Evaluation of the relationship between hamstring tightness and lumbar lordosis in amateur football players

Football is a sport with high physical demands, involving repetitive lower extremity movements such as changes of direction, sprinting, jumping, and sudden stops. These intense loads may lead to functional adaptations in structures that play a role in posture and movement control, especially the hamstring muscles, lumbar lordosis, and sagittal pelvic alignment. Integrative studies that evaluate the effects of football on the musculoskeletal system simultaneously and multi-dimensionally at the level of the spine, pelvis, and muscle tissue, and that combine radiological, elastographic, and clinical data, are limited in the literature. The aim of this study is to examine the lumbar lordosis, sagittal pelvic alignment, and hamstring muscle characteristics in actively licensed amateur male football players and to compare these parameters with healthy male individuals who are not actively licensed in sports and to reveal the possible effects of football on these anatomical structures. This study was conducted on two separate groups consisting of 50 licensed male amateur football players between the ages of 18 and 30 who actively play in the amateur football leagues of Kahramanmaraş province in the 2024-2025 season (Group A) and 50 healthy male individuals in the same age range who do not actively play licensed sports (Group B). Participants' age, height, weight, body mass index (BMI), dominant leg direction, and, additionally, license year information for football players were recorded. Musculoskeletal or neurological disease, lower extremity or lumbar region surgery, hamstring injury in the last six months, history of clinically significant low back pain in the last year, BMI ≥30, and systemic chronic diseases were determined as exclusion criteria. Four main data sets were created in the study: (1) radiographic measurements (lumbar lordosis and sagittal pelvic parameters), (2) hamstring muscle elasticity values obtained by Shear-Wave elastography (SWE), (3) demographic data (age, height, weight, BMI, license year, and dominant leg), and (4) clinical flexibility test results (active knee extension (AKE), straight leg raise (SLR), and sit-reach (SR)). All measurements were performed by the same operators according to standardized protocols. Subvariables of the data sets were compared between groups A and B with independent sample t-tests or Mann-Whitney U tests; within groups, relationships between the same or different data sets were evaluated with Pearson or Spearman correlation analyses. Dominant and non-dominant leg comparisons were made with the Wilcoxon test, and p < 0.05 was accepted as the statistical significance limit in all tests. In Group A, hamstring SWE values and clinical examination tests were generally significantly higher (p < 0.001), while in Group B, age (p < 0.05), body weight (p < 0.05) and BMI values (p < 0.01) were significantly higher. No significant difference was found between the two groups in terms of lumbar lordosis and sagittal pelvic parameters. Lumbar lordosis and sagittal pelvic parameters were generally significantly correlated in both groups, SWE values showed more significant correlations in Group A compared to Group B, and significant correlations were found between age-body weight (p < 0.05), body weight-height (p < 0.001) and body weight-BMI (p < 0.001) in both groups; moreover, all clinical tests were correlated with each other in both groups (p < 0.001). In both groups, no significant correlation was found between lumbar lordosis and sagittal pelvic parameters and SWE values, while positive correlations were observed between lumbar lordosis and age, body weight and BMI; pelvic incidence and body weight and height. A significant negative correlation was found between lumbar lordosis and flexibility tests only in Group B with AKE and SLR (p < 0.01). SWE values were not found to be associated with demographic data and flexibility tests in both groups. In Group A, a positive correlation was found between height and SR test (p < 0.001) and a negative correlation was found with BMI (p < 0.05); and in Group B, significant negative correlations were observed between age, body weight and BMI and clinical tests. In Group A, while the SWE value of Semimembranosus muscle was significantly higher in the dominant leg in individuals with dominant right leg and Semitendinosus muscle was significantly higher in individuals with dominant left leg (p < 0.05); no difference was found in other muscles and tests. In Group B, in right-dominant individuals, the Semimembranosus muscle was found to be significantly higher in the dominant leg (p < 0.01), while the Semitendinosus and Biceps Femoris muscles were found to be significantly higher in the non-dominant leg (p < 0.05 and p < 0.01, respectively). Flexibility tests performed on these individuals also showed a significant difference in favor of the dominant side (p < 0.05), and in left-dominant individuals, a significant difference was found in favor of the non-dominant side only in the SLR test (p < 0.01). While no significant difference was observed in terms of lumbar lordosis and sagittal pelvic parameters in football players compared to healthy individuals; both hamstring muscle stiffness and flexibility were significantly higher, indicating that sport-specific functional adaptations developed in this muscle group. The fact that no flexibility asymmetry was detected in football players in terms of leg dominance suggests that football provides a balanced functional adaptation in both legs; the presence of this asymmetry in healthy individuals indicates the complex functional nature of the hamstring muscle group. The fact that no significant relationship was detected between spinopelvic parameters and hamstring flexibility suggests that these anatomical structures are affected by different biomechanical mechanisms. Our findings confirmed the part of our hypothesis that 'hamstring muscle stiffness in football players would be higher compared to healthy individuals', but did not support the expected differences in spinopelvic parameters, indicating that football may lead to adaptive changes in the hamstring muscle tissue rather than the lumbar-pelvic structures. There is a need for further studies to investigate the long-term effects of these adaptations and their relationship with athlete performance using multidisciplinary methods.