Kim Jong Kook, who's nicknamed 'Sparta Kook', has revealed his fear of balance beams!

The July 15th episode of SBS's 'Running Man' consisted of guests Shin Se Kyung, Noh Sa Yeon, and Yoo Joon Sang for a 'Beauty and the Beast' themed 'Princess Race' special.

The 'Running Man' cast members were each split up into three teams and were given numerous missions to fulfill at various locations. For the second required mission, team Kim Jong Kook and Ji Suk Jin had to walk across the floating balance beam which was laid across a pool while giving fellow teammate Song Ji Hyo a piggyback ride.

Confident that he'd be able to easily cross the balance beam, Kim Jong Kook was met with the unexpected as he began to stagger immediately upon setting foot onto the path.

His fellow cast members were stunned by the frightened Kim Jong Kook, an image they've never see before, and remarked, "Is this really Kim Jong Kook?" Even the production team were surprised by Kim Jong Kook's reaction as they left a caption for viewers that read, "Even Sparta Kim Jong Kook, the one who reigned over the 'Running Man' members, kneeled before the balance beam."

Source: Newsen via Nate, TV Daily via Nate