Table 6.

Hierarchical linear regression models for pain, fatigue, and pain and fatigue predicting the perceived function outcome variables, FIQR-Function, MAF-ADL, and SF-36-PF, controlling for age, BMI, pain catastrophizing, fear of movement, anxiety, and depression

		FIQR-Function			MAF-ADL			SF36-PF
		Adj. R2	Change (Δ) in R2	p value R2 change	Adj. R2	Change (Δ) in R2	p value R2 change	Adj. R2	Change (Δ) in R2	p value R2 change
Step 1	Control variables	0.13 **			0.22 **			0.11 *
Step 2A: pain	Resting	0.29 **	0.16	<0.001	0.23**	0.01	0.11	0.17 **	0.06	0.01
	Movement	0.37 **	0.26	<0.001	0.32 **	0.1	<0.001	0.33 **	0.22	<0.001
	Change	0.15**	0.02	0.12	0.26 **	0.04	0.02	0.18 **	0.07	0.007
Step 2B: fatigue	Resting	0.29 **	0.16	<0.001	0.30 **	0.08	0.002	0.19 **	0.08	0.004
	Movement	0.31 **	0.18	<0.001	0.39 **	0.17	<0.001	0.22 **	0.03	0.001
	Change	0.13**	0	0.23	0.25**	0.03	0.33	0.12*	0.01	0.27
Step 3: pain and fatigue	Resting	0.32 **	0.11	0.03	0.29**	0.03	0.76	0.19**	0.08	0.28
	Movement	0.42 **	0.29	0.006	0.41 **	0.19	≤0.001	0.34**	0.23	0.1
	Change	0.14**	0.01	0.49	0.27**	0.05	0.15	0.17**	0.06	0.83

Control variables: age, body mass index (BMI), pain catastrophizing (PCS), fear of movement (TSK), anxiety (PROMIS Anxiety), and depression (PROMIS Depression). Resting, movement, and change scores entered into separate regression models for pain (step 2A), fatigue (step 2B), and pain and fatigue together (step 3).

Abbreviations: FIQR-Function Fibromyalgia Impact Questionnaire Revised - Function Subscale, MAF-ADL Multidimensional - Assessment of Fatigue Activities of Daily Living, SF-36-PF Short-Form Health Survey Physical Function

R² significance level: **p ≤ 0.01 level; *p ≤ 0.05 level