Short-term effect of a hamstring stretching program in hamstring extensibility and sagittal spinal curvatures in high school students

Abstract

Hamstring shortness and postural deformities are frequent in adolescents. For this reason, the purpose of this study was to analyse the influence of a shortterm stretching program in hamstring extensibility and sagittal spinal curvatures in high school students. Sixty-two male high school students aged 14-17 years old performed a 70 seconds hamstring stretching program (3 exercises) twice a week for five weeks during their physical education classes. Hamstring extensibility was measured by the straight leg raise test and sit-and-reach test. Thoracic and lumbar curves and pelvic inclination were measures in relaxed standing and in the sit-and-reach test. These measures were assessed before (pre-test) and after (post-test) the intervention program. Significant increases in the sit-and-reach score (d= 0.23) and in the straight leg raise angle (d= 0.85-0.90) were found. Sagittal spinal curvatures in standing showed no differences between pre- and post-test. In the maximal trunk flexion position during the sit-and-reach was detected a lower thoracic kyphosis and posterior pelvic tilt (p < 0.05) in post-test although with a low size effect (d=0.02-0.22). A hamstring muscle stretching program with a volume of 2 sessions per week (70 seconds each session), for 5 weeks, improves hamstring extensibility in adolescents and slightly reduces the thoracic bending and posterior pelvic tilt in trunk flexion postures with extended knees.