In other words, in the process of running, there is little difference between the vertical sub speed of elite athletes and the general population, while the horizontal sub speed is significantly higher than that of the general population
.
In addition to the forward movement, there are up and down fluctuations and left and right swings
.
The fluctuation difference of the center of gravity of excellent marathon runners is generally 7-9 cm, and that of ordinary runners is generally in the range of 8-10 cm
. 
It may be more appropriate to call it “center of gravity fluctuation difference”, which is also a concept in the practical course of road running
.
Therefore, we should master the correct technology of running, strive to move the body center of gravity smoothly, reduce left and right shaking, and reduce the fluctuation difference of the body center of gravity up and down
. 
The difference between up and down fluctuations is called the center of gravity fluctuation difference
.
The unreasonable running technology (such as excessive back pedal angle) is the main reason for the large body center of gravity fluctuation difference
.
Many runners on the Internet refer to the fluctuation difference of the body’s center of gravity during running as “vertical amplitude”, which I don’t think is very appropriate
.
The external force acting on the athlete’s body makes the body’s center of gravity unable to move in a uniform straight line
.
In order to explain the problem more clearly, we introduce the concept of “center of gravity fluctuation ratio”
.
The fluctuation ratio of center of gravity can better reflect the advantages and disadvantages of en route running technology..
.
If an excellent marathon runner’s center of gravity fluctuation difference = 9 cm and step length = 170 cm, his center of gravity fluctuation ratio is 9 / 170, about 5.3%; If an ordinary marathon enthusiast’s center of gravity fluctuation difference is 10cm and the step length is 100cm, his center of gravity fluctuation ratio = 10 / 100, about twice that of an excellent runner
.
The size of the body center of gravity fluctuation difference is related to the running technology
In fact, we ignore the step size factor
.
The step size of excellent athletes is much larger than that of the general population
.
It seems that the difference between ordinary athletes and excellent athletes is not large, and there seems to be little technical gap
.
Namely: Center of gravity fluctuation ratio = center of gravity fluctuation difference / step length
.
Vertical amplitude is a physical concept, which is not suitable for describing the law of human kinematics
.