It's very important to support the foot directly below the body. Many runners are accustomed to landing with the foot in front of the body, which makes it difficult to pull the foot up again with the strength of their thighs. The book calls the moment when the supporting foot touches the ground "the key posture" to show that the action at this moment is the core of the whole "posture running method". At this time, the shoulder, hip and foot landing position is basically a vertical line. It is suggested that the reader can practice the static posture in front of the mirror in order to solidify this key movement. When the supporting foot is pulled up, the body relaxes and the other foot will land naturally by gravity. Of course, you should also pay attention to the position of the landing is still below the body, so that you can feel your legs moving smoothly like wheels. If you try to run a few steps with the action mentioned above, you will find that in order to achieve each landing under your body, your stride will certainly not be very large, and your thighs will not stretch too much when you pull your feet off the ground. Otherwise, you will always be in the "catch-up" state of your feet and return to the forepaw position. As with the debate on landing posture, the contradiction between stride length and stride frequency is also a problem for runners who want to improve their performance. In this book, the author stands very clearly on the side of small stride and high stride frequency, not only because the action essentials of "posture running" are consistent with this, but also pointed out that when large stride landed, the leg was basically in a straight line, and the knee was impacted more heavily, which would increase the risk of injury. In contrast, when landing at a small pace, there is a certain angle between the thigh and the leg, and the muscles will share the pressure on part of the knee, thus playing a protective role. Can you still run fast in this way? The author cites many successful runners, and even some sprinters who require higher speed, such as Michael Johnson, whose secret of success lies in higher stride frequency, which ensures that you can still run fast with small strides. In the previous section, we mentioned that the shorter time of touching the ground when landing improves the efficiency of running. Natural and smooth continuous movements provide guarantee for the high stride frequency of "posture running". For upper limb movements, the author also made a clear explanation. In the book, the author emphasizes that the body should lean forward slightly, noting that this is a whole feeling, if there is a bend, just the upper body forward is the wrong action. The author explains that this forward tilt ensures that the body can make better use of gravity in running in accordance with the landing motion of the supporting foot, thus making the whole running posture more coordinated. Readers can easily grasp the essentials of this action in downhill running. Simply put, the forward leaning of the body is also to create a feeling similar to downhill running. The whole body is pulled by gravity to improve the efficiency of running. In addition to this, other parts, such as the arms, need only natural droop, do not need to deliberately swing the arm to drive the body, upper limb muscles should also be in a relaxed state. In the process of running, there is no need to step down, or use consciousness to control the foot landing position, which will make the running posture become rigid and affect the fluency of the overall movement.