Contents I. Introduction
Millions of people around the world lose the ability to perform motor functions after central nervous system lesions. Conditions such as stroke and spinal cord injury result in the impairment of motor function in upper or lower extremities [1]. Upper limb impairment is a prevalent after-effect of stroke and results in either lack of fine motor control or loss of functional movement. A report issued by the Royal College of Physicians in 2012 revealed that 70% of stroke patients suffer from a disorder of upper limb functionality [2]. An impairment in the upper limb, especially the hand, makes it troublesome for the individual to perform daily life tasks such as grasping, eating, and drinking, greatly affecting the quality of life. The patient can lose their independence and become dependent on palliative care given by attendants. To overcome or reduce the after-effects of the disability, patients commonly undergo rehabilitation therapies. The aim of the rehabilitation process is to make the life of a paralysed individual comfortable and independent. The rehabilitation therapy helps the patient to regain control over the lost motor movements. Functional electrical stimulation (FES)-based rehabilitation systems provide a potential approach to realize effective restoration of upper limb movements. In FES systems muscles are contracted by stimulating the motor neurons with low-level electrical pulses. The short bursts of electrical pulses help to generate an action potential in motor neurons required for the contraction of muscles. In order to avoid convulsive movements, the electrical pulses should stimulate the minimum number of action potentials required for a continuous contraction. It is to be noted that motor nerves should not be damaged in the muscle fibres due to injury, for the stimulation to be effective [3].
