Players apply resin to the bottom of their shoes to get more grip
on the foot.
Resin increases the friction on a smooth floor or on the badminton court.
It is somewhat
desert => sand + high temperature. High temperature may increase friction,
but if the surface melts a little under the pressure of the foot and high temperature,
then the coefficient of friction may decrease.
When a man or a heavy animal step on a smooth surface, they will tend to lose
balance. If they are stepping front foot on the smooth surface with the back foot
on loose sand, it is difficult to stay put vertically. The loose sand may not be able
to give sufficient friction on the back foot & push him ahead. Front foot has not
fully gained its vertical position yet and it does not get enough friction to pull the
person forward. Person or animal is likely to fall and hurt the legs.