A powered strength trainer includes: a motor of a load element being a DC or brushless motor; a controller, provided for users to adjust current and signal of the motor through a microcomputer control panel, and control the torque, vibration frequency and amplitude of the motor, such that the motor can produce a pulling force, a resistance and a vibration force at the same time, and a vibration waveform can be selected as needed, and a movement path sensor is provided for feeding back a position and determining a positive and negative rotation, and a curved load control is used for compensating a load current appropriately, and allowing users to obtain a smooth and real-world setting. A planar spiral spring drives a winch to rewind the steel wire to prevent the steel wire from falling out during a power disconnection or a power failure.