Table 3. Quadriceps function and RMS of the SEMG during QMVC test (mean±SD).

Variables	Sex	Control (n = 60)	COPD (n = 71)	t value	P values
QMVC (kg)	male	42.06±7.61	23.25±5.70	11.58	<0.001
	female	29.24±4.58	15.55±4.25	10.83	<0.001
QTf (S)	male	81.09±22.58	51.13±18.15	5.87	<0.001
	female	83.44±23.64	56.31±15.49	5.09	<0.001
VL-RMS (mv)	male	405.76±82.52	294.77±89.27	4.93	<0.001
	female	306.13±63.13	218.94±48.95	5.06	<0.001
RF-RMS (mv)	male	334.35±104.72	239.89±89.75	3.90	<0.001
	female	252.19±53.47	173.46±73.72	4.50	<0.001
VM-RMS (mv)	male	345.77±66.56	274.13±81.00	3.60	<0.01
	female	281.52±75.15	188.35±53.51	4.62	<0.001

QMVC: quadriceps maximal volitional contraction; QTf: quadriceps time to fatigue; VL: vastus lateralis; RF-M: rectus femoris; VM: vastus medialis; RMS: root mean squares; RF: rectus femoris; RMS: root mean squares; SEMG: surface electromyography;