The objective of this investigation is to explore the correlation between hamstring tightness and physical performance, specifically vertical jump and dynamic balance, among youth basketball athletes. Based on our study's outcomes, the vertical jump test results exhibited an association with the left HF-KE angle and popliteal angle, while no significant correlation was found between the results of the right and left Y balance test and other parameters. However, through multiple regression analysis, a notable relationship between the performance of the right and left HF-KE and jumping performance was revealed.
The critical importance of vertical jumps in basketball is a fundamental requirement to ensure maximum performance through rapid muscle tension and reflexive contractions[6] [17]. Studies have reported that insufficient flexibility in the muscles leads to decreased jumping force. Domínguez-Díez et al. examined the relationship between passive joint mobility of the lower extremities and jumping performance in soccer and basketball young players. They found insufficient correlation between joint mobility and jumping performance, but concluded that it is a characteristic that needs to be evaluated and developed in these athletes [18]. In another study, Panoutsakopoulos et al. reported that mechanical energy transfer during a vertical jump is facilitated by dual-joint lower extremity muscles. They also reported that a flexible ankle joint contributes to higher jump performance in volleyball players, emphasizing the importance of flexibility in the hip, knee, and ankle joints during jumping [19].
In our study, we found a relationship between jumping performance and flexibility in both correlation and regression analysis results. However, existing studies examining the effect of hamstring flexibility on jumping performance in youth or professional basketball players are insufficient. Past studies in other sports have reported conflicting results regarding hamstring flexibility. Rey et al. conducted physical fitness tests, including jumping, in professional soccer players with low and high hamstring flexibility, finding no significant difference between the two groups [19]. We believe that the variation among studies is due to the different study populations, being composed of various amateur and professional athlete groups.
The positions of the lower extremities during jumping affect the jumping distance. Additionally, maintaining body stability is crucial. Therefore, proprioception and balance tests are important for athletes, alongside flexibility [20]. In a study investigating the effects of different jump directions on dynamic balance in the dominant and non-dominant legs, it was reported that vertical jumping is more suitable for evaluating dynamic postural stability. The dominant leg demonstrated better dynamic postural stability, associated with leg muscle strength [21]. In a study by Bogal et al., examining the impact of hamstring flexibility on vertical jump and balance, a relationship was found between left hamstring flexibility and jumping, but not with the right hamstring. However, no significant correlation was found between balance and hamstring flexibility [22]. Kramer et al. explored the relationship between dynamic balance measured by the Y Balance Test (YBT) and physical performance tests in high school students (aged 16–17), finding no significant relationship between YBT results for both legs and vertical jump [17]. In contrast to Demir et al.'s findings, moderate correlation was found between balance and hamstring tightness in children aged 10–12[23] .
Based on the available data, conflicting results have been reported regarding the relationship between hamstring flexibility and balance. Asan et al. found a particularly positive correlation between balance and flexibility averages, especially when the left foot was the balance foot in soccer players [24]. Similarly, in our study, we also identified a correlation between balance on the left foot and hamstring flexibility. This discrepancy may be attributed to the dominance of the right foot among the majority of participants, leading them to assume a supine position with the right foot grounded while balancing on the left foot.
Cejudo examined lower extremity flexibility in basketball players, determining hip flexion to be 78° and 83° during knee extension. Cejudo suggested that evaluating these flexibility measurements and asymmetries in a multi-component training program involving strength and neuromotor elements could prevent injuries. Additionally, investigating the impact of bilateral asymmetries in hip flexion range of motion during knee extension on physical performance is warranted [25]. In our study, the right hip flexion was determined to be 70.69, and the left was 77.48, indicating a similar asymmetry between extremities. This finding suggests the importance of a multicomponent training program and emphasizes the importance of asymmetric movement examination of athletes.