The purpose of this study was to investigate normative and age-related differences in trunk and pelvis kinematics and intersegmental coordination during sagittal plane flexion-extension. Trunk and pelvis kinematics were recorded while 76 participants performed a maximal range of motion task in the sagittal plane. Cross-correlation was calculated to determine the phase lag between adjacent segment motion, and coupling angles were calculated using vector coding and classified into one of 4 coordination patterns: in-phase, antiphase, superior, and inferior phase. A 2-way mixed-model multivariate analysis of variance was used to compare lumbar spine and pelvis angular kinematics, phase lags, and cross-correlation coefficients between groups. Young participants exhibited greater trunk range of motion compared with middle-aged participants. The lumbar spine and pelvis were predominantly rotating with minimum phase lag during flexion and extension movement for both age groups, and differences in coordination between the groups were seen during hyperextension and return to upright position. In conclusion, middle-aged adults displayed lower range of motion but maintained similar movement patterns to young adults, which could be attributed to protective mechanisms. Healthy lumbar and pelvis movement patterns are important to understand and need to be quantified as a baseline, which can be used to develop rehabilitation protocols for individuals with spinal ailments.
Keywords: cross-correlations; spine biomechanics; vector coding.