Answered by Shaykh Ali Laraki al-Husaini
Question:
If one wants to train in an Asian Martial Art is it then permissible to bow, like it is done in Karate for instance?
Answer:
Assalamu alaikum
This is a matter that has concern me as a karate student and teacher[1]. What is haram is to do ruku’. The Japanese bowing is not ruku’ because the angle of bowing is less pronounced than the one needed for ruku’. I have also found in a commentary of the Risala (al-Fawakih ad-Dawani by an-Nafrawi) that some ulama are of the opinion that bowing (inhina’) is allowed if it does not reach the level of ruku’.
And Allah knows best.
Shaykh Ali
Footnote:
[1] Besides being an Islamic (Maliki) scholar Shaykh ‘Ali Laraki al-Husaini (hafidhahullāh) is also a Sensei, a black belt in Shotokan Karate and Judo.
This Q&A is also available in Danish here
source : http://www.muwatta.com/bowing-in-martial-arts/