Lee Kwang Soo lost his calm on 'Running Man'.

On the September 1st episode of the SBS variety program, the members played a game that required wearing an instrument that tracked the nerve cells of the brain. Whenever the wearer's brain would feel a high or low tension, the instrument would show the gauged level of peace in their mind.

To purposely provoke Lee Kwang Soo, the cast members asked him some sensitive questions, one of them being Yoo Jae Suk who asked, "So, do you get along with Lee Sun Bin these days?"

Since it was known publicly that he and Lee Sun Bin were an item, Lee Kwang Soo suddenly became flustered and didn't answer the question, all while the nerve cells of his brain intensified.

In order to "protect Lee Kwang Soo's composure", no more questions regarding Lee Sun Bin came up. The actor-entertainer then sipped some green tea to calm down his own nerves.