of my clients was talking with me an brought up that before they started working with me one of the things they used to love to do was stand on a BOSU ball and work on their golf swing. If you don't know what a BOSU ball is, see the picture below.
They said we train a lot of balance and coordination but why don't we do anything like that?
I said it's pretty easy, Ground Reaction Forces(GRF).
What are GRFs?
According to Newton's Third Law of Motion,
For Every Action There Is An Equal And Opposite Reaction
We all remember that from school. But what does that mean in relation to GRFs?
When we stand on the ground our body is exerting a downward force on the ground because of our weight and gravity. At the same time the ground is exerting a force back up against us equal to the downward force we are exerting.
As we are all trying to becoming better golfers and want to increase our drive distance, Newton's Third Law is a key concept. When we swing a golf club on a stable surface (like the ground), we drive our feet into the ground to solidify ourselves so that we can create power that will go from our legs to our core to our upper torso to the arms and out through the club.
When we stand on an unstable surface the amount of GRF that is created by us is lower because "For every action there is an equal and opposite reaction". The unstable surface cannot exert enough upward force against our downward force. Meaning that our downward force will be lower to equal the upward force.
So the amount of power you can create and drive up through the body and out to the club goes down.
With all that said there is a time to use unstable surface training, but it generally is used in a rehab setting. Not for creating maximal power.