Table 4. Relationships and differences between 4MGS and 6MWD and other outcome measures in the study cohort.

	4MGS			6MWD
	r	P value		r	P value
Age, years	−0.207	0.145		−0.3111	0.0263
BMI, kg/m2	−0.2301	0.1043		−0.1067	0.4523
PaO2, mmHg	0.1502	0.2927		0.2888	0.0398
PaCO2, mmHg	0.1779	0.2118		0.2155	0.1289
VC, L	0.0625	0.6632		0.2541	0.072
%VC, %	−0.0148	0.9179		0.1949	0.1704
%FEV1/FVC	−0.0721	0.615		−0.1439	0.3137
%DLCO, %	0.244	0.0845		0.5137	0.0001
mMRC score	−0.3686	0.0078		−0.4421	0.0012
CAT score	−0.4132	0.0026		−0.5931	<0.0001
SGRQ-S	−0.3831	0.0055		−0.3962	0.004
SGRQ-A	−0.5206	<0.0001		−0.6628	<0.0001
SGRQ-I	−0.5013	0.0002		−0.5794	<0.0001
SGRQ-total	−0.5357	<0.0001		−0.6273	<0.0001
QF torque, Nm/kg	0.1979	0.1639		0.3516	0.0114
SMI	0.0105	0.9417		0.059	0.6811

4MGS, 4-m gait speed; 6MWD, 6-min walk distance; BMI, body mass index; PaO₂, arterial oxygen pressure; PaCO₂, arterial carbon dioxide pressure; VC, volume capacity; FEV₁, forced expiratory volume in 1 s; FVC, forced volume capacity; DLCO, diffusing capacity of carbon monoxide; mMRC, modified Medical Research Council; CAT, chronic obstructive pulmonary disease assessment test; SGRQ, St. George’s respiratory questionnaire; QF, quadriceps force; SMI, skeletal muscle mass index.