Rambling-trembling center-of-pressure decomposition reveals distinct sway responses to simulated somatosensory deficit.

BACKGROUND

Falls in older adults are often multifactorial, but can be linked to diminished sensation capabilities from age-related neural degeneration. Rambling-trembling (RM-TR) decomposition may provide insight into the relation between sensorineural function and postural sway, with both research and clinical applications.

RESEARCH QUESTION

What are the effects of perturbed somatosensation on RM-TR-derived measures of center of pressure (COP) during quiet standing?

METHODS

Fifty-two healthy young adults (22.10 ± 1.88 years) participated in the study. Participants stood on two force plates with a standardized stance width and foot angle, with eyes open (EO) or eyes closed (EC). Foam with different thicknesses ranging from 1/8″ to 1″ (F1-F4) was placed under the feet to interfere with intact sensory input and simulate varying degrees of somatosensory deficit. Force and moment data were used to calculate COP, RM, and TR time series. Mean velocity, acceleration, and jerk in the anteroposterior (AP) and mediolateral direction (ML) were extracted for comparison.

RESULTS

The EO condition remained relatively constant regardless of foam thickness. The EC condition showed increasing changes from baseline to each of the foam conditions. COP captures the smallest change in foam thickness, but RM provides a robustness across parameters that is not found in COP or TR. RM jerk in the AP direction showed significantly greater changes from baseline to F4 than the COP or TR counterparts. In the ML direction, TR jerk showed a sharper contrast between foam conditions than COP and RM.

SIGNIFICANCE

Findings suggest that RM-TR-derived measures may act as a compliment to, or provide a greater degree of sensitivity than, traditional COP measures and aid in the initial detection and monitoring of fall risk in aging and pathological populations.