Answer:
The assessment of the muscles' health and the motor neurons (the nerve cells controlling the muscles) is determined by the procedure called Electromyography aka EMG, which identifyes nerves/muscles issues and also the quality of the signal transmission between them; like when the units in a contraction increase, correlates with the increase in the force of contraction. In this particular case of the EMG lab, the subject will squeeze to 1kg of force.
