  In this paper we face the problem of safety connected to a class of throws
that are more often applied in every level of competitions. However, to our
knowledge it has never been a scientific study on this subject in Japan and, to
our great amazement, in Europe, only one, and in very recent times. While the
family of techniques that is applied with two knees on the ground has gone over
time, increasing, without increasing the immediate traumas. this posed the
problem if these techniques were really dangerous. It was decided to
investigate in a comprehensive way, on the immediate traumas, by Biomechanics
of the technique aimed at the safety of Tori, from children in the dojo up to
high-level competitions. With the purpose to clarify: if the technique is
dangerous, in its correct execution, for children and athletes, if the
technique is dangerous for the accumulation of traumas in the long run build up
a mathematical model of interaction between knees and Tatami. The experimental
part was developed with a thermal imaging camera that allowed to highlight the
actual impact surfaces and therefore to trace the stress received by the knees,
both for the children and for the athletes of the Italian National Team. the
results have made clear that, if well done and on a certified tatami, the
technique has a negligible probability of immediate trauma.
