According to sharia, one may engage in sports activities to enhance good health or preparation for jihad.
However, this sport does not bring any benefit to the person and it can cause much harm and many health problems to those who perform it. It can even cause death. Also being negligent and careless from performing any obligations like prayer or exposing private parts of one's body are forbidden as well, so it is unlawful to take it as a profession.
As for training purposes it will only be permissible with the following conditions:
a) His attire confirms to sharia regulations
b) His involvement in such a sport does not make him negligent of his religious obligation i.e prayer etc.
c) No form of gambling should be involved.
d) Intermingling of sexes does not take place.
e) His intention be solely to build the physique in preparation for Jihad.
One must keep in mind that you don't injure your partner.