Reliability and Measurement Error of the Qualitative Analysis of Single Leg Loading (QASLS) Tool For Unilateral Tasks

Area of Science:

• Biomechanics and Movement Science
• Clinical Assessment Tools
• Musculoskeletal Injury Prevention

Background:

• Movement quality is crucial for reducing musculoskeletal injury risk in clinical and sporting settings.
• Existing assessments often focus on bilateral or jumping movements, limiting unilateral task evaluation.
• Qualitative Analysis of Single Leg Loading (QASLS) is a novel tool for unilateral tasks using a dichotomous scoring system.

Purpose of the Study:

• To evaluate the intra- and inter-rater reliability of the QASLS tool.
• To assess within- and between-session reliability of QASLS for unilateral movement tasks.
• To provide data on measurement error and smallest detectable difference (SDD) for the QASLS tool.

Main Methods:

• A reliability study design was employed.
• Fifteen healthy females performed single leg squat (SLS) and single leg landing (SLL) tasks.
• QASLS scoring was conducted via video playback with data collected within and between sessions (7 days apart).
• Intra-class correlation coefficients (ICC), Kappa coefficients, and percentage of exact agreement (PEA%) were used for reliability analysis.

Main Results:

• Within-session reliability was good to moderate (ICC=0.67-0.87), and between-session reliability was moderate to excellent (ICC=0.69-0.93).
• Intra-rater agreement for compound QASLS scores was near perfect (k=0.85-1.00, PEA%=90-100%).
• Inter-rater agreement for compound scores showed variability (k=0.03-0.74, PEA%=43.3-90%), with lower values for SLL.

Conclusions:

• The QASLS tool exhibits moderate to excellent within- and between-session reliability for unilateral loading tasks.
• While intra-rater reliability is high, inter-rater agreement requires improvement.
• Rater education and training are recommended to enhance the overall reliability of the QASLS assessment.