The speed of operating structure of an exercise machine is sensed and rotates a worm gear interconnected to a reduction gear assembly to rotate a driver at a preselected rate. The driver is interconnected to drive a cam surface upon which a cam follower rides to in turn operate a pivoted lever. The lever is interconnected to transmit the movement of the cam follower to operate the resistance means of the exercise machine to increase or decrease the resistance being applied to the operating structure of the exercise machine.
