Posture is the way your body is positioned when you're standing, sitting, or lying down. Correct posture puts the least amount of strain on your muscles and joints. Slouching, slumping, and other types of poor posture can cause muscle tension, as well as back pain, neck pain, joint pain, and reduced circulation. Maintaining proper posture isn't the only important factor in reducing pain, it's also important to make sure you're not in the same position for too long.