Bowing is an act reserved for Allah Ta’ala. Martial arts is not confined to simply physical training. It has a spiritual dimension to it, such as meditation and obedience to the teacher. It can be likened in one way to a religion.
Thus, there is all the more reason that one should abstain from this type of bowing, which at times even resembles Sajdah. Try and find a Muslim instructor and explain to him that bowing in this manner is against the teachings of Islam, hence, you will not bow.
and Allah Ta’ala Knows Best
Moulana Imraan Vawda