The number one question most people ask when they start Taekwondo is, how do I become more flexible?
Although genetics certainly can play a roll in a student's flexibility, there are plenty of things you can do to increase your flexibility and range of motion.
Creating a regular stretching routine is the first step, followed by repetitive kicking exercises . It will not only improve flexibility but also strengthen and elongate the muscles and tendons, as well as build the strong core necessary for balance.
https://www.youtube.com/watch?v=RgIYeCbDpz8