Sheikh Faysal Mawlawi, deputy chairman of the European Council for Fatwa and Research, states: “A Muslim should shun all games and sports that contain rituals and practices which contravene the teachings of Islam, irrespective of their names or titles. If sports and games are free of such non-Islamic practices, a Muslim is permitted to involve in them.
It is a custom in some martial arts that players greet each other by bowing. Then, if this practice is meant to be an act of worship, it is impermissible for a Muslim to involve in.
However, if it is meant to be a form of showing mutual respect between players, and not in form of ruku` (bowing) in salah, then it is permitted from the Islamic point of view.”