Doing the plank is not a complicated exercise, but getting it exactly right is important if you want to build up your core strength. For a forearm plank, often considered the most common form to do a plank, lie on your stomach, rest your forearms on the floor, put your feet up, lift your pelvis, then hold. The plank is one of the best-known fitness exercises, and rightly so, as it trains the core muscles particularly effectively, says Sven Seidenstücker, a lecturer at the German University for Prevention and Health Management. Your core is the ring-shaped corset of muscles around the centre of…