Question: Is it permissible to bow before a karate instructor?

Answer: Islam totally prohibits bowing and prostrating before anyone besides Allah Taʿālā. In fact so severe is the warning, that the ʿUlamā are unanimous that if a person bows or prostrates before anything besides Allah Taʿālā, there is fear of him losing his Imān.). Therefore the instructor should be informed that this is contrary to the religion of Islam and that it should be stopped immediately and instead, Salām should be made. If this is not possible, then another instructor should be sought or otherwise this form of self defense should be stopped and some other exercises adopted which are free of such practices contrary to Islam.

(Fatāwā Hindiyya vol.5 pg 369)

And Almighty Allah Knows Best.