Postural control of trunk during unstable sitting.

Area of Science:

• Biomechanics
• Human Motor Control
• Rehabilitation Engineering

Background:

• Assessing lumbar spine postural control is crucial for understanding balance.
• Existing methods may not adequately isolate lumbar spine contributions.
• Unstable sitting provides a challenging environment to evaluate postural strategies.

Purpose of the Study:

• To develop and validate a novel method for quantifying lumbar spine and trunk postural control during unstable sitting.
• To investigate the relationship between postural control, task difficulty, and subject characteristics.
• To assess the repeatability of the developed measurement technique.

Main Methods:

• An unstable seat apparatus with adjustable difficulty (polyester hemispheres) was used.
• Leg and foot supports isolated lumbar and trunk control from lower body adjustments.
• Center of Pressure (CoP) data from a force plate were analyzed using summary statistics and random walk analysis.

Main Results:

• Center of Pressure (CoP) movement significantly increased with greater seat instability (p<0.01).
• Stabilogram analysis suggested distinct short-term (open-loop) and long-term (closed-loop) postural control mechanisms.
• Repeatability was excellent for summary statistics and short-term coefficients, fair for long-term diffusion, and poor for scaling exponents.

Conclusions:

• The developed method reliably quantifies lumbar spine postural control during challenging sitting tasks.
• Findings support the use of CoP analysis to differentiate between open and closed-loop postural control.
• This technique holds potential for evaluating postural deficits in populations like those with low-back pain.