In recent years, advanced electromechanical technologies have been progressively built into equipment for physical exercise to improve the safety and effectiveness of fitness and sport training programs and rehabilitation interventions. One of the most interesting innovations concerns strength training machines that use a motor and an electronic management system to generate adaptive resistance adjustments in response to the kinematic parameters of movement. These devices enable a number of advanced strength training modalities, not only can simulate external resistance of different kinds (i.e. gravitational, elastic, viscous, isokinetic, etc.) but can also manipulate different levels of inertial force. This new training modalities can be designed to closely reproduce the kinematic and kinetic patterns occurring during different kind of applications, rehabilitation included, but also to open new scenarios to improve explosive power for sports performance.