Bailey Strand

Date of Award

January 2019

Document Type


Degree Name

Master of Science (MS)


Kinesiology & Public Health Education

First Advisor

Grant Tomkinson


Background: Measurement reliability has important decision-making implications for physical therapists and researchers when assessing individuals. Given that physical therapists often visually assess forward head posture (FHP) to guide treatment, the aims of this study were to quantify: (a) the reliability of indirect (visual) assessments of standing FHP in asymptomatic adults, and (b) the magnitude of the biological (postural) and technical errors involved.

Methods: A reliability analysis of two indirect assessments (visual assessments of real and 3D body scanned people) of FHP was undertaken. The sample comprised 10 physical therapists and 50 asymptomatic participants. Participants were scanned using the Vitus Smart 3D whole body scanner and visually assessed for FHP by the physical therapists. One week later, the physical therapists visually assessed the scanned images of the participants plus 15 duplicates, and two weeks later, the physical therapists and participants again presented with physical therapists repeating their visual assessments. Reliability (both intra- and inter- rater) of indirect assessments was determined by Cohen’s Kappa (κ). Total error was estimated as the unexplained error in repeated indirect assessments of real people (i.e., 1 minus the intra-rater κ for real people); technical error as the unexplained error in repeated visual assessments of scanned people (i.e., 1 minus the intra-rater  for scanned people); and biological error as the difference between the total and technical errors.

Results: The intra-rater reliability of indirect assessments of real and scanned people was moderate (κ [95%CI]: real, 0.45 [0.34, 0.56]); scan, 0.46 [0.39, 0.53]), while the inter-rater reliability was slight ( [95%CI]: real, −0.02 [−0.09, 0.05]; scan, 0.09 [0.06, 0.12]). Nearly all of the FHP error was due to technical error.

Conclusions: The intra- and inter- rater reliability of indirect assessments of standing FHP was moderate and slight, respectively. It appears that nearly all of the error in indirect assessments of FHP is due to technical error, highlighting that efforts to improve reliability should focus on minimizing technical errors.