The lunging hip flexor stretch is great for increasing range of motion in the muscles of the upper thigh. This is a static stretch, which means that the position is held constant. The hip flexors are technically termed "iliopsoas." The function of the hip flexors is to flex the hip (hence the name). The hip flexors are involved in movements that include kicking, stair climbing, and even walking.

To begin, move into a deep lunging position. The knee of the trailing leg should touch the floor. You should feel the stretch in the hip flexors. You can further the stretch by lunging forward more, or by leaning backward. Static stretches are generally held for 10 - 30 seconds. They should never be painful. The general rule is to hold the stretch in a position of mild discomfort.