Kate revealed that she and Princess Charlotte can do the splits.
The revelation was made during a visit to a leisure and fitness center in Port Talbot.
Kate told children from Tywyn Primary School about her hidden talent.
Princess Charlotte is interested in gymnastics, according to Tim Lawler.
William and Kate took part in a spin class challenge at the leisure center.
Kate won the 45-second race and was given a gold cup.
The royal couple visited South Wales to champion mental health initiatives.
William was announced as the new patron of the Wales Air Ambulance charity.
This is the first Welsh patronage to be announced for William since he became the Prince of Wales.