Seon Hwa has has considerable amount of muscle mass compared to her weight

In the episode of MBC’s We Got Married that aired on February 23, ZE:A’s Gwang Hee and Secret’s Seon Hwa visited a gym for workout.
Before starting workout, the couple had their physical checkup.
Seon Hwa, who is known to have regularly exercised, revealed her weight—47.3kg. What’s more, her physical report showed that her bones and muscles account for more than half of her weight. Her onscreen hubby was surprised to learn that she is even more fit than she looks.
That was not all. Seon Hwa even showed off her athletic ability, which she has acquired through regular workout. The singer lifted 40kg weight, showing a well-balanced posture.

• Source: Starnews