A power assistive device for hand rehabilitation that provides training of a combined movement of finger flexion-extension and forearm supination-pronation to a user, the power assistive device comprising: a hand brace that in use attaches to a hand of the user and that includes: a plurality of finger driving units and that attach to fingers of the user; a plurality of actuators that connect to the finger driving units and that actuate the finger driving units; a base that removably connects to the hand brace and that includes: a supporting structure that is located on a proximal end of the base and that supports a forearm of the user; the power assistive device being characterized in that: the hand brace further comprises a plurality of force sensors (1302A and 1302B) that connect to the finger driving units and the bottom of the hand brace and detect force signals generated by movement of the hand brace; the base further comprises a forearm rotator that abuts the supporting structure and that includes a plurality of C-shaped tracks formed along an inner surface of the forearm rotator; a rotatable platform that moves along the C-shaped tracks and that in use receives a forearm of the user; and a mounting platform that connects to and extends from a distal end of the rotatable platform and that removably mounts the hand brace onto the base; and the power assistive device further comprises an electromyography sensor (402A and 402B) that in use attaches to either or both of an upper arm and a forearm of the user and that senses EMG signals generated by movement of the upper arm or forearm of the user; and a processing unit that communicates with the hand brace and the EMG sensor (402A and 402B) wherein the EMG signals and the force signals are received and analysed by the said processing unit to determine an onset time of muscle dynamics of the upper limb of the user. a hand brace that in use attaches to a hand of the user and that includes: a plurality of finger driving units and that attach to fingers of the user; a plurality of actuators that connect to the finger driving units and that actuate the finger driving units; a plurality of finger driving units and that attach to fingers of the user; a plurality of actuators that connect to the finger driving units and that actuate the finger driving units; a base that removably connects to the hand brace and that includes: a supporting structure that is located on a proximal end of the base and that supports a forearm of the user; the power assistive device being characterized in that: the hand brace further comprises a plurality of force sensors (1302A and 1302B) that connect to the finger driving units and the bottom of the hand brace and detect force signals generated by movement of the hand brace; the base further comprises a forearm rotator that abuts the supporting structure and that includes a plurality of C-shaped tracks formed along an inner surface of the forearm rotator; a rotatable platform that moves along the C-shaped tracks and that in use receives a forearm of the user; and a mounting platform that connects to and extends from a distal end of the rotatable platform and that removably mounts the hand brace onto the base; and the power assistive device further comprises an electromyography sensor (402A and 402B) that in use attaches to either or both of an upper arm and a forearm of the user and that senses EMG signals generated by movement of the upper arm or forearm of the user; and a processing unit that communicates with the hand brace and the EMG sensor (402A and 402B) wherein the EMG signals and the force signals are received and analysed by the said processing unit to determine an onset time of muscle dynamics of the upper limb of the user. the hand brace further comprises a plurality of force sensors (1302A and 1302B) that connect to the finger driving units and the bottom of the hand brace and detect force signals generated by movement of the hand brace; the base further comprises a forearm rotator that abuts the supporting structure and that includes a plurality of C-shaped tracks formed along an inner surface of the forearm rotator; a rotatable platform that moves along the C-shaped tracks and that in use receives a forearm of the user; and a mounting platform that connects to and extends from a distal end of the rotatable platform and that removably mounts the hand brace onto the base; and the power assistive device further comprises an electromyography sensor (402A and 402B) that in use attaches to either or both of an upper arm and a forearm of the user and that senses EMG signals generated by movement of the upper arm or forearm of the user; and a processing unit that communicates with the hand brace and the EMG sensor (402A and 402B) wherein the EMG signals and the force signals are received and analysed by the said processing unit to determine an onset time of muscle dynamics of the upper limb of the user.