Yoo Jae Suk showed off unexpectedly fit arm muscles.

Recently on an online community, a picture was posted under the caption, "Yoo Jae Suk filming for 'Infinite Challenge'".

In the picture, Yoo Jae Suk can be seen filming for MBC "Infinite Challenge" with HaHa on a street. He is wearing a casual gray shirt and is smiling at something. But what caught the attention of internet users was his arm muscle.

Yoo Jae Suk's arm muscle has already become an issue a few times in the past. His arm shows that he has been keeping up with his work outs, and it is not any inferior to arms of idols in their 20s.

Internet users who saw this commented, "Our righteous national MC", "What are you laughing at", and "He must have worked out really hard."

Photo Credit: Online Community