Table 2– Dependence of quadriceps maximum voluntary contraction strength (QMVC) on anthropometric factors in chronic obstructive pulmonary disease (COPD)

	UK Healthy (n = 212)		UK and the Netherlands COPD (n = 591)
	Regression coefficient (95% CI)	p-value	Regression coefficient (95% CI)	p-value
Model constant (QMVC) kg	56.2 (15.1– 97.4)	0.008	19.6 (0.21–39.1)	0.048
Age yrs	-0.30 (-0.44– -0.16)	<0.001	-0.31 (-0.38– -0.24)	<0.001
Female/male sex	-3.42 (-7.28–0.42)	0.081	-2.60 (-4.43– -0.78)	0.005
Height cm	-0.15 (-0.40–0.11)	0.254	-2.47 (-13.44–8.49)	0.657
FFM kg	0.68 (0.45–0.91)	<0.001	0.81 (0.68–0.91)	<0.001
FEV₁ % pred			0.047 (0.013–0.082)	0.007
Model r²	0.51		0.52

Results of multiple linear regression analyses of healthy and COPD patients are shown. Regression coefficients indicate the change in QMVC force per unit change of each covariable indicated. Sex difference represents females compared with males. p-values <0.05 suggest a statistically independent determinant in the regression equation. Sex did not reach the predetermined level of significance when COPD cohorts were analysed separately. FFM: fat-free mass; FEV1: forced expiratory volume in 1 s; % pred; % predicted.