1.    Introduction
Stretching and strengthening exercises are an important part of treating ankle diseases and problems. In many lesions of the lower limb, the ankle has limited movement and needs rehabilitation. After the ankle is injured, the exercises in person to perform daily activities. These exercises restore the lost energy of the ankle.
Various training methods have been used to improve ankle instability and change the kinematics and kinematics of the lower limb. In this regard, in the study of Kordi et al. the results showed that both hopping and balance strengthening exercises improved the angles of dorsiflexion, inversion and knee flexion in the initial foot contact during running in athletes. However, hopping exercises work better in improving the knee flexion angle in athletes with functional ankle instability (1). In Freeman et al’s study,  the results showed a significant difference before and after the training program, between the average scores of the parameters of the selected lower limb motor variables, in the experimental group (2).
Past studies have shown that people with functional instability of the ankle experience kinematic and kinetic changes of the lower limb. Therefore, it is very important to determine the effectiveness of different types of treatments for this condition. However, little research has been done in the field of finding the appropriate treatment method for people suffering from this condition. Also, researchers have not yet reached a general agreement about specific treatment methods that are approved by the majority, which is due to the specific complications of this disease and different treatment methods. According to our knowledge, so far there has been no study comparing the effect of leg muscle stretching exercises on kinematic and kinetic indicators of people with ankle instability, so the present study aims to answer the question os whether two types of leg muscle stretching methods have positive impacts on a selection of kinematic and kinetic indicators of the wrist in girls with ankle instability pain.
2.    Methods
The current study was conducted on human society, it is an applied and semi-experimental research that has the code of ethics with the number IR.IAU.ET.REC.1400.020 from the Islamic Azad University, Tehran East Branch, and with two experimental groups and one control group with the Pre-test-post-test design. The statistical population of this research includes women with ankle instability problem, 20-30 years old, who have referred to Firouz Gar and Meiri Hospital. 24 people were selected as a statistical sample and were randomly assigned to the group of functional stretching exercises (8 people). hyper functional stretching (8 people) and control (8 people). Kinematic and kinetic indicators were measured in all the pre-tests, then the subjects in the experimental group of functional stretching exercises (8 people) performed hyper-functional stretching for 6 weeks, four sessions per week and 45 seconds per session for each movement pattern for both legs. It was done under the supervision of the researcher and the desired tests were performed again in the post-test phase. After the pre-test evaluations, intervention groups underwent super functional exercises for six weeks, four sessions per week and 45 seconds per each movement pattern for both legs and a total of 15 minutes per training session. And then the desired indicators were measured again for both groups. At first, the dorsiflexion and plantar flexion and the ground reaction force were measured from the subjects in the physical education research institute using motion analysis cameras and force plates. Then the subjects underwent stretching exercises for six weeks, and after six weeks, the amount of dorsiflexion and plantarflexion and ground reaction force were calculated again.
3.    Results
The results of the paired or dependent samples t-test regarding the difference between the mean dorsiflexion angle, plantarflexion and ground reaction force showed that there is no significant difference in the variables investigated in the pre-test and post-test of the control group. On the other hand, the results of the paired or dependent samples t-test regarding the difference between the pre-test and post-test averages of the experimental group showed that there is a significant difference between the mean dorsiflexion angle, plantarflexion and ground reaction force of the pre-test and post-test of the experimental group.
4.    Conclusion
The results of the research showed that six weeks of functional stretching exercises have a significant effect on the degree of ankle dorsiflexion in girls with ankle instability pain. The results indicated a significant increase in the average angle of dorsiflexion (4 degrees). These findings are in line with the studies of Cornwall et al. (1999) and McLean et al. (2012) (3, 4). The findings of the present study on the increase of ankle dorsiflexion range of motion in the group of functional stretching exercises confirm that the range of motion of dorsiflexion increase the effect of stretching exercises. It also showed the superiority of functional stretching exercises in comparison to extra functional stretching exercises. This finding of the current research regarding the increase in dorsiflexion of the ankle is in line with the findings of Johnson et al. (2009). By performing functional stretching exercises, in fact, with the increase in dorsiflexion resulting from the functional stretching exercise program, there is no need to maintain the posture (5). The lack of locking and misalignment of the midtarsal joint is not excessive, which creates a normal mechanical condition in the joint and improves the resulting elastic energy for patients with ankle instability. This fact is in line with the results of the present research and is also in line with the results of researchers such as Lederman (2013) (6).

Ethical Considerations
Compliance with ethical guidelines
There were no ethical considerations to be considered in this research.
Funding
This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors.
Authors' contributions
All authors equally contributed to preparing article.
Conflicts of interest
The authors declared no conflict of interest.