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 5 Estimated regression coefficients from separate mixed-effects regression models of pain intensity and disability

		Pain intensity(visual analog scale, mm)			Disability score^a(Roland Morris Disability Questionnaire)
Physiological variables		Est.	SE	p	Est.	SE	p
Lumbar spine stiffness
Palpatory	Intercept	41.9	4.5	<0.001	2.0	2.7	0.45
	Visit	−1.4	0.2	<0.001	−0.4	0.04	<0.001
	GS (N/mm) at L3	0.7	0.9	0.44	0.3	0.2	0.09
	Intercept	42.9	3.0	<0.001	3.5	2.4	0.15
	Visit	−1.4	0.2	<0.001	−0.4	0.04	<0.001
	GSV (N/mm)	1.0	1.0	0.35	0.3	0.2	0.15
	Intercept	43.6	3.4	<0.001	3.8	2.4	0.11
	Visit	−1.4	0.2	<0.001	−0.4	0.04	<0.001
	nGSV	3.0	5.6	0.60	1.2	1.1	0.27
Hand-held	Intercept	45.4	6.6	<0.001	0.1	3.7	0.98
	Visit	−1.8	0.2	<0.001	−0.4	0.05	<0.001
	GS (N/mm) at L3	0.03	0.8	0.97	0.5	0.2	0.02
	Intercept	47.7	3.3	<0.001	7.6	2.3	0.002
	Visit	−1.8	0.2	<0.001	−0.4	0.05	<0.001
	GSV (N/mm)	−1.0	1.2	0.39	−0.1	0.2	0.59
	Intercept	47.1	3.5	<0.001	7.9	2.2	<0.001
	Visit	−1.8	0.2	<0.001	−0.4	0.05	<0.001
	nGSV	−5.8	10.1	0.57	−2.7	2.1	0.20
Automated	Intercept	52.3	6.8	<0.001	−2.1	4.3	0.62
	Visit	−1.4	0.3	<0.001	−0.4	0.05	<0.001
	GS (N/mm) at Ant.	−1.5	1.2	0.23	0.7	0.3	0.03
Flexion-relaxation ratio
Flexion FRR	Intercept	44.7	2.6	<0.001	10.0	0.6	<0.001
	Visit	−1.6	0.2	<0.001	−0.4	0.04	<0.001
	FRR	0.08	0.3	0.81	−0.2	0.06	0.02
Extension FRR	Intercept	45.2	2.6	<0.001	10.0	0.6	<0.001
	Visit	−1.5	0.2	<0.001	−0.4	0.04	<0.001
	FRR	0	0.2	0.96	−0.1	0.03	0.008
Asymmetry in flexion FRR	Intercept	44.1	3.7	<0.001	9.0	0.8	<0.001
	Visit	−1.5	0.2	<0.001	−0.4	0.04	<0.001
	FRR	0.7	2.2	0.76	0.1	0.43	0.75
Asymmetry in extension FRR	Intercept	42.6	3.8	<0.001	8.3	0.8	<0.001
	Visit	−1.6	0.2	<0.001	−0.4	0.04	<0.001
	FRR	1.9	2.3	0.42	0.6	0.5	0.16

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 (baseline, after 2 weeks, and after 6 weeks) on time-varying physiological covariates, SE standard error
^aAll palpatory stiffness models, hand-held GS and automated GS also adjusted for BMI

ISSN: 2662-7671