The aim of this study is to examine the effects of plyometric training on biceps femoris longus (BFl) and vastus lateralis (VL) muscle architecture in individuals with anterior cruciate ligament reconstruction (ACLR). Individuals will be randomly placed into training and control groups. Measurements of muscle architecture will be taken bilaterally from BFl and VL muscles by means of an ultrasound device. Functional performance will be evaluated with the International Knee Documentation Committee score and the single leg jump test. Following the initial evaluations, individuals in the training group will receive plyometric training. Evaluations of muscle architecture and functional performance will be taken again from the individuals in the training and control groups at the end of the 4th and 8th weeks. The received ultrasound images will be calculated through the MicroDicom software. In-group and between-group comparisons will be analyzed using the Statistical Package for the Social Sciences program and appropriate tests.

Anterior cruciate ligament (ACL) injuries are common, especially in young individuals participating in rolling and jumping activities. After injury, many people undergo ACL reconstruction (ACLR) surgery. The aim of this study is to examine the effects of plyometric training on biceps femoris longus (BFl) and vastus lateralis (VL) muscle architecture (fiber length, penation angle and muscle thickness) in individuals with ACLR. Individuals who have undergone ACLR in this study, which is designed as a parallel group randomized controlled study, will be randomly placed into two different groups, the training group and the control group. Imagery ability, self-efficacy and motivation will be evaluated with various questionnaires and scales in order to compare the homogeneity of the groups. Measurements of muscle architecture will be taken bilaterally from BFl and VL muscles by means of an ultrasound device. Functional performance will be evaluated with the International Knee Documentation Committee score and the single leg jump test. Following the initial evaluations, individuals in the training group will receive plyometric training consisting of ten different exercises for 8 weeks, 3 sessions per week. In this training, individuals will not participate in a real plyometric training. Volunteers will watch videos to be prepared (action observation) and imagine them performing those exercises (motor imagery). Except for one session that will be applied every two weeks, all other trainings will be given on the basis of telerehabilitation via distance education tools. Cognitive fatigue at the beginning and end of the session; at the end of each session, the technical quality and efficiency of the training will be evaluated. Evaluations of muscle architecture and functional performance will be taken again from the individuals in the control and training groups at the end of the 4th and 8th weeks. The received ultrasound images will be calculated through the MicroDicom software. In-group and between-group comparisons will be analyzed using the Statistical Package for the Social Sciences program and appropriate tests.

Inclusion Criteria:

• Volunteers with unilateral anterior cruciate ligament reconstruction (ACLR)
• Volunteers using hamstring autograft in their ACLR
• Volunteers who have passed 1-5 years after their ACLR

Exclusion Criteria:

• Those who underwent same-side meniscus repair other than ACLR
• Those who have had revision surgery
• Those who had posterior cruciate ligament rupture in addition to anterior cruciate ligament
• Third-degree tears in the lateral or medial collateral ligaments
• Those with 2nd or 3rd degree strain injuries in hamstring and quadriceps muscle groups
• Those with a history of congenital, neurological, orthopedic, rheumatologic and cardiopulmonary pathology or anomalies,
• Those with serious systemic diseases

Relative Exclusion Criteria:

• Those with acute infection or pain
• Those with joint instability
• Those with a body mass index of 30 and above
• Those receiving energy supplements or ergogenic assistance during or during the 6-month period prior to work