A classic move from gym class, the sit-up works the abs and hip flexors through a wide range of motion. When doing sit-ups, remember not to lace your hands behind your head, which can put too much pressure on your spine and neck. Instead, place your hands behind your ears with palms facing forward, or cross your arms over your chest, and make sure your feet are planted firmly on the floor. Here's how to do a sit-up.
Now that you've mastered the basic sit-up, here are three more sit-up variations to challenge yourself.