Every lesson we spend time working flexibility for every large group of muscles, over time with practise the muscles stretch and become more flexible. Not everyone can do the splits but you only push yourself as far as you can go and eventually over time your child will be able to do things they have never been able to do before for example touching their toes with ease. 

 

An old Martial arts saying

"Karate is just like hot water, if you do not consistently give it heat it will return to its tepid state"

 

This is same for flexibility, as you get older you will find that your not as flexible as you used to be, Here we practice consistently to avoid the tepid state.