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Process stationarity and reliability of trunk postural stability.
HyunWook Lee1, Kevin P Granata
1School of Biomedical Engineering and Sciences, Virginia Polytechnic Institute and State University, 219 Norris Hall (0219), Blacksburg, VA 24061, USA. hwlee@vt.edu
Clinical Biomechanics (Bristol, Avon)
|February 29, 2008
Summary
Torso stability assessment requires at least 30 seconds of data for reliable results. Nonlinear measures offer excellent reliability for seated balance tasks, particularly for inter-session comparisons.
Area of Science:
- Biomechanics
- Human Movement Science
- Motor Control
Background:
- Assessing torso stability is crucial for understanding seated balance.
- Current methods rely on postural variability and nonlinear analyses but need sufficient duration and reliability.
- This study aimed to determine the necessary trial duration and reliability of torso stability assessment.
Purpose of the Study:
- To establish the minimum trial duration for reliable torso stability assessment.
- To characterize the test-retest reliability of different torso stability measures.
- To identify optimal methods for seated balance analysis.
Main Methods:
- Recorded kinetic and kinematic data during seated balance on a wobbly seat pan.
- Evaluated stability using dynamic variability and nonlinear analyses.
- Determined minimum trial duration via process stationarity and measured reliability using intra-class correlations.
Main Results:
- A trial duration of 30.2 seconds was necessary for process stationarity.
- Multi-dimensional movement measures achieved stationarity faster.
- Movement variability showed moderate intra-session (ICC=0.64) and inter-session (ICC=0.42) reliability.
- Nonlinear measures, such as H(S) and Lyapunov exponents, demonstrated excellent inter-session reliability (up to ICC=0.83).
Conclusions:
- A minimum trial duration of 30 seconds is recommended for torso stability assessments.
- Intra-session reliability is moderate to excellent, but inter-session comparisons require more measurements.
- Nonlinear measures like H(S) and Lyapunov exponents are superior for both intra- and inter-session torso stability analysis.
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