Rapid rate of contraction and relaxation in punch or kick.

The skillful karate fighter is not only strong, but in order to initiate a punch or a kick can contract muscles with great velocity, and also relax rapidly, the rate of relaxation is very rapid. The karate expert must start power generation in the legs through the hips, and as they hips explode the core contract quickly to transmit the force to the upper body, initial pulse start with quick contraction, and than the core relax as the punch or kick increase the velocity until the impact and than to avoid energy leak a second contraction occur.

Initiate with very quick muscle contraction and a very rapid muscles relaxation to allow speed increase, and a second sharp pulse of muscles contraction to deliver the full power.

One must do this using the big muscles of the hips through the shoulders for power generation, while keeping the spine stable, to allow full transmission of power, (power is not generated at the spine) to avoid stress on spine and to allow the spine to be an anchor for the bigger muscles to be fully utilized.

Therefore the sequence of contraction is as important as the rate of contraction.

Smaller, inner stabilizer muscles contract first, than the bigger force production muscles.