I was witness today to some truly remarkable power generated by one of my yellow belts as he's preparing for his grading next week -- off the humble front lunge punch.
Beginners typically time the punch with the step of the leg. Meaning as the leg goes forward in a 'step', the hand gets fired off at the same speed. As they progress, they then feel the expectation to strike harder, resulting in upper body tension. There's a lot of muscle tension that gets transmitted into the target through shoulder rotation. But pure power is lost.
What the practitioner needs to focus on to punch as hard as a black belt is ... the leg sprints as fast as possible whilst the body and the hand stays 'as is'. Only just before the foot lands on the floor, then you build up the muscle tension to fire off a punch. At the point of impact, the body 'locks up' to transmit the power of the legs into the arm.
My wonderful yellow belt after knocking his partner (holding a striking mitt) back 2 feet said that the punch was much more effortless than his strikes earlier in the morning! Can you imagine what would occur if you really tried to put power into something like that? Wow!
The Jon Alster Lunge Punch