First of all, it is the nervous system that will perceive the signal at the level of the hand.
Then the nervous system will process the information at the level of the central nervous system and then send it to the muscle to contract.
And finally, it is the skeleton that will move following the contraction of the stimulated muscle so that the hand away from the source of pain and stop the signal.
The principle of sequence involves appending more effort at every exercise to reinforce the muscles. You simply endeavor to perform more than you did the previous time