Chudan Oi Zuki - Lunge Punch to the Chest Level

In Karate, chudan oi zuki is a very simple but very powerful punch. This punch is done in zenkutsu dachi, it is not a jab and it carries power but the secrete is in the stance (zenkutsu dachi). This is done by keeping power on one leg in front which is going to carry all the wait while you trust forward without standing while the leg at the back moves, drawing a zig zag-like pattern on the floor, as the hand at the same side as the moving leg also thrusts sharply to the opponents chest or tummy (chudan).

The hand at the side of the Leg with load or your pivot (the one on the ground) serves as a target, therefore is withdrawn simultaneously as the punching hand jets forward. 

The waist also plays a very important role by twisting to adjust to the movement since you don't stand in zenkutsu dachi.