Using the ground means applying force into the ground to make your body move where you want. Athletes use the ground in every sport whether they think about it or not. In fact, some of the best athletes in the world have probably never thought about using the ground because it happens naturally to them.
Imagine a defender in basketball pivoting to the left to stay in front of the player he is defending. In order to move left, he must apply force into the ground to the right. The amount of force he applies to the right determines how fast he can move to the left. This illustrates two simple points; the degree which you apply force into the ground largely determines how fast you can move, and the body will always move in the opposite direction where force is applied.
Have you never watched Rory Mcilroy swing in slo motion? He creates a significant amount of knee flex early in the downswing, As he moves closer to impact, he’s loses the knee flex as he pushes into the ground. This allows his body to to accelerate even faster to create maximum club head speed. This is part of what makes downswing so dynamic and powerful.
How can you learn to use the body like this? Check out my online program called Fit For Speed. It includes lessons from me on how to use the body efficiently and effectively to maximize swing speed. It also includes a 6-week speed training program and fitness exercises to improve your strength and mobility.