gms | German Medical Science

Objective: To determine whether the degree of hamstring muscle extensibility influences the sagittal spinal curvatures in standing, slumped sitting, and maximal trunk flexion with knees extended in young paddlers.

Material/Methods: A total of 128 young nationally ranked kayakers were recruited for this study (mean age: 15.43±0.67 years). The inclusion criteria were more than 4 years' paddling experience and training at least six times per week. The thoracic and lumbar angles and pelvic inclination were measured with a Spinal Mouse (Idiag, Volkerswill, Switzerland) in relaxed standing, slumped sitting, and maximal trunk flexion with knees extended (sit-and-reach test). The Spinal Mouse was guided along the midline of the spine (or slightly paravertebrally in particularly thin individuals with prominent processus spinous) starting at the processus spinous of C7 and finishing at the top of the anal crease (approximately S3). For each testing position, the thoracic (T1-2 to T11-12) and lumbar (T12-L1 to the sacrum) spine and the position of the sacrum and the hips (difference between the sacral angle and the vertical) were recorded. For the pelvic inclination, a positive value reflected an anterior pelvic tilt while a negative value reflected a posterior pelvic tilt. Hamstring muscle extensibility was determined in both legs by passive straight leg raise test (PSLR). The ankle of the tested leg was restrained in plantar flexion. The measurements were made in a randomized order. Only subjects with PSLR difference between right and left sides lower than 10% were included in the analysis (n=121). The left and right PSLR measurements were then averaged. After this, the sample was divided into three groups according to PSLR angle: (1) lower extensibility (Group A, PSLR <74º, n=45), (2) moderate extensibility (Group B, PSLR= 74º-86º, n=39), and (3) greater extensibility (Group C, PSLR >86º, n=37), and the dependent variables were analyzed.

Results: The mean values (± standard deviation) of passive straight leg raise test were 70.98±10.47º for lower hamstring extensibility group, 81.90±9.30º for moderate hamstring extensibility group, and 94.76±10.26º for greater extensibility group (p<0.001). No differences were found between groups for standing and slumped sitting in any dependent variable. The mean values for thoracic curvature in the sit-and-reach test were 60.22±12.27º, 54.62±10.84º, and 47.05±13.34º for groups A, B and C, respectively. The values of pelvic inclination were -13.56±9.23º, -7.03±8.94º, and 1.46±10.99º, for groups A, B and C, respectively. The ANOVA analysis showed significant differences between groups for thoracic (p<0.001) and pelvic (p<0.001) angles in sit-and-reach test. Post hoc analysis showed significant differences between all pairwise comparisons for pelvic angle and thoracic angle (p<0.001). However, no differences were found for lumbar curve.

Conclusion: The hamstring muscle extensibility influences the thoracic and pelvic postures when maximal trunk flexion is performed. The subjects with lower hamstring extensibility adopt greater kyphotic postures in the thoracic spine while the pelvis adopts greater posterior pelvic tilt postures. The hamstring extensibility has no influence in standing or slumped sitting because the hamstring muscle tension is reduced.