<prompt> The force of muscle contraction can be increased by all of the following except:Increasing 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>: Action potential follows an all or none law. When sufficient amplitude is reached to produce a motor response, increasing the amplitude fuher will not have any effect on the motor response. Ref: Review of Medical Physiology by William F Ganong, 19th Edition Page 70 ; Biomechanics and Biology of Movement By Benno Maurus Nig, Page 275. 