On the October 13 episode of "Running Man" with guest star Kim Min Jung, fans noticed Kim Jong Kook's back covered in medical tapes and expressed their concern for the singer.

Representing his team (Gary and Kim Min Jung), Kim Jong Kook stepped forward and took on Chun Jung Myung in the battle of strength. During this segment, the singer's shirt rode high enough for fans to see his back, bringing in worried comments from the viewers.

Some of the comments say, "It's amazing how hard Kim Jong Kook works," "I've never seen Kim Jong Kook show any sign of pain or struggle," and "It seems like the medical tape is helping."

In August 2010, Kim Jong Kook underwent lumbar microdiscectomy back disk surgery, and has since then used medical tape to aid in easing the pain and protecting his back.

Meanwhile, he revealed his weight to his cast members after overwhelming the opponents with his strength and ripping Yoo Jae Suk's shirt during the game. The host-comedian comically exploded in anger and said, "You're not in the same weight level as us. Is it okay to rip's shirts of other people? How much do you weigh anyway?"

To which Kim Jong Kook replied, "I weight 78kg (172lbs). Honestly."