A plank workout is pretty straightforward (literally!). The basic plank starts face down, in push-up position, with only elbows and toes touching the ground and making sure your shoulders are in line with your elbows. The object is to hold your body taut, with spine straight as a plank, sucking in your stomach muscles, and using mostly core strength to maintain the position. Hold it for as long as possible until you start to shake…and then relax. Few exercises are as effective at working multiple body parts all at once, and doing plank exercises will turn midsection bulk into toned shapely muscle. As we keep the hustle on to shed layers and show more skin during the warmer months, here are some variations on this powerhouse pose to whittle your waistline and strengthen your core. Trust us—you’ll plank us later.