An exercise machine adjustable resistance system and method for efficiently varying the workout resistance for an exercise machine. The exercise machine adjustable resistance system and method generally includes a control unit in communication with a resistance adjustment system of an exercise machine and a biometric monitoring device used by an exerciser on the exercise machine. The control unit receives biometric data from the biometric monitoring device and sends a control signal to the resistance adjustment system to adjust the resistance of the exercise machine based on the biometric data received.