Association of lumbar spine stiffness and flexion-relaxation phenomenon with patient-reported outcomes in adults with chronic low back pain – a single-arm clinical trial investigating the effects of thrust spinal manipulation

Table 4 Estimated regression coefficients from separate mixed-effects regression models of physiological covariates over time

Physiological variables^a		Est.	SE	p
Lumbar spine stiffness
Palpatory
GS (N/mm) at L3	Intercept	5.51	0.71	<0.001
GS (N/mm) at L3	Visit	−0.048	0.020	0.02
GSV (N/mm)	Intercept	0.84	0.62	0.18
GSV (N/mm)	Visit	−0.036	0.018	0.04
nGSV	Intercept	0.13	0.11	0.27
nGSV	Visit	−0.003	0.003	0.29
Hand-held
GS (N/mm) at L3	Intercept	13.28	0.83	<0.001
GS (N/mm) at L3	Visit	−0.003	0.025	0.91
GSV (N/mm)	Intercept	1.78	0.65	0.01
GSV (N/mm)	Visit	−0.014	0.019	0.47
nGSV	Intercept	0.05	0.08	0.52
nGSV	Visit	−0.002	0.002	0.47
Automated
GS (N/mm) at Ant.	Intercept	8.49	0.79	<0.001
GS (N/mm) at Ant.	Visit	0.006	0.022	0.78
Flexion-relaxation ratio
Flexion FRR	Intercept	16.42	2.45	<0.001
Flexion FRR	Visit	0.091	0.073	0.22
Extension FRR	Intercept	41.65	5.20	<0.001
Extension FRR	Visit	0.036	0.150	0.81
Asymmetry in flexion FRR	Intercept	1.38	0.29	<0.001
Asymmetry in flexion FRR	Visit	−0.008	0.008	0.33
Asymmetry in extension FRR	Intercept	1.70	0.30	<0.001
Asymmetry in extension FRR	Visit	−0.001	0.009	0.89

GS global stiffness, L3 the 3rd lumbar segment, Ant. the most anterior point of the lumbar curvature in a prone posture, GSV global stiffness variation among five lumbar segments, nGSV normalized global stiffness variation (unitless), FRR flexion-relaxation ratio (unitless) pooled together for both EMG acquisition systems, Est. estimated regression coefficients from corresponding regression models over 3 assessment time points (at baseline, after 2 weeks, and after 6 weeks), SE standard error
^aAll models adjusted for sex, age and BMI

ISSN: 2662-7671