Yoko Gushiken, who made 13 successful defenses of his WBA light flyweight championship before losing his final pro fight, announced Saturday that he is closing down the Shirai Gushiken Sports Gym, where he serves as chairman.

The gym, located in Tokyo, was founded in 1995 by Gushiken and the late Yoshio Shirai, Japan's first pro boxing world champion. It will close on July 31.

"From the standpoint of my physical strength and willpower, I've reached the age where it's hard for me to train athletes with the same passion I have had up until now," he said in a statement on the gym's website. "The time was right for this decision."

Former flyweight world champ Daigo Higa recently abandoned the gym, following his former trainer Joji Nogi out the door.