Leaning forward places a runner's center of mass on the front part of the foot, which avoids landing on the heel and facilitates the use of the spring mechanism of the foot. It also makes it easier for the runner to avoid landing the foot in front of the center of mass and the resultant braking effect. While upright posture is essential, a runner should maintain a relaxed frame and use his/her core to keep posture upright and stable. This helps prevent injury as long as the body is neither rigid, nor tense. When leaning forward, focus on leaning only slightly from the waist and the rest of the body will naturally follow. The most common running mistakes are tilting the chin up and scrunching shoulders.