. 2015 Sep 8;10:1847–1852. doi: 10.2147/COPD.S89814

Table 3.

Correlation matrix presenting the association between respiratory volumes and quadriceps contraction strength

	FVC (L)	FVC (%)	FEV₁ (L)	FEV₁ (%)	FEV₁/FVC
IKE left	0.620^**	0.551^**	0.573^**	0.618^**	0.506^**
IKE right	0.636^**	0.559^**	0.619^**	0.626^**	0.565^**

Notes: The strength of the correlations was assessed using Spearman’s correlation coefficient.

^**

Correlations are significant at 0.01 level.

Abbreviations: FVC, forced vital capacity; FEV₁, forced expiratory volume in 1 second; IKE, isometric knee extension.