# A Hand Motor Skills Rehabilitation for the Injured Implemented on a Social Robot
## 2 Related Works  
As stated in [1], conventional exercise programs follow the [PERSON] [2; 3] or [PERSON] [4] concepts, as well as the proprioceptive neuromuscular facilitation (PNF) principles [5]. On the one hand, [PERSON]'s method emphasizes the reduction of enhanced muscle tone before facilitating active movements by means of cutaneous and proprioceptive stimuli applied to the region of the target muscles. On the other hand, [PERSON]'s approach and PNF use maximal innervation of intact or less-paretic muscle groups to produce irradiation effects in more severely paretic synergistic muscle groups. Several studies have been carried out with some of these techniques [6; 7; 8; 9; 10]. However, none of these studies presented a suitable control group, so the benefit was difficult to extrapolate from spontaneous recovery. Additionally, they presented a lack of exercise strategies for the hand muscles. In [1], the authors investigated the effect of a specific training program focused on the performance of the basic movement parameters of the hand. They paid special attention to the identical repetition of movements, whose long-term benefits have been demonstrated in other studies with animals [11; 12]. The patient scores for the rehabilitation exercises were calculated according to the Rivermead Motor Assessment [13], a widely used technique to measure motor ability in stroke patients, and 24 out of 27 patients showed an important improvement according to this metric. In this study, they introduced control groups to ensure the impact of the specific repetitive motor training in motion improvement. In order to evaluate muscles' progress during the rehabilitation process, some rehabilitation exercises take advantage of surface electromyography (sEMG) electrodes [14; 15; 16; 17]. These wearable electrodes enable the professional in charge to analyze the muscular activities and muscular strength of a patient during each exercise [18; 19]. In some rehabilitation methods, with aim of having an interactive system and motivating patients with visual and audio feedback, during the process, sEMG analysis is incorporated into a 3D game [20; 21], virtual reality (VR) [22], and augmented reality (AR) [23]. In addition, there are algorithms that take sEMG signals as the input in order to compute [24] different low-level move ments of the muscles. Specifically, this paper introduces a method to perform movement identification of the upper limb: Abduction, adduction, flexion, extension, and abduction followed by arm to the front. In recent years, researchers have focused on robot-assisted neurorehabilitation in order to improve the performance of rehabilitation exercises. According to [25; 26], two main approaches have been used to design hand rehabilitation devices: End-effector and exoskeleton robots. End-effector-based robots are usually employed to simulate activities of daily living (ADLs), to train the hand and, eventually, the wrist function by only interacting with the distal segments of the fingers, that is, the fingertips or sometimes the middle phalanxes. The rest of the arm is not controlled by the robot, which may result in patients using undesired compensatory strategies, so it is common to provide a weight support in order to reduce the muscle fatigue produced by the distal limb [27; 28; 29; 30; 31; 32; 33]. These types of robots are prepared for hands of different sizes, so they can be easily adjusted for different patients. On the contrary, an exoskeleton consists of a mechanical structure that is mounted in parallel with the limb of the user in order to provide assistance, so each degree of freedom is locally aligned with the corresponding human joint [16; 17; 34; 35; 36; 37; 38; 39; 40]. The majority of hand exoskeletons aim to restore grasping function by helping patients open the hand or provide force augmentation to hold objects. They do not limit the natural joint movements of patients, but their design is far more complex and the adaptation process for new users is more difficult.