Strengthens your core !!! – The Plank hold focus on upper and lower body strength, mainly your quads and hamstrings and calves. They help you improve both your upper and lower body strength.
Ultimate Functional fitness!!! - The Plank hold is a core strength training exercise. With every test you will be strengthening your core muscles.
For a full demonstration ask a fitness instructor, Do it! It will give you much deserved challenge!!!