Reliability and validity of spinal coordination patterns during treadmill walking in persons with thoracic spine pain – a preliminary study

BACKGROUND Persons with low back pain fail to show the same transition as healthy individuals from in-phase to anti-phase rotation of the thorax and pelvis as walking speed increases. The purpose of this study was to determine if the relative phase of the thorax and pelvis during walking was a reliable (within day test-retest) and valid measure for persons with thoracic pain. METHODS The time series motion of the spine over C7, T8 and sacrum were measured at five treadmill walking speeds (0.67, 0.89, 1.12, 1.34, 1.56 m/s) in 19 persons with thoracic spine pain and 19 healthy control subjects. After a 20 minute rest, all tests were repeated. The average relative phases of the transverse plane rotation between C7-T8, C7-sacrum and T8-sacrum during a one-minute walk were calculated. The standard error of measurement (SEM) and the intra-class correlation coefficient (ICC) were used to estimate test-retest reliability. Three-way repeated measures analyses of variance were performed to determine the influence of group, walking speed and session on the relative phases. RESULTS The minimum transverse plane motion amplitudes, across all participants and speeds, for the C7-T8, C7-sacrum, and T8-sacrum were 2.9, 5.1 and 2.8 degrees, respectively. The C7-T8 relative phase changed little with speed. The C7-sacrum and T8-sacrum relative phases showed increases as subjects walked faster, but both groups had similar patterns of change. Only the C7-T8 relative phase at 0.67 and 0.89 m/s exhibited good reliability (ICC > 0.80, SEM 4.2-5.7, no significant time effects) for both groups. The C7-T8 and T8-sacrum relative phases demonstrated significant group by speed effects. CONCLUSIONS The C7-T8 relative phase showed reasonable reliability and some discrimination between groups, but changes in response to walking speed were small. The T8-sacrum relative phase showed some discriminative ability, but reliability was not adequate.