Hey Guys, this will be my first post here. I'm fairly new as i've only trained shotokan karate for nearly a year now (just graduated 7'th kyu). I am one of these "small Guys". 169 cm tall weighting roughly 60 kg. During the classes in our dojo i always get to spar with much heavier and taller Guys at my own age (i'm 28) or older. I tend to be much quicker in both tzuki's and geri's. In my Humble opinion i think it is of course your physics, but the execution plays such a huge part. I use my heavybag several times a week. I often train my tzuki's to improve the speed, accuracy and execution. I don't know if you Guys have experienced the same. But i've tried some times now, where i Struck with the proper execution and full focus (kime). All these Things brought so much power that i was shocked.. my heavybag flew off from 3 of the chains, dingling in just 1. I've never been concidered strong or "buffed", far from. But with the proper technique and execution, it's simply amazing what you can do.