When Lee Byung Hun read the script for "Red 2," he saw that the assassin he played was described as having a "perfect body." And there would be a nude scene. So the "Iris" star worked out as much as he could. Creating the perfect abs takes him about three months, he said. And fans would say his abs in the movie were indeed perfect.

But that doesn't necessarily make them the best. On a recent episode of the Korean "Dynamic Gym" show, trainers voted actor Kwon Sang Woo, star of "Queen of Ambition" and of the upcoming drama "Medical Top Team" as having the best actor abs. Trainer Kim Seung Hyun said, "There are many muscular men, but in abs, Kwon Sang Woo is the best."

With the obligatory shower or swimming pool scene featured in so many kdramas, actors have to work hard to stay in top shape. Here are a few kdrama actors whose workouts deserve a mention or maybe even applause:

So Ji Sub: The star of the cyber detective story "Phantom" will soon appear as a cynical boss in "The Master's Sun. The actor says he actually enjoys working out. He swims and lifts weights, exercising whenever he gets the chance.

Gong Yoo: The "Coffee Prince" and "Big" star thinks its more effective to exercise before you eat, but he fits workouts in whenever his filming schedule permits. The star, who recently played a client on "Dating Agency: Cyrano," also diets if a role requires him to take his shirt off. He plays basketball for fun.

Song Seung Hoon: He doesn't smoke, he only drinks occasionally and he exercises a lot to maintain his good looks and muscular build. He bulked up for his role as the thug-turned-successful businessman in "When A Man Loves." But then he also looked great in "My Princess" and is not above posting shirtless photos on Facebook and Twitter.

Chansung: Although it was not his first opportunity to show off his abs, the 2PM singer did get to flash them for the first time on a kdrama when he played a rookie agent in "Level 7 Civil Servant." Chansung showed how hard he works out by punching a sandbag. The production team said he had the talent to go head-to-head with professional boxers.

Taecyeon: Chansung's fellow 2PM member was chosen by the music industry as having the best kpop abs. He did wow Suzy's character with them in "Dream High" when she surprised him after a shower. To achieve his perfect physique, trainers recommend fast walking, plus back, shoulder and chest workouts, as well as aerobics for more an hour every day.

All that exercise is hard work but fans do appreciate the results.