Yes he is a kyokushin Karate Kaz and a Sensei he is a big Hollywood Star with Great Physique.
You Can See his Photos in Kyokushin Dogi and Training.

http://www.shinkyokushinspain.com/06_album/htmls/person/dolph.htm

You can Also See his Photo with Sosai

http://www.superkarate.ru/k_s_lundgren.htm