This study aimed to investigate the effects of stretching, strength, and plyometric exercise training programs, applied in addition to regular training, on jumping performance and knee valgus values in football players.

The sample of this study consisted of male football players from an under-19 (U-19) team based in Kayseri, Turkey. The inclusion criteria required participants to be male, aged 18 or older, actively competing in the U-19 category, free from any disabilities, and to have at least five years of experience as licensed football players. In 2024, ninety athletes from an amateur football club were invited to participate in the study. Participants were assigned to experimental and control groups using an unbiased sampling method. Groups were balanced based on pre-test results to ensure equivalence.

A true experimental design was employed, specifically the pre-test-post-test control group model. Jump tests, including the countermovement jump (CMJ), free-arm countermovement jump (CMJFREE), drop jump (DJ), squat jump (SJ), and horizontal jump, were conducted using the My Jump 2 application. The knee valgus test was performed using the My Jump Lab application, which enables markerless motion analysis by evaluating images recorded by a mobile device. This application provides valuable insights into injury prevention particularly in the lower extremities and supports the assessment of proper execution of technical movements.

The training program included strength, flexibility, and plyometric exercises, designed to reduce muscle strength imbalances while enhancing flexibility and plyometric performance. Since improvements in motor characteristics and muscle balance are expected to positively affect knee valgus angles, all components of the training program were implemented in combination. Strength training was carried out over eight weeks and included full-body, core, and lower extremity exercises. In addition, the anterior cruciate ligament injury prevention program developed by Hewett et al., which emphasizes plyometric training, was incorporated during the first six weeks in accordance with its prescribed duration. Stretching exercises were performed following strength training sessions throughout the entire eight-week period. The training program was administered exclusively to the experimental group and followed a consistent schedule and sequence. Training sessions were conducted three times per week for eight weeks, separate from routine football practices. Plyometric exercises were included once per week, and a minimum one-day rest interval was maintained between sessions.

Data were analyzed using SPSS version 27. The Kolmogorov-Smirnov test was used to assess the normality of data distribution. Repeated Measures Analysis of Variance (ANOVA) was applied for within-subject comparisons, while the Bonferroni test was used to determine the source of significant differences. Between-group comparisons were conducted using the Independent Samples t-test.

Inclusion Criteria:

• Being a football player playing in the U-19 football team
• Being a male
• Residing in Kayseri
• Be between 18-19 years old

Exclusion Criteria:

• Not being a football player playing on the U-19 football team
• Being a female
• Residence outside Kayseri
• Being outside the 18-19 age range

Male