Before we get into the nitty gritty, the meat of how the 3 star drill benefits your health, longevity..... and yes its internal aspects, we must mention one of its companion drills, one that is rarely seen anymore but is just as important... the Shin Star drill also known as Chi Geurk or Chi Geuk.
The first strike involves the crest of the shin itself. This exercise starts with a lap sau or nap sau strike and grab of the arms.
The leg is then swung around and back striking the side of the calf muscle
and around and back striking the other side of the calf muscle.
The Chinese martial arts utilize single leg stances, referred to as crane stances as an important bridging and defensive techniques. This drill conditions the lower leg to withstand strong impact and to deliver devastating leg strikes. It also works single leg stance balance and rooting. But, one of its most important results is the development of leg sensitivity and the ability to "bridge" with the legs much as you learn to do with the arm Kiu.
There are many other drills to strengthen other parts of the body used to strike, or to defend but the 3 star and shin star drill are the most essential.
Preparation for shin star is also essential and involves massage, herbs and preliminary exercises, according to Chinese methodology and tradition. These aspects must be learned from a knowledgeable instructor. And of course, Dit Da liniment is a must.