Evaluation of the within- and between-day intra-tester and inter-tester reliability of positioning subjects into neutral and lordotic sitting postures

Purpose: To assess the reliability of postural positioning in two different sitting postures (SP), within- and between-days, as well as intra-tester and inter-tester. Methods: Twenty six individuals were facilitated into lordotic (LSP) and neutral (NSP) SP on two different days by four physiotherapists, while kinematic data were collected. Intra-tester and inter-tester reliability were assessed using measures of relative reliability (intra-class correlation coefficients, ICC) and absolute reliability (standard error of measurement-SEM; minimal detectable change; mean difference; limits of agreement). Results: Substantial or almost perfect relative reliability (ICC >0.67), with very good absolute reliability (SEM <2.7°) was found for both intra- and inter-tester (within- and between-day) reliability. However, likely due to methodological variation affecting head angles on Day 2, the reliability of head/neck angles were poor (ICC as low as −0.11, SEM ≤5.71°). Conclusion: This study suggests that postural positioning of asymptomatic individuals into NSP and LSP can be performed with very good reliability for most spinal angles. Therefore, clinicians can have some confidence that positioning in SPs can be done reliably. However, while the degree of error is typically small, the small range of movement occurring at many spinal angles suggests that determining what is a clinically meaningful change in posture is difficult.