RELATIONSHIP OF LEG STIFFNESS AND ISOKINETIC STRENGTH ON SQUAT AND COUNTER MOVEMENT JUMP IN ADOLESCENT SOCCER PLAYERS

Öz

Dikey sıçrama performansı, futbolcularda alt ekstremite kas gücünün önemli bir göstergesidir. Skuat sıçrama (SJ), konsantrik kuvveti yansıtırken, karşı hareketli sıçrama (CMJ) esneme-kısalma döngüsünün (SSC) verimliliğini değerlendirir. Diz izokinetik kuvveti ve bacak sertliği gibi biyomekanik faktörlerin sıçrama performansını etkilediği bilinse de adölesan dönemindeki yordayıcı rolleri belirsizliğini korumaktadır. Bu çalışma, adölesan erkek futbolcularda farklı açısal hızlardaki (60°/s ve 180°/s) izokinetik diz kuvveti ve bacak sertliği değerlerini kullanarak SJ ve CMJ performansını tahmin etmek için regresyon modelleri geliştirmeyi amaçlamıştır. Otuz dört erkek adölesan futbolcu; SJ, CMJ, bacak sertliği ve izokinetik diz fleksör ve ekstansör kuvvet testine tabi tutuldu. İstatistiksel varsayımlar doğrulandıktan sonra, sıçrama yüksekliğinin yordayıcılarını belirlemek için ileri yönlü kademeli regresyon analizi uygulanmıştır. CMJ için, 180°/s hızdaki diz ekstansiyon kuvveti, performans varyansının %15,9'unu anlamlı bir şekilde açıklamıştır (β = 0,399, p = 0,019); bacak sertliği ise varyansı açıklamada minimal düzeyde katkıda bulunmuştur (%19,5). SJ için, 60°/s hızdaki diz ekstansiyon kuvveti en güçlü yordayıcı olmuş ve varyansın %12,5'ini açıklamıştır (β = 0,354, p = 0,040). Bacak sertliği veya diz fleksiyon/ekstansiyon kuvvetinin anlamlı bir etkisi olmaksızın, 60°/s ve 180°/s fleksiyon/ekstansiyon ile bacak sertliğinin bulunduğu son modeller CMJ için varyansın %23'ünü ve SJ için %22,8'ini açıklamıştır. Yüksek hızlı diz ekstansiyon kuvveti (180°/s) CMJ performansını daha iyi yordarken, düşük hızlı kuvvet (60°/s) SJ performansını daha iyi yordamaktadır. Bacak sertliğinin izokinetik diz değişkenlerine göre önemli bir yordayıcı olmadığı görülmüştür. Bu bulgular, ergen futbolculara yönelik antrenman programlarının hıza özgü kuvvet gelişimini vurgulaması gerektiğini göstermektedir. Gelecek çalışmalar, ek biyomekanik faktörler ve performansa ilişkin başka faktörler dahil ederek parametrelerin tahmin gücünü artırabilirler.

Anahtar Kelimeler

• skuat
• karşı hareketli sıçrama
• futbol
• izokinetik

RELATIONSHIP OF LEG STIFFNESS AND ISOKINETIC STRENGTH ON SQUAT AND COUNTER MOVEMENT JUMP IN ADOLESCENT SOCCER PLAYERS

Öz

Vertical jump is a important indicator for lower-limb muscular power in soccer players. The squat jump (SJ) indicates concentric strength, whereas the countermovement jump (CMJ) reflects the capacity of the stretch-shortening cycle (SSC). Although factors such as knee isokinetic strength and/or leg stiffness are known to affect jump performance, predictive roles of these factors during adolescence period remain unclear. This research was aimed to develop a regression model to predict SJ and CMJ performance in adolescent male soccer players, using isokinetic knee strength at different angular velocities (60°/s and 180°/s) and leg stiffness values. Thirty-four adolescent male soccer players participated in this study. SJ, CMJ, leg stiffness, and isokinetic knee flexor and extensor strength measurements were performed. After statistical assumptions tested, stepwise-forward regression analysis was performed to detect predictors of jump height. For CMJ, knee extension strength at 180°/s significantly reflected 15.9% of the variance in performance (β = 0.399, p = 0.019), while leg stiffness contributed minimally (%19,5). For SJ, knee extension strength at 60°/s was the strongest predictor, reflected 12.5% of the variance (β = 0.354, p = 0.040). The last model including 60°/s and 180°/s flexion/extension and, leg stiffness explained 23.0% and 22.8% of the variance for CMJ and SJ, with no significant effects from leg stiffness or knee flexion strength. High-velocity knee extension strength (180°/s) was more predictive for CMJ performance, whereas low-velocity strength (60°/s) better predicted SJ performance. It was observed that leg stiffness was not a significant predictor compared to isokinetic knee variables. These findings suggested that training programs for adolescent soccer players should emphasize velocity-specific strength development. Future studies could incorporate additional biomechanical and performance-related factors to increase prediction accuracy of the parameters.

Anahtar Kelimeler

• squat
• countermovement
• football
• isokinetic

Kaynakça

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