#### 1.1.2 Fes  
The rehabilitation of stroke patients is a comprehensive process that involves improving muscle strength and training gait using various methods and devices, including functional electrical stimulation (FES) [20]. FES is a supplementary therapy in rehabilitation guidelines. It benefits patients suffering from central motor neuron pathologies by leveraging brain plasticity to restore the ability to perform voluntary movements [21]. FES is an integral part of stroke rehabilitation guidelines, serving as an adjunct technology with significant benefits for patients with such conditions [22]. It is widely recognized and utilized in medical rehabilitation [23], and FES sessions entail the precise application of electrical stimuli to the muscle at motor points. These stimuli are often synchronized with specific physical activities tailored to the patient's needs, such as walking, cycling, or arm exercises [24]. The current can be delivered to the muscles through various types of electrodes that can operate on the surface, percutaneousally, or subcutaneously, thus producing muscle contraction through the depolarization of motor units. Functional electrical stimulation is divided into two distinct categories: assistive FES, which is used for the complete replacement of motor function, and therapeutic FES, which is used for rehabilitation purposes [21]. Therapeutic FES has a wide range of applications, mainly benefiting the rehabilitation of patients with central motor neuron damage. Additionally, it plays a crucial role in preventing muscle atrophy and maintaining the health of the muscular system. Assistive FES, however, is designed to restore motor function in patients with central neuron syndrome by completely replacing motor signals [22]. Nerve stimulation is the preferred method for FES due to its significantly lower electrical charge. This reduces the risk of burns or other tissue damage and instills trust in the procedure's safety [23]. Percutaneous FES, a technique involving intramuscular electrodes, offers unparalleled precision and control, even of deeper muscle structures. While it requires surgical procedures with risks such as postoperative infection and higher costs, it also provides several advantages. Implantable electrodes are more efficient and reliable, and their configuration is more precise compared to systems using surface electrodes. However, it is important to note that surface electrodes, while easier to configure, may be less accurate. This comprehensive view allows the audience to make informed decisions about the best approach for their patients [25]. Implementing the most effective rehabilitation program is a significant challenge for individuals who have had a stroke. However, effective therapeutic strategies, especially those incorporating new rehabilitation approaches, have not been thoroughly explored. The combination of VR and FES in stroke rehabilitation is grounded in their complementary strengths, offering a promising approach to addressing stroke survivors' persistent challenges. The necessity for this study arises from the need to enhance rehabilitation outcomes by leveraging the benefits of both VR and FES, particularly for upper limb rehabilitation, where motor deficits, sensory disturbances, and altered muscle tone significantly impact functional abilities and quality of life. With its immersive and engaging environments,VR encourages greater patient engagement and motivation by making repetitive exercises more enjoyable and mentally stimulating, which is crucial for long-term rehabilitation success. However, VR alone may not be sufficient for restoring motor function, especially in severe cases where muscle activation is compromised. Conversely, FES directly stimulates muscle contractions through electrical impulses, promoting muscle strength and neuroplasticity, which are essential for regaining voluntary movement.