercise. It's generally believed capable of strengthening all the muscles of the abdomen, even the underlying muscles that help stabilize the spine. Fitness experts often recommend the plank exercise to those wishing to building core strength, because it can also act on the muscles of the hips and back to strengthen the body's entire core. The exercise is generally performed by assuming a sort of push-up position, balancing on the elbows and the tips of the toes. The position is then held for 15 to 30 seconds per repetition.
Good form is generally necessary to make this exercise provide its maximum benefits. In order to perform the plank exercise most effectively, fitness experts recommend using the abdominal muscles to hold the spine steady, rather than allowing it to sink toward the floor. Most people perform this exercise with the elbows on the floor, directly beneath the shoulders, and the forearms flat on the floor.
Balancing on the tips of the toes, as if about to perform a push-up, is generally considered the most effective form of this exercise. For those who are just beginning to build core strength, the knees can be dropped to the floor, to modify the plank somewhat. A modified plank can help exercisers build the necessary core strength to progress to the full plank.
The plank, or modified plank, should generally be maintained for at least ten seconds. Those who have developed a higher level of core strength may be able to hold this position for as long as 30 seconds per repetition. The body should generally be held in a steady line, to activate the muscles of the abdomen, hips and back.
Most fitness experts advise sucking the belly button in towards the back of the body to keep the back from sinking towards the floor. Elevating the hips slightly above the level of the rest of the body can help those who struggle with this exercise. Trembling in this position is often considered a normal sign that the muscles of the core are activated and gaining strength.
This exercise can be difficult for those who don't have a lot of core strength, especially since it usually works the transverse abdominus, which may be one of the innermost abdominal muscles, responsible for stabilizing the spine and the body's core. Most experts believe that this muscle is more important to core strength than the rectus abdominus and the obliques, which, when toned, can give the abdomen a "six pack" appearance. While the plank may be a challenging abdominal exercise for many, most fitness experts believe that it can help strengthen the deep muscles of the body's core very quickly.