do you slap the mat when doing ukemi? in my previous dojo and many videos I see people always slap the mat when doing ukemi. I was also told that it helps dissipating the force. but in my current dojo, we are told not to make many noises including slapping the mat. I guess the reason is that they don't want to disturb the neighborhood and because the slapping make so much noise when falling that it may scare the would-be student.. but doesn't that make the practice incorrect?
The placement of the hand on the mat before the body touches the mat in a throw lets you know the orientation of your body in reference to the floor. This lets the body decide how to land on the floor.
It does no good to slap the mat after the body hits the floor.
I have taken falls on mats, hardwood floors, asphalt, concrete and the ground in my backyard, whether you slap soft, hard ( without tension in your body) or don't slap at all is like Janet says, it is not a conscious premeditated decision ( except when training to do so ) as it happens too fast.
Slapping to disperse energy may happen but it is not the primary reason to do a slap.