Limbs must remain slightly bent when hitting. Both the arm or leg ,stay slightly bent to impact. Sanchin's power base must be set. There is a torquing of the body at impact. All this will take lots of practice. There will be lots of pushing of the strikes at first. Everything must come together for success. Striking in this manner will enable you to hit very hard from very close. Have a look at some hand strikes, and leg thrusts to detect this. May look easy. When you begin to practice this method, you'll find that it will take some time. Once you get it, you will be like a kid with a new toy.
https://www.youtube.com/watch?v=mOyZedk8-ww
https://www.youtube.com/watch?v=YahMRSsSnRQ