Ultrasound assessment of rectus femoris muscle in rehabilitation patients with chronic obstructive pulmonary disease screened for sarcopenia: correlation of muscle size with quadriceps strength and fat-free mass.

Purpose: To determine the relationship of the size of the rectus femoris muscle, assessed by ultrasonography, with parameters of muscle strength and body composition that are commonly used in the case-finding of sarcopenia in rehabilitation patients with chronic obstructive pulmonary disease (COPD).

Methods: Cross-sectional pilot study of 18 men with severe COPD and 17 healthy controls.

Main Outcome Variables: cross-sectional area, thickness, and width of the non-dominant rectus femoris muscle obtained by ultrasound, muscle strength determined by voluntary maximum isometric contraction of the quadriceps muscle, and fat-free mass assessed by bioimpedance analysis.