In the literature, the evidence regarding the effects of different static stretching times on elasticity is very limited, and the evidence on the effects on flexibility varies. Although 10 to 30 seconds of static stretching is said to be effective, studies on which duration is effective for which muscle group are quite limited. Based on these, the aim of this study is to examine the effects of stretching exercises of different periods on muscle elasticity to be applied to thin and thick muscle groups. In order to evaluate its effectiveness, assessment of evaluation of muscle flexibility, active-passive range of motion were being applied.

Flexibility, the most important component of physical fitness, is defined as the maximal range of motion occurring in the joint or joint group. Elasticity is the ability of the structure to change its shape and size with the effect of force and to return to its previous position when the force is removed. These two components are also very effective on strength, agility, balance, speed, coordination and proprioception, which are other components of physical fitness. It is very important in reducing stress and tension, relieving muscle cramps, muscle relaxation, body fitness, reducing risks of injury and pain, regular sleep and daily life activities. Good levels of this increase the efficiency of the movement.

Different stretching protocols are applied in traditional rehabilitation to increase these levels. Static stretching, which is one of these stretching protocols, is known to prevent injuries and benefit performance as a result of increasing the range of motion. It is a type of stretching that minimizes the risk of injury as well as easy application. However, stretching times that will change the elasticity and flexibility of a large-thick muscle and a thin-long muscle are different. In the literature, the evidence regarding the effects of different static stretching times on elasticity is very limited, and the evidence on the effects on flexibility varies. Although 10 to 30 seconds of static stretching is said to be effective, studies on which duration is effective for which muscle group are quite limited.

Based on these, the aim of our study is to examine the effects of stretching exercises of different periods on muscle elasticity to be applied to thin and thick muscle groups. The study will be carried out on healthy, sedentary people aged 20-45 years. People who agree to participate in the study will be randomly divided into two groups. Static stretching will be applied to the hamstring and gracilis muscles of one group for 10 seconds while static stretching will be applied to the other group for 30 seconds. Static stretching exercises will be applied 8 weeks, 3 days a week, 3 times a day in 10 repetitions. On the dominant legs of the participants will be evaluated muscle elasticities with Myoton, muscle flexibility with flexibility tests, joint range of motion with goniometer. As a result of our thesis study, the investigators aim to find out how many seconds of static stretching will be more effective in different muscle groups, how different stretching times will change the muscle elasticity in different muscle groups, and thanks to this information, the investigators will be more successful in rehabilitation.

Inclusion Criteria:

• Being between the ages of 20-45
• Have not had any disability or surgery in the past 6 months
• Not exercising regularly in the last 6 months
• No neural signs
• To participate regularly in the study

Exclusion Criteria:

• Exercising regularly in the last 6 months,
• Having any disability or surgery not allowing stretching exercise,
• Having hip-knee-waist problem
• Having comorbidities not allowing stretching exercise such as inflammatory rheumatic disease, orthopedic and neurological disease

The participants of the study will be included in the stretching exercise program, but the participants will not have information about which group the participants belong to.