<prompt> The force of muscle contraction can be increased by all of the following exceptIncreasing the frequency of activation of motor unitsIncreasing the number of motor units activatedIncreasing the amplitude of action potentials in the motor neuronsRecruiting larger motor units  <response>: The amplitude of action potential cannot be increased as it follows All or none law. Force of contraction can be increased by increasing the number of motor units involved in contraction, by increasing the frequency of activation of motor units or by recruiting larger motor units. 