Answer
Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
If bowing is meant to be an act of worship, it is impermissible for a Muslim to involve in. if bowing is meant to be a form of showing mutual respect between players, then it is permitted.
As far as sports and games are concerned, Sheikh Faysal Mawlawi, the late 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 bowing is meant to be an act of worship, it is impermissible for a Muslim to involve in.
However, if bowing 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.
For more about sports, see these fatwas:
What Does Islam Say on Risky Sports?
Is It Haram to Wear Shorts for Sports?
Allah almighty knows best.