The relationship between hamstring muscle extensibility and spinal postures varies with the degree of knee extension

The aim was to determine the relationship between hamstring muscle extensibility and sagittal spinal curvatures and pelvic tilt in cyclists while adopting several postures. A total of 75 male cyclists were recruited for this study (34.79 ± 9.46 years). Thoracic and lumbar spine and pelvic tilt were randomly measured using a Spinal Mouse. Hamstring muscle extensibility was determined in both legs by a passive knee extension test. Low relationships were found between hamstring muscle extensibility and spinal parameters (thoracic and lumbar curvature, and pelvic tilt) in standing, slumped sitting, and on the bicycle (r = .19; P > .05). Significant but low relationships were found in maximal trunk flexion with knees flexed (r = .29; P < .05). In addition, in the sit-and-reach test, low and statistically significant relationships were found between hamstring muscle extensibility for thoracic spine (r = -.23; P = .01) and (r = .37; P = .001) for pelvic tilt. In conclusion, hamstring muscle extensibility has a significant relationship in maximal trunk flexion postures with knees flexed and extended, but there are no relationships while standing or on the bicycle postures.