Background and Aim: Since many of people in their functional activities mostly place their knee joint in flexed position, the hamstring muscles tend to be shortened. On the other hand, shortness of these muscles affect the knee joint directly and the ankle and hip joints indirectly. It predisposes the individual to musculo-skeletal injuries. Thus, by early diagnosing and treatment of it, the tension may be decreased, the relaxation increased and the development of injuries can be prevented. In order to achieve this goal, various stretching techniques are used. The purpose of this study is to compare the effects of static and PNF stretching on shortness of hamstring muscles in 18-30 years young women.

  Materials and Methods: Thirty 18-30 years old nonathletic women without any history of pathology in hip, knee or back were selected. They were divided into three groups with 10 women in each group(static stretch, PNF stretch and control). The two stretch groups were received stretching program five days every week for three weeks, while the control group was not.

  Results: The range of knee extension of both groups of static and PNF stretching increased (p<0/05). However there was no significant difference between these two groups (p>0/05).

  Conclusion: Employing of both methods (static and PNF stretching) increase the hamstring muscles flexibility. However there was no significant difference between two groups in increasing rang of knee extension.

  Key words: Hamstring muscles, static stretching, PNF stretching