Physical training is just like normal teaching. You are programming a neural network. But the input vectors are not ideas, they are paths carved out of spacetime. This gives opportunities for physical feedback if the training is done right.

Internal feedback when attacking/striking is detected by two things: the amount of force which the student feels on recoil (i.e. every action has an equal and opposite reaction), and the perceived effect which the student sees on the enemy/opponent. External feedback for striking should be communicated to the student by the teacher, both recoil and enemy effect.

For blocking, the student should measure the striking force felt for internal feedback. External feedback quickly becomes unnecessary for blocking, the student knows well how hard it has been hit. But the initial external feedback provides calibration for the student, so it is necessary for all but the best and most experienced students.

This is why all training after initial footwork and sequencing should be full contact sparring. Otherwise there is no way to effectively provide floating point feedback.