A Quiet Unstable Sitting Test to quantify core stability in clinical settings: Application to adults with ventral hernia.

Background: The abdominal core is comprised of the diaphragm, abdominal wall, and pelvic floor, and serves several important functions for balance, movement, and strength. Injury to this area, such as hernia, can have substantial impact. The Quiet Unstable Sitting Test involves individuals seated on the rounded surface of a BOSU® balance trainer placed on top of a force plate and situated on a flat, elevated surface.

Methods: An ordinal Quiet Unstable Sitting Test core stability score was calculated from center of pressure measurements, with 0 representing "normal" and < 0 indicating worsening stability. Hernia-Related Quality of Life survey summary scores were assessed (higher scores indicating better quality).

Findings: A developmental cohort of 32 was used to establish reliability and normative values for the Quiet Unstable Sitting Test. A control group of 32 participants (43.7 ± 16.2 yrs., BMI 29.0 ± 4.9, 66% Female) was then compared to 21 patients with hernia (56.2 ± 12.5 yrs., BMI 29.2 ± 6.3, 24% Female). Hernia patients had median composite score of -2 and median quality of life score of 66, versus median Quiet Unstable Sitting Test of -0.5 and median quality of life of 93 for controls (p ≤ 0.01). Quality of life and Quiet Unstable Sitting Test scores were not correlated (p > 0.05).

Interpretation: Hernia patients demonstrated significantly worse core stability and quality of life. These assessments were independent of one another across the entire population, indicating each measure's unique constructs of patient function. Core stability can be reliably measured in a clinical setting and may help with patient activation and rehabilitation.