The plank is one of the best exercises you can do for your core because it builds isometric strength to help sculpt your waistline and improve your posture, balance and flexibility. And it is also engages other major muscle groups like your back, arms, shoulders, glutes, and hamstrings.
This is a static exercise which involves maintaining a position similar to a push-up for the maximum possible time.
Even though you aren't moving or lifting weight, you have to constantly squeeze your abs to hold the position.
This exercise is great for beginners since it is easy to learn requires no equipment and can be performed just about anywhere.
Don't feel bad if you can't hold on for long time at first. most people can't last 30 seconds in their first try. keep practicing, and you'll improve in no time.
Do not collapse the lower back. Instead of compromising the lower back by dipping the bum, engage the core by imagining your belly button pulling in toward the spine. This will help keep the torso flat, and in turn, the spine safe.
Don't raise your butt too high. To make the best out of this exercise your body should form a straight line. Although it will feel easier to raise your butt up, keep your back flat enough so your abs feel engaged from top to bottom.
keep your head in a natural position. do not let your head drop down, think of it as an extension of your back. Keep your eyes on the floor, letting them rest about a foot in front of the hands.
Remember that is more important to keep a good form then holding for longer time. When your form begins to suffer, it’s time to call it quits. If the back begins to bow or the shoulders start to sink in, take a break.