Table 3. Correlation matrix between the clinical indicators and ultrasound features.

Characteristics	AMSI (kg/m2)	Handgrip strength (kg)	6-m walking speed (m/s)
MT of the RFM in the relaxed state (cm)
r	0.515	0.463	0.292
P value	<0.001*	<0.001*	0.001*
CSA of the RFM in the relaxed state (cm2)
r	0.596	0.466	0.262
P value	<0.001*	<0.001*	0.002*
SWE of the RFM in the relaxed state (kPa)
r	0.107	0.082	0.109
P value	0.217	0.347	0.210
MT of the RFM in the contracted state (cm)
r	0.530	0.353	0.332
P value	<0.001*	<0.001*	<0.001*
CSA of the RFM in the contracted state (cm2)
r	0.509	0.448	0.285
P value	<0.001*	<0.001*	0.001*
SWE of the RFM in the contracted state (kPa)
r	−0.089	0.014	0.060
P value	0.306	0.869	0.494
MT of the GMM (cm)
r	0.361	0.373	0.165
P value	<0.001*	<0.001*	0.056
Fl of the GMM (cm)
r	0.260	0.278	0.202
P value	0.002*	0.001*	0.019*
PA of the GMM (°)
r	0.212	0.299	0.162
P value	0.014*	<0.001*	0.062
SWE of the GMM (kPa)
r	0.550	0.467	0.317
P value	<0.001*	<0.001*	<0.001*

*, a statistically significant difference. ASMI, appendicular skeletal muscle mass index; CSA, cross-sectional area; GMM, gastrocnemius medialis muscle; RFM, rectus femoris muscle; MT, muscle thickness; PA, pennation angle; Fl, fascicle length; SWE, shear-wave elastography.