Northern Shaolin #4, Penetrating Heart, teaches a number of new techniques including the deadly Penetrating Heart Punch. Penetrating Heart has few flying kicks, or leaps, compared to the other Northern Shaolin forms. It still has them, just, not as many. Penetrating Heart Form does however, introduce the Flying Toe, Crescent Kick, and the Hopping Stomp Kick. The stomp kick is a powerful, practical kick. It is easy to knock someone down, or back a long ways, with the stomp kick. The hop makes it deceptive and closes the distance after the opponent has stepped back to avoid it.
Instead of kicks, this form emphasizes many strong punching techniques and low stance work. This form really builds thigh strength with its low stances. Penetrating Heart also develops the general nimbleness of the legs with its many unique hopping, skipping, or jumping techniques.
In particular, there is a very, very low empty stance that is used. Once we leap into and out of this stance rapidly while throwing a rear kick in the air on the way out. Two times this super low empty stance is used we throw High Toe Kicks from it and then hop forward into stomp kicks.
In the center of the form is one section of about 15 moves that is repeated twice. This repetition makes this form relatively quicker to learn than the other short forms. However, the stance work and new hand techniques in repeated section are not easy. Therefore, this form takes a bit of effort to smooth out. Not everyone is good at high kicking and some people are just really suited to throwing huge powerful punches. So some people just love this form. This is a good form if you like strong hand techniques.
I think this is one of the best looking forms in terms of the balance of its choreography. I also like the ending. The ending is very fast and agressive and then suddenly stops.