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.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
NONE
Enrollment
90
Strength training was implemented for eight weeks, including full-body, core, and leg exercises.
Stretching exercises were performed after strength training for the entire eight-week period. The training was administered exclusively to participants in the experimental group, following a consistent schedule and sequence. The program was conducted three days a week for eight weeks, separate from regular football training.
Plyometric exercises were included only one day per week, and a minimum one-day rest period was maintained between training sessions.Since this program was originally 6 weeks long, it was implemented in the first 6 weeks of the study's implementation process.
Erciyes University
Talas, None Selected, Turkey (Türkiye)
Change in Countermovement Jump Height (CMJ) Measured in Centimeters
CMJ test was performed using the My Jump 2 app. The jump height (in cm) was recorded in 3 separate measurements and the average was used for comparison.Unit of Measure: Centimeters (cm)
Time frame: Each participant in the study was evaluated by taking 3 separate measurements before starting the study, at the end of the 4th week of the study, and at the end of the 8th week of the study. The total evaluation process was completed within 8 weeks.
Change in Free Arm Countermovement Jump Height (CMJFREE) Measured in Centimeters
CMJFREE test was performed using the My Jump 2 app with free arm movement. Values were averaged from 3 trials.Unit of Measure: Centimeters (cm)
Time frame: Each participant in the study was evaluated by taking 3 separate measurements before starting the study, at the end of the 4th week of the study, and at the end of the 8th week of the study. The total evaluation process was completed within 8 weeks.
Change in Drop Jump Height (DJ) Measured in Centimeters
DJ test was performed using the My Jump 2 app. Jump height (cm) was measured and averaged across 3 attempts.Unit of Measure: Centimeters (cm).
Time frame: Each participant in the study was evaluated by taking 3 separate measurements before starting the study, at the end of the 4th week of the study, and at the end of the 8th week of the study. The total evaluation process was completed within 8 weeks.
Change in Squat Jump Height (SJ) Measured in Centimeters
SJ test was performed using the My Jump 2 app. Jump height (cm) was measured and averaged across 3 trials.Unit of Measure: Centimeters (cm)
Time frame: Each participant in the study was evaluated by taking 3 separate measurements before starting the study, at the end of the 4th week of the study, and at the end of the 8th week of the study. The total evaluation process was completed within 8 weeks.
Change in Horizontal Jump Distance Measured in Centimeters
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Demographic tests were applied to determine the height, weight and BMI values for the identification of the participants.
Jump tests (CMJ, CMJ Free, SJ, DJ, Horizontal Jump). Three different measurements were taken at three different times.(Before starting, end of week 4 and after completion of week 8).
It was conducted to determine the right and left knee valgus values of the participants.Three different measurements were taken at three different times. (Before starting, end of week 4 and after completion of week 8).
Horizontal jump test was performed manually. Jump distance (cm) was recorded and averaged across 3 trials.Unit of Measure: Centimeters (cm)
Time frame: Each participant in the study was evaluated by taking 3 separate measurements before starting the study, at the end of the 4th week of the study, and at the end of the 8th week of the study. The total evaluation process was completed within 8 weeks.
Change in Knee Valgus Angle Measured in Degrees
Knee valgus angle was assessed using the My Jump Lab app. Degree values were measured from 3 trials and averaged for each time point.
Time frame: Each participant in the study was evaluated by taking 3 separate measurements before starting the study, at the end of the 4th week of the study, and at the end of the 8th week of the study. The total evaluation process was completed within 8 weeks.