Table 2.
Descriptive statistics of physiological and patient-reported outcome variables at 3 assessment time points
| Baseline | After 2 Weeks | After 6 Weeks | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| n | Mean | SD | n | Mean | SD | n | Mean | SD | ||
| Physiological outcome variables | ||||||||||
| Lumbar spine stiffness | ||||||||||
| Palpatory | GS (N/mm) at L3 | 80 | 4.8 | 1.8 | 67 | 4.3 | 1.8 | 66 | 4.2 | 1.3 |
| GSV (N/mm) | 80 | 2.3 | 1.5 | 67 | 2.0 | 1.1 | 66 | 1.9 | 1.1 | |
| nGSV | 80 | 0.5 | 0.2 | 67 | 0.5 | 0.2 | 66 | 0.5 | 0.2 | |
| Hand-held | GS (N/mm) at L3 | 69 | 7.7 | 2.1 | 57 | 7.5 | 1.8 | 59 | 7.6 | 2.2 |
| GSV (N/mm) | 71 | 2.3 | 1.3 | 58 | 2.1 | 1.1 | 59 | 2.1 | 1.3 | |
| nGSV | 71 | 0.3 | 0.1 | 58 | 0.3 | 0.1 | 59 | 0.3 | 0.1 | |
| Automated | GS (N/mm) at Ant. | 55 | 5.2 | 1.5 | 43 | 5.3 | 1.4 | 45 | 5.3 | 1.5 |
| Flexion-relaxation ratio (FRR) | ||||||||||
| Flexion FRR | 76 | 4.7 | 3.7 | 69 | 5.8 | 5.4 | 66 | 5.5 | 5.6 | |
| Extension FRR | 76 | 9.2 | 9.5 | 69 | 10.4 | 11.6 | 66 | 9.4 | 10.5 | |
| Asymmetry in flexion FRR | 76 | 1.5 | 0.5 | 69 | 1.4 | 0.5 | 66 | 1.4 | 0.4 | |
| Asymmetry in extension FRR | 76 | 1.4 | 0.7 | 68 | 1.4 | 0.4 | 65 | 1.4 | 0.5 | |
| Patient-reported outcome variables | ||||||||||
| Average LBP during last 24 h | VAS (mm) | 82 | 46.1 | 18.1 | 70 | 34.2 | 21.7 | 68 | 25.6 | 25.4 |
| Roland Morris Disability Questionnaire | 82 | 9.5 | 4.3 | 70 | 6.9 | 4.3 | 68 | 4.8 | 4.0 | |
SD standard deviation, GS global stiffness, GSV global stiffness variation among five lumbar segments, nGSV normalized global stiffness variation (unitless), Ant. the most anterior point of the lumbar curvature in a prone posture, FRR flexion-relaxation ratio (unitless) pooled together for both EMG acquisition systems, VAS visual analog scale