Mobile and attachable electrical resistance system for exercise machines and free-weight equipment

(canceled)

(canceled)

A method for retrofitting an exercise machine having exercise interface connected to a native resistance source comprising:

• supplying a resistance source configured for applying an adjustable resistance to movement between a force transmitter and a base of the resistance source and a controller for changing said resistance;
• anchoring said base to the exercise machine;
• connect said exercise interface to said force transmitter.

15-19. (canceled)

A system for exercise comprising:

• a plurality of exercise machines each of said plurality of exercise machines including a variable resistance source supplying a resistance to an exercise interface, a wireless transmitter and a controller controlling the resistance of said variable resistance source and receiving data from said variable resistance source;
• and
• a personal computing device of a single trainer in wireless contact with said plurality of exercise machines and whereas said personal computing device is configured to receive output of said variable resistance source and to control a resistance of said resistance source.

(canceled)