# Evaluation of Commercial Ropes Applied as Artificial Tendons in Robotic Rehabilitation Orthoses
## 4 Discussion  
Results of the volunteers grip force measures confirm that they have a strength lower than that of typical individuals. Normative data indicate that healthy individuals had an average dominant hand grip force of 28.4 \(\pm\) 9.7 kgf for women and 40.3 \(\pm\) 14.3 kgf for men [41]. The change in post-stroke individuals grip force is related to the motor deficits found after the brain injury, which result from the injury to the upper motor neurons that control the distal and proximal muscles, generating a decrease in the activation of some muscle groups [42]. In addition, there is the presence of spasticity, could cause postural changes in the upper limb, which, if not corrected it generate deformities, affecting even the joints and muscles viscoelastic properties and the tendons integrity. Therefore, based on the studies of [PERSON] et al. [43, 44], we can use a high resolution ultrasound as an alternative to check these phenomena and select the most suitable cable to be used in robotic orthoses.  
It can be noted in the fishing line tensile strength test (Figure 4), that there is a variability in its behavior, presented maximum traction strength below than the desired. In addition to inconsistent behavior, it is difficult to handle and could difficulty in properly adjusting tendons before orthosis operation.  
The D'Addario (85/15 bronze) guitar strings (Figure 5), despite their smallest strain, suffered some damage with the application of low force, once their constitution was related to the sound and not to the material resistance. Its structure broke internally or suffered cracks with low loads, which can be seen with a simple visual inspection.  
The paragliding rope showed the highest tensile strength among the tested ropes (Figure 6), breaking through the external structure destruction, with a smoothly break.  
Thus, given the analysis of data obtained in the tests performed with different ropes, the conclusion was that the most suitable for use in robotic orthosis is the paragliding rope which meets the pre-established criteria of: strength, diameter and cost. (DuPontTM Kevlar(r)). The rope presented an easy handling and greater security due to values of resistance to traction superior to the other ropes, and due to its form of rupture, since the others present a whip when broken.  
The pilot test confirmed the consistency and precision in the opening angle using this rope, showing the satisfactory use as an artificial tendon in robotic orthoses. This system makes it possible to efficiently open and close the post-stroke individuals fingers, since a significant proportion of individuals with physical sequel resulting from stroke, remains with problematic or unsatisfactory manual function return [45]. With the use of artificial tendons in the orthosis, there is an increase in functional skills, facilitating the daily activities performance, such as reaching, picking up and holding objects, using tools such as a cell phone, eating, dressing and performing personal care in a general way. This significantly impacts the patient's life, improving his independence, self-esteem and life quality.